Add optional statistics for Redis queries.

[yole]

If config.redis.analyze_performance is enabled, log the
number and types of Redis queries executed on each
request.

[epicmonkey]

Let's discuss, i.e. there are external tools that can gather pretty much the same stats using either INFO or MONITOR redis commands. For example: https://github.com/facebookarchive/redis-faina

[yole]

Do you know of any external tool which can correlate the stats with the URL being requested? It's not interesting for me to simply see how many operations of a certain kind we're performing in total - I need to see the statistics per request, and separately for each kind of request.

[epicmonkey]

Personally, I do not know any other tools other than faina. Though my feelings are it could be extracted from the application to express middleware (./lib folder or whatever).

[epicmonkey]

Ultimately, we must not confuse two things: 1) log/monitor queries (application), and 2) analyze performance on top of it (middleware).

[yole]

If you prefer, I can extract the logic to a more isolated component.

[epicmonkey]

That would be fantastic! BTW, I may be wrong when I said that "performance" is going to be a middleware. Up to you though.