Client Time Histogram for bidi_stream

[Dave Johnston]

It looks like after adding EnableClientHandlingTimeHistogram() I can collect counters for unary rpc messages, but there is not reporting on bidirectional streams.

Is this intentional, or a bug?

[Frederic Branczyk]

A bi-directional stream should by definition always be long lasting, what would the histogram reflect?

[Dave Johnston]

I was hoping to be able to use it to calculate the average number of messages sent over the stream per second, over a period of time.

[Frederic Branczyk]

I think that's reasonable, but that would be accomplished with a counter, as you use the rate function over the monotonically increasing counter value, thus yielding the messages per second. This is already available with these metrics:

go-grpc-prometheus/client_metrics.go

Lines 44 to 54 in c225b8c

 clientStreamMsgReceived: prom.NewCounterVec( 
 	opts.apply(prom.CounterOpts{ 
 		Name: "grpc_client_msg_received_total", 
 		Help: "Total number of RPC stream messages received by the client.", 
 	}), []string{"grpc_type", "grpc_service", "grpc_method"}), 
  
 clientStreamMsgSent: prom.NewCounterVec( 
 	opts.apply(prom.CounterOpts{ 
 		Name: "grpc_client_msg_sent_total", 
 		Help: "Total number of gRPC stream messages sent by the client.", 
 	}), []string{"grpc_type", "grpc_service", "grpc_method"}), 

[Dave Johnston]

Thanks - looks like the irate() function with the above counter solves my issue.