Read Path Dasboards V1

[arodrime]

Add the "Read Path Dashboard" as defined in #27.

To be reviewed / tested and merged!

[tjake]

@tjake, Do you know why we would have mcac_table_key_cache_hit_rate available, but not mcac_table_row_cache_hit_rate or mcac_table_counter_cache_hit_rate?

I'm guessing these only show up when you enable them in cassandra.yaml

[arodrime]

So after looking at MBeans available through jconsole, I can see that there is some inconsistencies for caches at table level:

Also the counter cache is not present at all there (nor chunk cache - but on this one I'm not sure if the table level is really relevant).

@tjake do you think it's relevant to report this inconsistence at the project level?

Other than that, I can use those metrics - at the node level:

Also, at the OS level (collectd), I'm looking for those options (that were available on dashboards we did for Datadog - and are available there out of the box). But I'll look a bit more I did not take the time to do that search seriously yet. Just if you know about it, I'd like to know :).

• Disk Read Latency (io.r_await?)
• Disk Read Queued (io.rrqm/s)
• Disk Utilization (io.util%)