Nova Resource:Wdq-mm/Documentation

This project primarily provides https://wdq.wmflabs.org, a WikiData query service.

It is fully puppetized and runs on two machines (wdq-mm-01 and wdq-mm-02), load balanced via a simple round robin mechanism. The load balancer is an nginx proxy that does passive health checks (stops routing to an instance if wdq is not responding), and lives on wdq-mm-01. Each instance also has a local version of monit running, that restarts the local wdq deamon if it is not responding. This fights against the deadlocks that wdq is sometimes prone to (multi-threaded C++ applications are hard).