Add script to shot tempalte coverage

* Add a script to compare the defined metrics with those used in the
  Zabbix template.

* Add a Makefile target to run the above script.

Makefile

@@ -110,6 +110,11 @@ endif
 query-tests:
 	cd tests ; ./run-tests.sh
 
+# Compare the sample metrics with the Zabbix template
+template-coverage:
+	$(PYTHON) zabbix_templates/coverage.py sample-config/pgmon-metrics.yml zabbix_templates/pgmon_templates.yaml
+
+
 # Install the script at the specified base directory (common components)
 install-common:
 	# Set up directories

zabbix_templates/coverage.py

@@ -0,0 +1,129 @@
+#!/usr/bin/env python3
+
+# Compare the items defined in a Zabbix template with the metrics defined in a config file.
+
+import sys
+
+import yaml
+
+# Special built in metrics
+SPECIAL = {
+    "agent_version",
+    "latest_version_info"
+}
+
+
+class NonMetricItemError(Exception):
+    """
+    A given item does not directly use a metric
+    """
+
+
+def read_metrics(file):
+    """
+    Read the metrics from a config file and return the list of names
+
+    params:
+        file: the name of the file to read
+
+    returns:
+        list of metric named defined in the file
+
+    raises:
+        yaml.parser.ParserError: invalid yaml file
+    """
+    names = set()
+    config = None
+
+    with open(file, "r", encoding="utf-8") as f:
+        config = yaml.safe_load(f)
+
+    try:
+        for m in config["metrics"].keys():
+            names.add(m)
+    except KeyError:
+        pass
+
+    return names
+
+
+def extract_metric(item):
+    """
+    Extract the metric from an item definition
+
+    params:
+        item: the item/discovery/prototype definition dict
+
+    returns:
+        the name of the metric used in the item
+
+    raises:
+        NonMetricItemError: the item does not directly use a metric
+    """
+    try:
+        if item["type"] == "HTTP_AGENT":
+            url = item["url"]
+            if url.startswith("http://localhost:{$AGENT_PORT}"):
+                return url.split("/")[-1]
+    except KeyError:
+        raise NonMetricItemError()
+
+    raise NonMetricItemError()
+
+
+def read_template(file):
+    """
+    Read the items from a Zabbix template and return the list of metric names
+
+    params:
+        file: the name of the file to read
+
+    returns:
+        list of metric named used in the file
+
+    raises:
+        yaml.parser.ParserError: invalid yaml file
+    """
+    names = set()
+    config = None
+
+    with open(file, "r", encoding="utf-8") as f:
+        config = yaml.safe_load(f)
+
+    try:
+        for template in config["zabbix_export"]["templates"]:
+            for item in template["items"]:
+                try:
+                    names.add(extract_metric(item))
+                except NonMetricItemError:
+                    pass
+
+            for rule in template["discovery_rules"]:
+                try:
+                    names.add(extract_metric(rule))
+                except NonMetricItemError:
+                    pass
+
+                for proto in rule["item_prototypes"]:
+                    try:
+                        names.add(extract_metric(proto))
+                    except NonMetricItemError:
+                        pass
+    except KeyError:
+        pass
+
+    return names
+
+
+if __name__ == '__main__':
+    config_file = sys.argv[1]
+    config_metrics = read_metrics(config_file)
+
+    template_file = sys.argv[2]
+    template_metrics = read_template(template_file) - SPECIAL
+
+    config_only = config_metrics - template_metrics
+    template_only = template_metrics - config_metrics
+
+    print("Config only: {}".format(sorted(list(config_only))))
+    print("Template only: {}".format(sorted(list(template_only))))