Makefile

@@ -38,7 +38,7 @@ SUPPORTED := ubuntu-20.04 \
 # These targets are the main ones to use for most things.
 ##
 
-.PHONY: all clean tgz lint format test query-tests install-common install-openrc install-systemd
+.PHONY: all clean tgz test query-tests install-common install-openrc install-systemd
 
 all: package-all
 
@@ -80,18 +80,6 @@ tgz:
 clean:
 	rm -rf $(BUILD_DIR)
 
-# Check for lint
-lint:
-	pylint src/pgmon.py
-	pylint src/test_pgmon.py
-	black --check --diff src/pgmon.py
-	black --check --diff src/test_pgmon.py
-
-# Format the code using black
-format:
-	black src/pgmon.py
-	black src/test_pylint.py
-
 # Run unit tests for the script
 test:
 	cd src ; python3 -m unittest

pylintrc

@@ -1,4 +0,0 @@
-[MASTER]
-py-version=3.5
-
-disable=fixme

sample-config/pgmon-metrics.yml

@@ -230,19 +230,7 @@ metrics:
         SELECT COUNT(*) FILTER (WHERE has_sequence_privilege(c.oid, 'SELECT,USAGE')) AS visible_sequences,
                COUNT(*) AS total_sequences
         FROM pg_class AS c
-        WHERE relkind = 'S'
-
-  locks:
-    type: row
-    query:
-      0:
-        SELECT COUNT(*) AS total,
-               SUM(CASE WHEN granted THEN 1 ELSE 0 END) AS granted
-        FROM pg_locks
-      90400: >
-        SELECT COUNT(*) AS total,
-               COUNT(*) FILTER (WHERE granted) AS granted
-        FROM pg_locks
+        WHERE relkind = 'S';
 
 
   ##

src/pgmon.py

@@ -1,50 +1,36 @@
 #!/usr/bin/env python3
-"""
-pgmon is a monitoring intermediary that sits between a PostgreSQL cluster and a monitoring systen
-that is capable of parsing JSON responses over an HTTP connection.
-"""
-
-# pylint: disable=too-few-public-methods
 
+import yaml
 import json
 import time
 import os
 import sys
-import signal
+
 import argparse
 import logging
-import re
-
-from decimal import Decimal
-
-from urllib.parse import urlparse, parse_qs
-
-from contextlib import contextmanager
 
 from datetime import datetime, timedelta
 
-from http.server import BaseHTTPRequestHandler
-from http.server import ThreadingHTTPServer
-
-from threading import Lock
-
-import yaml
-
 import psycopg2
 from psycopg2.extras import RealDictCursor
 from psycopg2.pool import ThreadedConnectionPool
 
-import requests
+from contextlib import contextmanager
 
+import signal
+from threading import Thread, Lock, Semaphore
+
+from http.server import BaseHTTPRequestHandler, HTTPServer
+from http.server import ThreadingHTTPServer
+from urllib.parse import urlparse, parse_qs
+
+import requests
+import re
+
+from decimal import Decimal
 
 VERSION = "1.0.4"
 
-
-class Context:
-    """
-    The global context for connections, config, version, nad IPC
-    """
-
 # Configuration
 config = {}
 
@@ -79,63 +65,41 @@ class Context:
 
 # Configure logging
 log = logging.getLogger(__name__)
-
-    @classmethod
-    def init_logging(cls):
-        """
-        Actually initialize the logging framework.  Since we don't ever instantiate the Context
-        class, this provides a way to make a few modifications to the log handler.
-        """
-
 formatter = logging.Formatter(
-            "%(asctime)s - %(levelname)s - %(filename)s: "
-            "%(funcName)s() line %(lineno)d: %(message)s"
+    "%(asctime)s - %(levelname)s - %(filename)s: %(funcName)s() line %(lineno)d: %(message)s"
 )
 console_log_handler = logging.StreamHandler()
 console_log_handler.setFormatter(formatter)
-        cls.log.addHandler(console_log_handler)
+log.addHandler(console_log_handler)
 
 
 # Error types
 class ConfigError(Exception):
-    """
-    Error type for all config related errors.
-    """
+    pass
 
 
 class DisconnectedError(Exception):
-    """
-    Error indicating a previously active connection to the database has been disconnected.
-    """
+    pass
 
 
 class UnhappyDBError(Exception):
-    """
-    Error indicating that a database the code has been asked to connect to is on the unhappy list.
-    """
+    pass
 
 
 class UnknownMetricError(Exception):
-    """
-    Error indicating that an undefined metric was requested.
-    """
+    pass
 
 
 class MetricVersionError(Exception):
-    """
-    Error indicating that there is no suitable query for a metric that was requested for the
-    version of PostgreSQL being monitored.
-    """
+    pass
 
 
 class LatestVersionCheckError(Exception):
-    """
-    Error indicating that there was a problem retrieving or parsing the latest version information.
-    """
+    pass
 
 
 # Default config settings
-DEFAULT_CONFIG = {
+default_config = {
     # The address the agent binds to
     "address": "127.0.0.1",
     # The port the agent listens on for requests
@@ -213,16 +177,27 @@ def update_deep(d1, d2):
     return d1
 
 
-def validate_metric(path, name, metric):
+def read_config(path, included=False):
     """
-    Validate a metric definition from a given file.  If any query definitions come from external
-    files, the metric dict will be updated with the actual query.
+    Read a config file.
 
