Been reading the following https://medium.com/dbkoda/the-notorious-database-cache-hit-ratio-c7d432381229 article which seems to calculate WiredTiger cache miss rate from data taken in db.serverStatus() output.
However, after performing the command (and also checking that the Java API doesn't have such method, don't really know how he is using the API?), just by checking what the method shows I can't really see the properties from the Document he is trying to retrieve, which are basically 'pages requested from the cache' and 'pages read into cache'.
The only metrics I can see related to that are a couple included within extra_fields, which are page_faults and page_reclaims, and if I'm correct those are both cache misses and cache hits respectively, right?
I'm trying to obtain cache performance (if it's hitting the cache or not after performing certain aggregations) when using certain queries.
Is there any way to obtain this metric straight away via MongoDB commands?
The code given is intended to be run in
mongoshell.The driver equivalent is the https://docs.mongodb.com/manual/reference/command/serverStatus/ command.
You would execute it using your driver's facility to run admin commands or arbitrary commands or database commands. For Ruby driver, this is https://docs.mongodb.com/ruby-driver/current/tutorials/ruby-driver-database-tasks/#arbitrary-comands.