Add metrics for tracking cache hit ratios

src/pgmon.py

@@ -656,7 +656,11 @@ def test_queries():
         # If the metric has arguments to use while testing, grab those
         args = metric.get("test_args", {})
         # Run the query without the ability to retry.
-        res = sample_metric(dbname, name, args, retry=False)
+        try:
+            res = sample_metric(dbname, name, args, retry=False)
+        except MetricVersionError:
+            print("{} -> Unsupported for this version".format(name))
+            continue
         # Compare the result to the provided sample results
         # TODO
         print("{} -> {}".format(name, res))
@@ -714,6 +718,7 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
             except LatestVersionCheckError as e:
                 log.error("Failed to retrieve latest version information: {}".format(e))
                 self._reply(503, "Failed to retrieve latest version info")
+            return
 
         # Note: parse_qs returns the values as a list.  Since we always expect
         #       single values, just grab the first from each.