-    Params:
-        path: path to the file which contains this definition
-        name: name of the metric
-        metric: the dictionary containing the metric definition
+    params:
+        path: path to the file to read
+        included: is this file included by another file?
     """
+    # Read config file
+    log.info("Reading log file: {}".format(path))
+    with open(path, "r") as f:
+        try:
+            cfg = yaml.safe_load(f)
+        except yaml.parser.ParserError as e:
+            raise ConfigError("Inavlid config file: {}: {}".format(path, e))
+
+    # Since we use it a few places, get the base directory from the config
+    config_base = os.path.dirname(path)
+
+    # Read any external queries and validate metric definitions
+    for name, metric in cfg.get("metrics", {}).items():
         # Validate return types
         try:
             if metric["type"] not in ["value", "row", "column", "set"]:
@@ -231,14 +206,14 @@ def validate_metric(path, name, metric):
                         metric["type"], name, path
                     )
                 )
-    except KeyError as e:
+        except KeyError:
             raise ConfigError(
                 "No type specified for metric {} in {}".format(name, path)
-        ) from e
+            )
 
         # Ensure queries exist
         query_dict = metric.get("query", {})
-    if not isinstance(query_dict, dict):
+        if type(query_dict) is not dict:
             raise ConfigError(
                 "Query definition should be a dictionary, got: {} for metric {} in {}".format(
                     query_dict, name, path
@@ -249,47 +224,22 @@ def validate_metric(path, name, metric):
             raise ConfigError("Missing queries for metric {} in {}".format(name, path))
 
         # Read external sql files and validate version keys
-    config_base = os.path.dirname(path)
         for vers, query in metric["query"].items():
             try:
                 int(vers)
-        except Exception as e:
+            except:
                 raise ConfigError(
                     "Invalid version: {} for metric {} in {}".format(vers, name, path)
-            ) from e
+                )
 
-        # Read in the external query and update the definition in the metricdictionary
             if query.startswith("file:"):
                 query_path = query[5:]
                 if not query_path.startswith("/"):
                     query_path = os.path.join(config_base, query_path)
-            with open(query_path, "r", encoding="utf-8") as f:
+                with open(query_path, "r") as f:
                     metric["query"][vers] = f.read()
 
-
-def read_config(path, included=False):
-    """
-    Read a config file.
-
-    params:
-        path: path to the file to read
-        included: is this file included by another file?
-    """
-
-    # Read config file
-    Context.log.info("Reading log file: %s", path)
-    with open(path, "r", encoding="utf-8") as f:
-        try:
-            cfg = yaml.safe_load(f)
-        except yaml.parser.ParserError as e:
-            raise ConfigError("Inavlid config file: {}: {}".format(path, e)) from e
-
-    # Read any external queries and validate metric definitions
-    for name, metric in cfg.get("metrics", {}).items():
-        validate_metric(path, name, metric)
-
     # Read any included config files
-    config_base = os.path.dirname(path)
     for inc in cfg.get("include", []):
         # Prefix relative paths with the directory from the current config
         if not inc.startswith("/"):
@@ -300,14 +250,14 @@ def read_config(path, included=False):
     # config
     if included:
         return cfg
-
+    else:
         new_config = {}
-    update_deep(new_config, DEFAULT_CONFIG)
+        update_deep(new_config, default_config)
         update_deep(new_config, cfg)
 
         # Minor sanity checks
         if len(new_config["metrics"]) == 0:
-        Context.log.error("No metrics are defined")
+            log.error("No metrics are defined")
             raise ConfigError("No metrics defined")
 
         # Validate the new log level before changing the config
@@ -320,17 +270,14 @@ def read_config(path, included=False):
         ]:
             raise ConfigError("Invalid log level: {}".format(new_config["log_level"]))
 
-    Context.config = new_config
+        global config
+        config = new_config
 
         # Apply changes to log level
-    Context.log.setLevel(logging.getLevelName(Context.config["log_level"].upper()))
-
-    # Return the config (mostly to make pylint happy, but also in case I opt to remove the side
-    # effect and make this more functional.
-    return Context.config
+        log.setLevel(logging.getLevelName(config["log_level"].upper()))
 
 
-def signal_handler(sig, frame):  # pylint: disable=unused-argument
+def signal_handler(sig, frame):
     """
     Function for handling signals
 
@@ -341,22 +288,19 @@ def signal_handler(sig, frame):  # pylint: disable=unused-argument
 
     # Signal everything to shut down
     if sig in [signal.SIGINT, signal.SIGTERM, signal.SIGQUIT]:
-        Context.log.info("Shutting down ...")
-        Context.running = False
-        if Context.httpd is not None:
-            Context.httpd.socket.close()
+        log.info("Shutting down ...")
+        global running
+        running = False
+        if httpd is not None:
+            httpd.socket.close()
 
     # Signal a reload
     if sig == signal.SIGHUP:
-        Context.log.warning("Received config reload signal")
-        read_config(Context.config_file)
+        log.warning("Received config reload signal")
+        read_config(config_file)
 
 
 class ConnectionPool(ThreadedConnectionPool):
-    """
-    Threaded connection pool that has a context manager.
-    """
-
     def __init__(self, dbname, minconn, maxconn, *args, **kwargs):
         # Make sure dbname isn't different in the kwargs
         kwargs["dbname"] = dbname
@@ -365,14 +309,7 @@ class ConnectionPool(ThreadedConnectionPool):
         self.name = dbname
 
     @contextmanager
-    def connection(self, timeout):
-        """
-        Connection context manager for our connection pool.  This will attempt to retrieve a
-        connection until the timeout is reached.
-
-        Params:
-            timeout: how long to keep trying to get a connection bedore giving up
-        """
+    def connection(self, timeout=None):
         conn = None
         timeout_time = datetime.now() + timedelta(timeout)
         # We will continue to try to get a connection slot until we time out
@@ -396,37 +333,34 @@ class ConnectionPool(ThreadedConnectionPool):
 def get_pool(dbname):
     """
     Get a database connection pool.
-
-    Params:
-        dbname: the name of the database for which a connection pool should be returned.
     """
     # Check if the db is unhappy and wants to be left alone
-    if dbname in Context.unhappy_cooldown:
-        if Context.unhappy_cooldown[dbname] > datetime.now():
+    if dbname in unhappy_cooldown:
+        if unhappy_cooldown[dbname] > datetime.now():
             raise UnhappyDBError()
 
