Streaming HTTP request with Webclient blocks

[hora...@gmail.com]

Hello,

I am attempting to stream a large HTTP request between my Vert.x services. For this purpose, I am using io.vertx.reactivex.ext.web.client.WebClient (created with HttpEndpoint.rxGetWebClient(serviceDiscovery, rec ->rec.getName().equals(serviceName), webClientOptions)), which takes a Flowable as input for the rxSendStream method. 

The Flowable in question is based on a ReplaySubject populated with buffers generated by another method.

However, I have encountered an issue where the other service does not receive all the buffers. Specifically:

1. The HTTP request appears to emit a certain number of buffers and then blocks, leaving the request incomplete.

2. On the consumer side, fewer buffers are received than expected, and the process becomes stuck without completing the request.

I have tested the behavior with Flowable directly (without using ReplaySubject), and the result appears to be the same.

Could this issue be related to how WebClient handles backpressure? Is it possible that the backpressure handling mechanism is causing the request to block?

I am using the following snipets of the code :

```

var subject = ReplaySubject.<Buffer>create(); var flowableStream = subject.toFlowable(BackpressureStrategy.BUFFER);

 ... 

 var request = webClient.put(SERVICE_PATH) .putHeader(CONTENT_TYPE.toString(),APPLICATION_JSON); 

 setOptionalParameters(httpServerRequest, request); return 

request.as(BodyCodec.buffer()) .expect(RESPONSE_CREATED_PREDICATE).rxSendStream(flowableStream).ignoreElement().doOnComplete(() -> LOG.info("executed successfully")); 

 ... 

 subject.onNext(...)

```

thank you for any help

[Thomas SEGISMONT]

Hi,

Would you mind sharing a small reproducer with us please?

Thank you

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[Michael Horák]

sure, here is the reproducer: https://github.com/horak90/webclient_reproducer

Please keep me update on the issue

Thank you,

Michael

st 29. 1. 2025 v 14:46 odesílatel Thomas SEGISMONT <tsegi...@gmail.com> napsal:

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[hora...@gmail.com]

Hello,

could you please provide an update on the issue status? Additionally, if there are any workarounds to stream Flowable, I’d appreciate it, as this is currently blocking me.

Thank you,

Michael

Dne čtvrtek 30. ledna 2025 v 15:02:30 UTC+1 uživatel Michael Horák napsal:

[hora...@gmail.com]

Hello, could you please let me know if there any news on this topic

Thanks

Dne pondělí 10. února 2025 v 9:28:42 UTC+1 uživatel hora...@gmail.com napsal:

[Thomas SEGISMONT]

Hi,

I haven't been able to look at the reproducer. I will look into it today.

Regards,

Thomas

To view this discussion, visit https://groups.google.com/d/msgid/vertx/bc355b94-23dc-43ce-afb1-df4f76113727n%40googlegroups.com.

[Thomas SEGISMONT]

I just noticed this is now tracked by https://github.com/vert-x3/vertx-web/issues/2725

The conversation will continue there