1.4: RequestLog with streaming results

[benjchristensen]

Now that we support an Observable we can have a stream of results. The RequestLog currently will mark SUCCESS for each onNext rather than the terminal event.

Everything behaves fine for scalar responses, just need to fix it for a use case where the Observables returns more than 1 value.

[mattrjacobs]

The plan here is to add 2 new states to the HystrixRequestLog: EMIT and FALLBACK_EMIT. These represent the construct() and resumeWithFallback() methods invoking onNext().

Some possible new RequestLog strings:
[EMITx10, SUCCESS]
[EMITx3, FAILURE]
[EMITx4, FAILURE, FALLBACK_EMITx3, FALLBACK_SUCCESS]
[EMITx1, FAILURE, FALLBACK_EMITx10, FALLBACK_FAILURE]

[mattrjacobs]

One question which I'm not sure about is if we want these new event types in the RequestLog of a HystrixCommand. It doesn't give any info, as we will always see an onNext/onCompleted pair (EMIT/SUCCESS) together.

But it also feels a little strange to special-case this.

My initial inclination is to only present these events for HystrixObservableCommand, both to preserve the RequestLog as-is for this case, and because it's not especially meaningful

[benjchristensen]

I agree it should not be on the existing HystrixCommand, only ObservableCommand.

[mattrjacobs]

To make this concrete, here are some sample request logs for HystrixObservableCommand. HystrixCommand request logs are unchanged, as described above.

• TestCommandWithMultipleValues[EMITx3, SUCCESS][30ms]
• TestPartialSuccess[EMITx3, FAILURE][39ms]
• TestPartialSuccessWithFallback[EMITx3, FAILURE, FALLBACK_EMITx4, FALLBACK_SUCCESS][39ms]

[mattrjacobs]

Done in #604