     # Create a connection pool if it doesn't already exist
-    if dbname not in Context.connections:
-        with Context.connections_lock:
+    if dbname not in connections:
+        with connections_lock:
             # Make sure nobody created the pool while we were waiting on the
             # lock
-            if dbname not in Context.connections:
-                Context.log.info("Creating connection pool for: %s", dbname)
+            if dbname not in connections:
+                log.info("Creating connection pool for: {}".format(dbname))
                 # Actually create the connection pool
-                Context.connections[dbname] = ConnectionPool(
+                connections[dbname] = ConnectionPool(
                     dbname,
-                    int(Context.config["min_pool_size"]),
-                    int(Context.config["max_pool_size"]),
+                    int(config["min_pool_size"]),
+                    int(config["max_pool_size"]),
                     application_name="pgmon",
-                    host=Context.config["dbhost"],
-                    port=Context.config["dbport"],
-                    user=Context.config["dbuser"],
-                    connect_timeout=int(Context.config["connect_timeout"]),
-                    sslmode=Context.config["ssl_mode"],
+                    host=config["dbhost"],
+                    port=config["dbport"],
+                    user=config["dbuser"],
+                    connect_timeout=int(config["connect_timeout"]),
+                    sslmode=config["ssl_mode"],
                 )
             # Clear the unhappy indicator if present
-            Context.unhappy_cooldown.pop(dbname, None)
-    return Context.connections[dbname]
+            unhappy_cooldown.pop(dbname, None)
+    return connections[dbname]
 
 
 def handle_connect_failure(pool):
@@ -434,8 +368,8 @@ def handle_connect_failure(pool):
     Mark the database as being unhappy so we can leave it alone for a while
     """
     dbname = pool.name
-    Context.unhappy_cooldown[dbname] = datetime.now() + timedelta(
-        seconds=int(Context.config["reconnect_cooldown"])
+    unhappy_cooldown[dbname] = datetime.now() + timedelta(
+        seconds=int(config["reconnect_cooldown"])
     )
 
 
@@ -466,47 +400,42 @@ def json_encode_special(obj):
     """
     if isinstance(obj, Decimal):
         return float(obj)
-    raise TypeError("Cannot serialize object of {}".format(type(obj)))
+    raise TypeError(f"Cannot serialize object of {type(obj)}")
 
 
 def run_query_no_retry(pool, return_type, query, args):
     """
     Run the query with no explicit retry code
     """
-    with pool.connection(float(Context.config["connect_timeout"])) as conn:
+    with pool.connection(float(config["connect_timeout"])) as conn:
         try:
             with conn.cursor(cursor_factory=RealDictCursor) as curs:
-                output = None
                 curs.execute(query, args)
                 res = curs.fetchall()
 
                 if return_type == "value":
                     if len(res) == 0:
-                        output = ""
-                    output = str(list(res[0].values())[0])
+                        return ""
+                    return str(list(res[0].values())[0])
                 elif return_type == "row":
-                    # if len(res) == 0:
-                    #    return "[]"
-                    output = json.dumps(res[0], default=json_encode_special)
+                    if len(res) == 0:
+                        return "[]"
+                    return json.dumps(res[0], default=json_encode_special)
                 elif return_type == "column":
-                    # if len(res) == 0:
-                    #    return "[]"
-                    output = json.dumps(
+                    if len(res) == 0:
+                        return "[]"
+                    return json.dumps(
                         [list(r.values())[0] for r in res], default=json_encode_special
                     )
                 elif return_type == "set":
-                    output = json.dumps(res, default=json_encode_special)
-                else:
-                    raise ConfigError(
-                        "Invalid query return type: {}".format(return_type)
-                    )
-                return output
-        except Exception as e:
+                    return json.dumps(res, default=json_encode_special)
+        except:
             dbname = pool.name
-            if dbname in Context.unhappy_cooldown:
-                raise UnhappyDBError() from e
-            if conn.closed != 0:
-                raise DisconnectedError() from e
+            if dbname in unhappy_cooldown:
+                raise UnhappyDBError()
+            elif conn.closed != 0:
+                raise DisconnectedError()
+            else:
                 raise
 
 
@@ -528,7 +457,7 @@ def run_query(pool, return_type, query, args):
     try:
         return run_query_no_retry(pool, return_type, query, args)
     except DisconnectedError:
-        Context.log.warning("Stale PostgreSQL connection found ... trying again")
+        log.warning("Stale PostgreSQL connection found ... trying again")
         # This sleep is an annoying hack to give the pool workers time to
         # actually mark the connection, otherwise it can be given back in the
         # next connection() call
@@ -536,9 +465,9 @@ def run_query(pool, return_type, query, args):
         time.sleep(1)
         try:
             return run_query_no_retry(pool, return_type, query, args)
-        except Exception as e:
+        except:
             handle_connect_failure(pool)
-            raise UnhappyDBError() from e
+            raise UnhappyDBError()
 
 
 def get_cluster_version():
@@ -546,39 +475,40 @@ def get_cluster_version():
     Get the PostgreSQL version if we don't already know it, or if it's been
     too long sice the last time it was checked.
     """
+    global cluster_version
+    global cluster_version_next_check
 
     # If we don't know the version or it's past the recheck time, get the
     # version from the database.  Only one thread needs to do this, so they all
     # try to grab the lock, and then make sure nobody else beat them to it.
     if (
-        Context.cluster_version is None
-        or Context.cluster_version_next_check is None
-        or Context.cluster_version_next_check < datetime.now()
+        cluster_version is None
+        or cluster_version_next_check is None
+        or cluster_version_next_check < datetime.now()
     ):
-        with Context.cluster_version_lock:
+        with cluster_version_lock:
             # Only check if nobody already got the version before us
             if (
-                Context.cluster_version is None
-                or Context.cluster_version_next_check is None
-                or Context.cluster_version_next_check < datetime.now()
+                cluster_version is None
+                or cluster_version_next_check is None
+                or cluster_version_next_check < datetime.now()
             ):
-                Context.log.info("Checking PostgreSQL cluster version")
-                pool = get_pool(Context.config["dbname"])
-                Context.cluster_version = int(
+                log.info("Checking PostgreSQL cluster version")
+                pool = get_pool(config["dbname"])
+                cluster_version = int(
                     run_query(pool, "value", "SHOW server_version_num", None)
                 )
-                Context.cluster_version_next_check = datetime.now() + timedelta(
-                    seconds=int(Context.config["version_check_period"])
+                cluster_version_next_check = datetime.now() + timedelta(
+                    seconds=int(config["version_check_period"])
                 )
-                Context.log.info(
-                    "Got PostgreSQL cluster version: %s", Context.cluster_version
+                log.info("Got PostgreSQL cluster version: {}".format(cluster_version))
+                log.debug(
+                    "Next PostgreSQL cluster version check will be after: {}".format(
+                        cluster_version_next_check
                     )
-                Context.log.debug(
-                    "Next PostgreSQL cluster version check will be after: %s",
-                    Context.cluster_version_next_check,
                 )
 
-    return Context.cluster_version
+    return cluster_version
 
 
 def version_num_to_release(version_num):
@@ -591,6 +521,7 @@ def version_num_to_release(version_num):
     """
     if version_num // 10000 < 10:
         return version_num // 10000 + (version_num % 10000 // 100 / 10)
+    else:
         return version_num // 10000
 
 
@@ -599,7 +530,7 @@ def parse_version_rss(raw_rss, release):
     Parse the raw RSS from the versions.rss feed to extract the latest version of
     PostgreSQL that's availabe for the cluster being monitored.
 
