Google-cloud-go: pubsub: mimic queue error in pstest

[alicebob]

pstest is great for testing pubsub, makes using queues so much easier.

Could there be an option to simulate a Queue() failure? Maybe something along the lines of:

srv := pstest.NewServer()
...
srv.NextQueueError(errors.New("oops"))

It could either return an error only for the next call to Queue(), or for every call after this.

[hongalex]

Hi, thanks for opening this feature request. Could you elaborate further on the Queue feature you would like to implement? I might be missing something, but I'm not sure exactly how it relates to testing pubsub. Thanks!

[alicebob]

Hi @hongalex.

sorry, I misnamed the method call. Let me explain.

In normal pubsub usage you do a:

res := topic.Publish(ctx, &pubsub.Message{Data: []byte("payload")})

res is a PublishResult, which you then call res.Get() on to get the result.

Usually the Publish() will be fine, but it's not impossible it fails. Then the res.Get() will return an error, and I have to deal with it.

Currently I can test the topic.Publish() very nicely with pstest, but there is no way to have res.Get() return an error, so I can't test that code path.

[hongalex]

Thanks for the clarification. Yeah this seems like a potentially useful feature, though I'm currently prioritizing other items so I won't be able to get to adding this right away. Alternatively, if you're willing to take a look at our CONTRIBUTING.md and feel like adding this feature, I'd be happy to review it for you.

In any case, leaving this issue open until the feature is added.

[hongalex]

This is now available as part of pubsub v.1.7.0 with the Reactor options. Specifically, passing in WithErrorInjection into pstest server instantiation will get you what you want. This isn't a queue, but will call your reactor function for every function for a specific RPC. For more info see here.

[alicebob]

:confetti_ball:
Thanks for adding this!

[hongalex]

You're welcome! To avoid confusion, we recommend using pubsub/v1.8.0 or higher. Unfortunately, we had to make a breaking change between 1.7.0 -> 1.8.0 (specifically WithErrorInjection now takes in an additional grpc Code argument instead of just a message string). In addition, ErrorInjectionReactor is no longer exported.

In any case, if look at the types in https://pkg.go.dev/cloud.google.com/go/[email protected]/pstest, that shows you the types you should be able to use.