aa810a3142
We may see RPCs that are dispatched by a client but do not arrive at the server for some time afterwards. To have insight into potential request latency at this layer we want to publish the time delta between when a client sent an RPC and when the server received it. This PR updates the gRPC client interceptor to add the current time to the gRPC request metadata context when it dispatches an RPC. The server side interceptor is updated to pull the client request time out of the gRPC request metadata. Using this timestamp it can calculate the latency and publish it as an observation on a Prometheus histogram. Accomplishing the above required wiring a clock through to each of the client interceptors. This caused a small diff across each of the gRPC aware boulder commands. A small unit test is included in this PR that checks that a latency stat is published to the histogram after an RPC to a test ChillerServer is made. It's difficult to do more in-depth testing because using fake clocks makes the latency 0 and using real clocks requires finding a way to queue/delay requests inside of the gRPC mechanisms not exposed to Boulder. Updates https://github.com/letsencrypt/boulder/issues/3635 - Still TODO: Explicitly logging latency in the VA, tracking outstanding RPCs as a gauge. |
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| main_test.go | ||