-    This sets these Context variables:
+    This sets these global variables:
         latest_version
         release_supported
 
@@ -609,6 +540,8 @@ def parse_version_rss(raw_rss, release):
         raw_rss: The raw rss text from versions.rss
         release: The PostgreSQL release we care about (ex: 9.2, 14)
     """
+    global latest_version
+    global release_supported
 
     # Regular expressions for parsing the RSS document
     version_line = re.compile(
@@ -628,75 +561,75 @@ def parse_version_rss(raw_rss, release):
             version = m.group(1)
             parts = list(map(int, version.split(".")))
             if parts[0] < 10:
-                Context.latest_version = int(
+                latest_version = int(
                     "{}{:02}{:02}".format(parts[0], parts[1], parts[2])
                 )
             else:
-                Context.latest_version = int("{}00{:02}".format(parts[0], parts[1]))
+                latest_version = int("{}00{:02}".format(parts[0], parts[1]))
         elif release_found:
             # The next line after the version tells if the version is supported
             if unsupported_line.match(line):
-                Context.release_supported = False
+                release_supported = False
             else:
-                Context.release_supported = True
+                release_supported = True
             break
 
     # Make sure we actually found it
     if not release_found:
         raise LatestVersionCheckError("Current release ({}) not found".format(release))
 
-    Context.log.info(
-        "Got latest PostgreSQL version: %s supported=%s",
-        Context.latest_version,
-        Context.release_supported,
+    log.info(
+        "Got latest PostgreSQL version: {} supported={}".format(
+            latest_version, release_supported
+        )
+    )
+    log.debug(
+        "Next latest PostgreSQL version check will be after: {}".format(
+            latest_version_next_check
         )
-    Context.log.debug(
-        "Next latest PostgreSQL version check will be after: %s",
-        Context.latest_version_next_check,
     )
 
 
 def get_latest_version():
     """
-    Get the latest supported version of the major PostgreSQL release running on the server being
-    monitored.
+    Get the latest supported version of the major PostgreSQL release running on the server being monitored.
     """
 
+    global latest_version_next_check
+
     # If we don't know the latest version or it's past the recheck time, get the
     # version from the PostgreSQL RSS feed.  Only one thread needs to do this, so
     # they all try to grab the lock, and then make sure nobody else beat them to it.
     if (
-        Context.latest_version is None
-        or Context.latest_version_next_check is None
-        or Context.latest_version_next_check < datetime.now()
+        latest_version is None
+        or latest_version_next_check is None
+        or latest_version_next_check < datetime.now()
     ):
         # Note: we get the cluster version here before grabbing the latest_version_lock
         #       lock so it's not held while trying to talk with the DB.
         release = version_num_to_release(get_cluster_version())
 
-        with Context.latest_version_lock:
+        with latest_version_lock:
             # Only check if nobody already got the version before us
             if (
-                Context.latest_version is None
-                or Context.latest_version_next_check is None
-                or Context.latest_version_next_check < datetime.now()
+                latest_version is None
+                or latest_version_next_check is None
+                or latest_version_next_check < datetime.now()
             ):
-                Context.log.info("Checking latest PostgreSQL version")
-                Context.latest_version_next_check = datetime.now() + timedelta(
-                    seconds=int(Context.config["latest_version_check_period"])
+                log.info("Checking latest PostgreSQL version")
+                latest_version_next_check = datetime.now() + timedelta(
+                    seconds=int(config["latest_version_check_period"])
                 )
 
                 # Grab the RSS feed
-                raw_rss = requests.get(
-                    "https://www.postgresql.org/versions.rss", timeout=30
-                )
+                raw_rss = requests.get("https://www.postgresql.org/versions.rss")
                 if raw_rss.status_code != 200:
-                    raise LatestVersionCheckError("code={}".format(raw_rss.status_code))
+                    raise LatestVersionCheckError("code={}".format(r.status_code))
 
-                # Parse the RSS body and set Context variables
+                # Parse the RSS body and set global variables
                 parse_version_rss(raw_rss.text, release)
 
-    return Context.latest_version
+    return latest_version
 
 
 def sample_metric(dbname, metric_name, args, retry=True):
@@ -705,9 +638,9 @@ def sample_metric(dbname, metric_name, args, retry=True):
     """
     # Get the metric definition
     try:
-        metric = Context.config["metrics"][metric_name]
-    except KeyError as e:
-        raise UnknownMetricError("Unknown metric: {}".format(metric_name)) from e
+        metric = config["metrics"][metric_name]
+    except KeyError:
+        raise UnknownMetricError("Unknown metric: {}".format(metric_name))
 
     # Get the connection pool for the database, or create one if it doesn't
     # already exist.
@@ -722,6 +655,7 @@ def sample_metric(dbname, metric_name, args, retry=True):
     # Execute the quert
     if retry:
         return run_query(pool, metric["type"], query, args)
+    else:
         return run_query_no_retry(pool, metric["type"], query, args)
 
 
@@ -730,9 +664,9 @@ def test_queries():
     Run all of the metric queries against a database and check the results
     """
     # We just use the default db for tests
-    dbname = Context.config["dbname"]
+    dbname = config["dbname"]
     # Loop through all defined metrics.
-    for name, metric in Context.config["metrics"].items():
+    for name, metric in config["metrics"].items():
         # If the metric has arguments to use while testing, grab those
         args = metric.get("test_args", {})
         print(
@@ -777,8 +711,9 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
         """
         Override to suppress standard request logging
         """
+        pass
 
