CASSANDRA-15582 involves quality around metrics and it was mentioned that reviewing and improving documentation around metrics would fall into that scope. Please consider some of this analysis in determining what improvements to make here:
Please see this spreadsheet that itemizes almost all of cassandra's metrics and whether they are documented or not (and other notes). That spreadsheet is "almost all" because there are some metrics that don't seem to initialize as part of Cassandra startup (i was able to trigger some to initialize, but all were not immediately obvious). The missing metrics seem to be related to the following:
- ThreadPool metrics - only some initialize at startup the list of which follow below
- Streaming Metrics
- HintedHandoff Metrics
- HintsService Metrics
Here are the ThreadPool scopes that get listed:
I noticed that Keyspace Metrics have this note: "Most of these metrics are the same as the Table Metrics above, only they are aggregated at the Keyspace level." I think I've isolated those metrics on table that are not on keyspace to specifically be:
Someone with greater knowledge of this area might consider it worth the effort to see if any of these metrics should be aggregated to the keyspace level in case they were inadvertently missed. In any case, perhaps the documentation could easily now reflect which metric names could be expected on Keyspace.
The DroppedMessage metrics have a much larger body of scopes than just what were documented:
I suppose I may yet be missing some metrics as my knowledge of what's available is limited to what I can get from JMX after cassandra initialization (and some initial starting commands) and what's int he documentation. If something is present that is missing from both then I won't know it's there. Anyway, perhaps this issue can help build some discussion around the improvements that might be made given the analysis that has been provided so far.