-    def do_GET(self):  # pylint: disable=invalid-name
+    def do_GET(self):
         """
         Handle a request.  This is just a wrapper around the actual handler
         code to keep things more readable.
@@ -786,7 +721,7 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
         try:
             self._handle_request()
         except BrokenPipeError:
-            Context.log.error("Client disconnected, exiting handler")
+            log.error("Client disconnected, exiting handler")
 
     def _handle_request(self):
         """
@@ -799,6 +734,7 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
 
         if metric_name == "agent_version":
             self._reply(200, VERSION)
+            return
         elif metric_name == "latest_version_info":
             try:
                 get_latest_version()
@@ -806,40 +742,46 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
                     200,
                     json.dumps(
                         {
-                            "latest": Context.latest_version,
-                            "supported": 1 if Context.release_supported else 0,
+                            "latest": latest_version,
+                            "supported": 1 if release_supported else 0,
                         }
                     ),
                 )
             except LatestVersionCheckError as e:
-                Context.log.error(
-                    "Failed to retrieve latest version information: %s", e
-                )
+                log.error("Failed to retrieve latest version information: {}".format(e))
                 self._reply(503, "Failed to retrieve latest version info")
-        else:
+            return
+
         # Note: parse_qs returns the values as a list.  Since we always expect
         #       single values, just grab the first from each.
         args = {key: values[0] for key, values in parsed_query.items()}
 
         # Get the dbname.  If none was provided, use the default from the
         # config.
-            dbname = args.get("dbname", Context.config["dbname"])
+        dbname = args.get("dbname", config["dbname"])
 
         # Sample the metric
         try:
             self._reply(200, sample_metric(dbname, metric_name, args))
-            except UnknownMetricError:
-                Context.log.error("Unknown metric: %s", metric_name)
+            return
+        except UnknownMetricError as e:
+            log.error("Unknown metric: {}".format(metric_name))
             self._reply(404, "Unknown metric")
-            except MetricVersionError:
-                Context.log.error("Failed to find an query version for %s", metric_name)
+            return
+        except MetricVersionError as e:
+            log.error(
+                "Failed to find a version of {} for {}".format(metric_name, version)
+            )
             self._reply(404, "Unsupported version")
-            except UnhappyDBError:
-                Context.log.info("Database %s is unhappy, please be patient", dbname)
+            return
+        except UnhappyDBError as e:
+            log.info("Database {} is unhappy, please be patient".format(dbname))
             self._reply(503, "Database unavailable")
-            except Exception as e:  # pylint: disable=broad-exception-caught
-                Context.log.error("Error running query: %s", e)
+            return
+        except Exception as e:
+            log.error("Error running query: {}".format(e))
             self._reply(500, "Unexpected error: {}".format(e))
+            return
 
     def _reply(self, code, content):
         """
@@ -852,14 +794,7 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
         self.wfile.write(bytes(content, "utf-8"))
 
 
-def main():
-    """
-    Main application routine
-    """
-
-    # Initialize the logging framework
-    Context.init_logging()
-
+if __name__ == "__main__":
     # Handle cli args
     parser = argparse.ArgumentParser(
         prog="pgmon", description="A PostgreSQL monitoring agent"
@@ -880,35 +815,33 @@ def main():
     args = parser.parse_args()
 
     # Set the config file path
-    Context.config_file = args.config_file
+    config_file = args.config_file
 
     # Read the config file
-    read_config(Context.config_file)
+    read_config(config_file)
 
     # Run query tests and exit if test mode is enabled
     if args.test:
-        if test_queries() > 0:
+        errors = test_queries()
+        if errors > 0:
             sys.exit(1)
+        else:
             sys.exit(0)
 
     # Set up the http server to receive requests
-    server_address = (Context.config["address"], Context.config["port"])
-    Context.httpd = ThreadingHTTPServer(server_address, SimpleHTTPRequestHandler)
+    server_address = (config["address"], config["port"])
+    httpd = ThreadingHTTPServer(server_address, SimpleHTTPRequestHandler)
 
     # Set up the signal handler
     signal.signal(signal.SIGINT, signal_handler)
     signal.signal(signal.SIGHUP, signal_handler)
 
     # Handle requests.
-    Context.log.info("Listening on port %s...", Context.config["port"])
-    while Context.running:
-        Context.httpd.handle_request()
+    log.info("Listening on port {}...".format(config["port"]))
+    while running:
+        httpd.handle_request()
 
     # Clean up PostgreSQL connections
     # TODO: Improve this ... not sure it actually closes all the connections cleanly
-    for pool in Context.connections.values():
+    for pool in connections.values():
         pool.close()
-
-
-if __name__ == "__main__":
-    main()

src/test_pgmon.py

@@ -1,12 +1,5 @@
-"""
-Unit tests for pgmon
-"""
-
-# pylint: disable=too-many-lines
-
 import unittest
 
-import os
 from datetime import datetime, timedelta
 import tempfile
 
@@ -20,7 +13,7 @@ import pgmon
 # Silence most logging output
 logging.disable(logging.CRITICAL)
 
-VERSIONS_RSS = """
+versions_rss = """
 <?xml version="1.0" encoding="utf-8"?>
 <rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>PostgreSQL latest versions</title><link>https://www.postgresql.org/</link><description>PostgreSQL latest versions</description><atom:link href="https://www.postgresql.org/versions.rss" rel="self"/><language>en-us</language><lastBuildDate>Thu, 08 May 2025 00:00:00 +0000</lastBuildDate><item><title>17.5
 </title><link>https://www.postgresql.org/docs/17/release-17-5.html</link><description>17.5 is the latest release in the 17 series.
@@ -110,18 +103,12 @@ This version is unsupported!
 """
 
 
-class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-methods
-    """
-    Unit test class for pgmon
-    """
-
+class TestPgmonMethods(unittest.TestCase):
     ##
     # update_deep
     ##
     def test_update_deep__empty_cases(self):
-        """
-        Test various empty dictionary permutations
-        """
+        # Test empty dict cases
         d1 = {}
         d2 = {}
         pgmon.update_deep(d1, d2)
@@ -141,9 +128,7 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
         self.assertEqual(d2, d1)
 
     def test_update_deep__scalars(self):
-        """
-        Test adding/updating scalar values
-        """
+        # Test adding/updating scalar values
         d1 = {"foo": 1, "bar": "text", "hello": "world"}
         d2 = {"foo": 2, "baz": "blah"}
         pgmon.update_deep(d1, d2)
@@ -151,9 +136,7 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
         self.assertEqual(d2, {"foo": 2, "baz": "blah"})
 
     def test_update_deep__lists(self):
-        """
-        Test adding to lists
-        """
+        # Test adding to lists
         d1 = {"lst1": []}
         d2 = {"lst1": [1, 2]}
         pgmon.update_deep(d1, d2)
@@ -189,9 +172,7 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
         self.assertEqual(d2, {"obj1": {"l1": [3, 4]}})
 
     def test_update_deep__dicts(self):
-        """
-        Test adding to dictionaries
-        """
+        # Test adding to lists
         d1 = {"obj1": {}}
         d2 = {"obj1": {"a": 1, "b": 2}}
         pgmon.update_deep(d1, d2)
@@ -218,9 +199,7 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
         self.assertEqual(d2, {"obj1": {"d1": {"a": 5, "c": 12}}})
 
     def test_update_deep__types(self):
-        """
-        Test mismatched types
-        """
+        # Test mismatched types
         d1 = {"foo": 5}
         d2 = None
         self.assertRaises(TypeError, pgmon.update_deep, d1, d2)
@@ -239,19 +218,15 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
     ##
 
     def test_get_pool__simple(self):
-        """
-        Test getting a pool in a normal case
-        """
-        pgmon.Context.config.update(pgmon.DEFAULT_CONFIG)
+        # Just get a pool in a normal case
+        pgmon.config.update(pgmon.default_config)
         pool = pgmon.get_pool("postgres")
         self.assertIsNotNone(pool)
 
     def test_get_pool__unhappy(self):
-        """
-        Test getting an unhappy database pool
-        """
-        pgmon.Context.config.update(pgmon.DEFAULT_CONFIG)
-        pgmon.Context.unhappy_cooldown["postgres"] = datetime.now() + timedelta(60)
+        # Test getting an unhappy database pool
+        pgmon.config.update(pgmon.default_config)
+        pgmon.unhappy_cooldown["postgres"] = datetime.now() + timedelta(60)
         self.assertRaises(pgmon.UnhappyDBError, pgmon.get_pool, "postgres")
 
         # Test getting a different database when there's an unhappy one
@@ -263,37 +238,30 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
     ##
 
     def test_handle_connect_failure__simple(self):
-        """
-        Test adding to an empty unhappy list
-        """
-        pgmon.Context.config.update(pgmon.DEFAULT_CONFIG)
-        pgmon.Context.unhappy_cooldown = {}
+        # Test adding to an empty unhappy list
+        pgmon.config.update(pgmon.default_config)
+        pgmon.unhappy_cooldown = {}
         pool = pgmon.get_pool("postgres")
         pgmon.handle_connect_failure(pool)
-        self.assertGreater(pgmon.Context.unhappy_cooldown["postgres"], datetime.now())
+        self.assertGreater(pgmon.unhappy_cooldown["postgres"], datetime.now())
 
         # Test adding another database
         pool = pgmon.get_pool("template0")
         pgmon.handle_connect_failure(pool)
-        self.assertGreater(pgmon.Context.unhappy_cooldown["postgres"], datetime.now())
-        self.assertGreater(pgmon.Context.unhappy_cooldown["template0"], datetime.now())
-        self.assertEqual(len(pgmon.Context.unhappy_cooldown), 2)
+        self.assertGreater(pgmon.unhappy_cooldown["postgres"], datetime.now())
+        self.assertGreater(pgmon.unhappy_cooldown["template0"], datetime.now())
+        self.assertEqual(len(pgmon.unhappy_cooldown), 2)
 
     ##
     # get_query
     ##
 
     def test_get_query__basic(self):
-        """
-        Test getting a query with just a default version.
-        """
+        # Test getting a query with one version
         metric = {"type": "value", "query": {0: "DEFAULT"}}
         self.assertEqual(pgmon.get_query(metric, 100000), "DEFAULT")
 
     def test_get_query__versions(self):
-        """
-        Test getting queries when multiple versions are present.
-        """
         metric = {"type": "value", "query": {0: "DEFAULT", 110000: "NEW"}}
 
         # Test getting the default version of a query with no lower bound and a newer
@@ -313,9 +281,6 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
         self.assertEqual(pgmon.get_query(metric, 100000), "OLD")
 
     def test_get_query__missing_version(self):
-        """
-        Test trying to get a query that is not defined for the requested version.
-        """
         metric = {"type": "value", "query": {96000: "OLD", 110000: "NEW", 150000: ""}}
 
         # Test getting a metric that only exists for newer versions
@@ -329,16 +294,11 @@ class TestPgmonMethods(unittest.TestCase):  # pylint: disable=too-many-public-me
     ##
 
     def test_read_config__simple(self):
-        """
-        Test reading a simple config.
-        """
-        pgmon.Context.config = {}
+        pgmon.config = {}
 
         # Test reading just a metric and using the defaults for everything else
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 # This is a comment!
@@ -350,20 +310,18 @@ metrics:
 """
                 )
 
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
         self.assertEqual(
-            pgmon.Context.config["max_pool_size"], pgmon.DEFAULT_CONFIG["max_pool_size"]
+            pgmon.config["max_pool_size"], pgmon.default_config["max_pool_size"]
         )
-        self.assertEqual(pgmon.Context.config["dbuser"], pgmon.DEFAULT_CONFIG["dbuser"])
+        self.assertEqual(pgmon.config["dbuser"], pgmon.default_config["dbuser"])
 
-        pgmon.Context.config = {}
+        pgmon.config = {}
 
         # Test reading a basic config
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 # This is a comment!
@@ -399,27 +357,22 @@ metrics:
 """
                 )
 
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
-        self.assertEqual(pgmon.Context.config["dbuser"], "someone")
-        self.assertEqual(pgmon.Context.config["metrics"]["test1"]["type"], "value")
-        self.assertEqual(pgmon.Context.config["metrics"]["test1"]["query"][0], "TEST1")
-        self.assertEqual(pgmon.Context.config["metrics"]["test2"]["query"][0], "TEST2")
+        self.assertEqual(pgmon.config["dbuser"], "someone")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["type"], "value")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
+        self.assertEqual(pgmon.config["metrics"]["test2"]["query"][0], "TEST2")
 
     def test_read_config__include(self):
-        """
-        Test including one config from another.
-        """
-        pgmon.Context.config = {}
+        pgmon.config = {}
 
         # Test reading a config that includes other files (absolute and relative paths,
         # multiple levels)
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
-                    """---
+                    f"""---
 # This is a comment!
 min_pool_size: 1
 max_pool_size: 2
@@ -431,17 +384,13 @@ reconnect_cooldown: 15
 version_check_period: 3600
 include:
   - dbsettings.yml
-  - {}/metrics.yml
-""".format(
-                        tmpdirname
-                    )
+  - {tmpdirname}/metrics.yml
+"""
                 )
 
-            with open(
-                os.path.join(tmpdirname, "dbsettings.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/dbsettings.yml", "w") as f:
                 f.write(
-                    """---
+                    f"""---
 dbuser: someone
 dbhost: localhost
 dbport: 5555
@@ -449,11 +398,9 @@ dbname: template0
 """
                 )
 
-            with open(
-                os.path.join(tmpdirname, "metrics.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/metrics.yml", "w") as f:
                 f.write(
-                    """---
+                    f"""---
 metrics:
   test1:
     type: value
@@ -468,11 +415,9 @@ include:
 """
                 )
 
-            with open(
-                os.path.join(tmpdirname, "more_metrics.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/more_metrics.yml", "w") as f:
                 f.write(
-                    """---
+                    f"""---
 metrics:
   test3:
     type: value
@@ -480,25 +425,20 @@ metrics:
       0: TEST3
 """
                 )
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
-        self.assertEqual(pgmon.Context.config["max_idle_time"], 10)
-        self.assertEqual(pgmon.Context.config["dbuser"], "someone")
-        self.assertEqual(pgmon.Context.config["metrics"]["test1"]["query"][0], "TEST1")
-        self.assertEqual(pgmon.Context.config["metrics"]["test2"]["query"][0], "TEST2")
-        self.assertEqual(pgmon.Context.config["metrics"]["test3"]["query"][0], "TEST3")
+        self.assertEqual(pgmon.config["max_idle_time"], 10)
+        self.assertEqual(pgmon.config["dbuser"], "someone")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
+        self.assertEqual(pgmon.config["metrics"]["test2"]["query"][0], "TEST2")
+        self.assertEqual(pgmon.config["metrics"]["test3"]["query"][0], "TEST3")
 
     def test_read_config__reload(self):
-        """
-        Test reloading a config.
-        """
-        pgmon.Context.config = {}
+        pgmon.config = {}
 
         # Test rereading a config to update an existing config
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 # This is a comment!
@@ -526,14 +466,12 @@ metrics:
 """
                 )
 
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
             # Just make sure the first config was read
-            self.assertEqual(len(pgmon.Context.config["metrics"]), 2)
+            self.assertEqual(len(pgmon.config["metrics"]), 2)
 
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 # This is a comment!
@@ -546,23 +484,18 @@ metrics:
 """
                 )
 
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
-        self.assertEqual(pgmon.Context.config["min_pool_size"], 7)
-        self.assertEqual(pgmon.Context.config["metrics"]["test1"]["query"][0], "NEW1")
-        self.assertEqual(len(pgmon.Context.config["metrics"]), 1)
+        self.assertEqual(pgmon.config["min_pool_size"], 7)
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "NEW1")
+        self.assertEqual(len(pgmon.config["metrics"]), 1)
 
     def test_read_config__query_file(self):
-        """
-        Test reading a query definition from a separate file
-        """
-        pgmon.Context.config = {}
+        pgmon.config = {}
 
         # Read a config file that reads a query from a file
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 metrics:
@@ -573,30 +506,22 @@ metrics:
 """
                 )
 
-            with open(
-                os.path.join(tmpdirname, "some_query.sql"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/some_query.sql", "w") as f:
                 f.write("This is a query")
 
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
         self.assertEqual(
-            pgmon.Context.config["metrics"]["test1"]["query"][0], "This is a query"
+            pgmon.config["metrics"]["test1"]["query"][0], "This is a query"
         )
 
-    def init_invalid_config_test(self):
-        """
-        Initialize an invalid config read test.  Basically just set up a simple valid config in
-        order to confirm that an invalid read does not modify the live config.
-        """
-        pgmon.Context.config = {}
+    def test_read_config__invalid(self):
+        pgmon.config = {}
 
         # For all of these tests, we start with a valid config and also ensure that
         #  it is not modified when a new config read fails
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 metrics:
@@ -607,48 +532,20 @@ metrics:
 """
                 )
 
-            pgmon.read_config(os.path.join(tmpdirname, "config.yml"))
+            pgmon.read_config(f"{tmpdirname}/config.yml")
 
         # Just make sure the config was read
-        self.assertEqual(pgmon.Context.config["metrics"]["test1"]["query"][0], "TEST1")
-
-    def verify_invalid_config_test(self):
-        """
-        Verify that an invalid read did not modify the live config.
-        """
-        self.assertEqual(pgmon.Context.config["dbuser"], "postgres")
-        self.assertEqual(pgmon.Context.config["metrics"]["test1"]["query"][0], "TEST1")
-
-    def test_read_config__missing(self):
-        """
-        Test reading a nonexistant config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test reading a nonexistant config file
         with tempfile.TemporaryDirectory() as tmpdirname:
             self.assertRaises(
-                FileNotFoundError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "missing.yml"),
+                FileNotFoundError, pgmon.read_config, f"{tmpdirname}/missing.yml"
             )
 
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__invalid(self):
-        """
-        Test reading an invalid config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
-
         # Test reading an invalid config file
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """[default]
 This looks a lot like an ini file to me
@@ -657,26 +554,12 @@ Or maybe a TOML?
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
 
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__invalid_include(self):
-        """
-        Test reading an invalid config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
-
         # Test reading a config that includes an invalid file
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -690,26 +573,14 @@ include:
 """
                 )
             self.assertRaises(
-                FileNotFoundError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                FileNotFoundError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__invalid_log_level(self):
-        """
-        Test reading an invalid log level from a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test invalid log level
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 log_level: noisy
@@ -722,26 +593,14 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__invalid_type(self):
-        """
-        Test reading an invalid query result type form a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test invalid query return type
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -753,57 +612,32 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__invalid_query_dict(self):
-        """
-        Test reading an invalid query definition structure type form a config file.  In other words
-        what's supposed to be a dictionary of the form version => query, we give it something else.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test invalid query dict type
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
 metrics:
   test1:
-    type: row
+    type: lots_of_data
     query: EVIL1
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__missing_type(self):
-        """
-        Test reading a metric with a missing result type from a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test incomplete metric: missing type
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -814,26 +648,14 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__missing_queries(self):
-        """
-        Test reading a metric with no queries from a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test incomplete metric: missing queries
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -843,26 +665,14 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__empty_query_dict(self):
-        """
-        Test reading a fetric with an empty query dict from a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test incomplete metric: empty queries
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -873,26 +683,14 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__none_query_dict(self):
-        """
-        Test reading a metric where the query dict is None from a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test incomplete metric: query dict is None
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -903,53 +701,28 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__missing_metrics(self):
-        """
-        Test reading a config file with no metrics.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test reading a config with no metrics
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__missing_query_file(self):
-        """
-        Test reading a metric from a config file where the query definition cones from a missing
-        file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test reading a query defined in a file but the file is missing
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -961,26 +734,14 @@ metrics:
 """
                 )
             self.assertRaises(
-                FileNotFoundError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                FileNotFoundError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    def test_read_config__invalid_version(self):
-        """
-        Test reading a metric with an invalid PostgreSQL version from a config file.
-        """
-        # Set up the test
-        self.init_invalid_config_test()
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
         # Test invalid query versions
         with tempfile.TemporaryDirectory() as tmpdirname:
-            with open(
-                os.path.join(tmpdirname, "config.yml"), "w", encoding="utf-8"
-            ) as f:
+            with open(f"{tmpdirname}/config.yml", "w") as f:
                 f.write(
                     """---
 dbuser: evil
@@ -992,84 +753,47 @@ metrics:
 """
                 )
             self.assertRaises(
-                pgmon.ConfigError,
-                pgmon.read_config,
-                os.path.join(tmpdirname, "config.yml"),
+                pgmon.ConfigError, pgmon.read_config, f"{tmpdirname}/config.yml"
             )
-
-        # Confirm nothing changed
-        self.verify_invalid_config_test()
-
-    ##
-    # version_num
-    ##
+        self.assertEqual(pgmon.config["dbuser"], "postgres")
+        self.assertEqual(pgmon.config["metrics"]["test1"]["query"][0], "TEST1")
 
     def test_version_num_to_release__valid(self):
-        """
-        Test converting PostgreSQL versions before and after 10 when the numbering scheme changed.
-        """
         self.assertEqual(pgmon.version_num_to_release(90602), 9.6)
         self.assertEqual(pgmon.version_num_to_release(130002), 13)
 
-    ##
-    # parse_version_rss
-    ##
+    def test_parse_version_rss__simple(self):
+        pgmon.parse_version_rss(versions_rss, 13)
+        self.assertEqual(pgmon.latest_version, 130021)
+        self.assertTrue(pgmon.release_supported)
 
-    def test_parse_version_rss__supported(self):
-        """
-        Test parsing a supported version from the RSS feed
-        """
-        pgmon.parse_version_rss(VERSIONS_RSS, 13)
-        self.assertEqual(pgmon.Context.latest_version, 130021)
-        self.assertTrue(pgmon.Context.release_supported)
-
-    def test_parse_version_rss__unsupported(self):
-        """
-        Test parsing an unsupported version from the RSS feed
-        """
-        pgmon.parse_version_rss(VERSIONS_RSS, 9.6)
-        self.assertEqual(pgmon.Context.latest_version, 90624)
-        self.assertFalse(pgmon.Context.release_supported)
+        pgmon.parse_version_rss(versions_rss, 9.6)
+        self.assertEqual(pgmon.latest_version, 90624)
+        self.assertFalse(pgmon.release_supported)
 
     def test_parse_version_rss__missing(self):
-        """
-        Test asking about versions that don't exist in the RSS feed
-        """
+        # Test asking about versions that don't exist
         self.assertRaises(
-            pgmon.LatestVersionCheckError, pgmon.parse_version_rss, VERSIONS_RSS, 9.7
+            pgmon.LatestVersionCheckError, pgmon.parse_version_rss, versions_rss, 9.7
         )
 
         self.assertRaises(
-            pgmon.LatestVersionCheckError, pgmon.parse_version_rss, VERSIONS_RSS, 99
+            pgmon.LatestVersionCheckError, pgmon.parse_version_rss, versions_rss, 99
         )
 
-    ##
-    # get_latest_version
-    ##
-
     def test_get_latest_version(self):
-        """
-        Test getting the latest version from the actual RSS feed
-        """
         # Define a cluster version here so the test doesn't need a database
-        pgmon.Context.cluster_version_next_check = datetime.now() + timedelta(hours=1)
-        pgmon.Context.cluster_version = 90623
+        pgmon.cluster_version_next_check = datetime.now() + timedelta(hours=1)
+        pgmon.cluster_version = 90623
 
         # Set up a default config
-        pgmon.update_deep(pgmon.Context.config, pgmon.DEFAULT_CONFIG)
+        pgmon.update_deep(pgmon.config, pgmon.default_config)
 
         # Make sure we can pull the RSS file (we assume the 9.6 series won't be getting
         # any more updates)
         self.assertEqual(pgmon.get_latest_version(), 90624)
 
-    ##
-    # json_encode_special
-    ##
-
     def test_json_encode_special(self):
-        """
-        Test encoding Decimal types as JSON
-        """
         # Confirm that we're getting the right type
         self.assertFalse(isinstance(Decimal("0.5"), float))
         self.assertTrue(isinstance(pgmon.json_encode_special(Decimal("0.5")), float))