JavaClient can stream the HTTP response body

[alex-james-dev]

Make java_http stream the HTTP response body one byte at a time. Currently, java_http
gets all the bytes of the HTTP response body and then creates a stream from these bytes.

• Use Isolate.spawn instead of Isolate.run so that we can send more than one message from the worker isolate.

• Make the worker isolate send the HTTP response status code, reason phrase and response headers (in that order) to the main isolate.

• The rest of the messages from the worker isolate are the HTTP response body bytes. Create the response body stream from these bytes.

• Handle the worker isolate sending ClientException as well as the HTTP response data.

• Close the worker isolate if there is a ClientException when getting the HTTP response status code.

• Make java_http pass testResponseBodyStreamed in package:http_client_conformance_tests.

Relevant tracking issue: #957.

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[brianquinlan]

Is this ready for review?

[alex-james-dev]

Is this ready for review?

Hey @brianquinlan,

There are a couple of ClientExceptions still being thrown inside the worker isolate. But I'm happy to get this PR reviewed/merged and make the extra changes in a separate PR.

In particular:

• There are some unhandled exceptions occurring inside the worker isolate due to calls to _parseContentLengthHeader(): unhandled exception. I think the tests are still passing because we call _parseContentLengthHeader() in both the main isolate and the worker isolate.

• We throw a ClientException inside the worker isolate when there is an issue retrieving the status code. I can change it so that the ClientException is sent over the SendPort instead. I don't think we have a test for this yet. I've created a basic test locally to check that the ClientException is being thrown inside the worker isolate.

Thank you!

[brianquinlan]

Won't it exit on it's own?

[alex-james-dev]

Hey @brianquinlan,

I think it does exit on its own normally although I'm not 100% sure about when the user cancels the StreamSubscription of the StreamedResponse.stream. But perhaps we don't have to worry too much about this?

[natebosch]

Can you edit the 1st message in the PR to be a description of the code changes that we can use as the commit message?
See https://google.github.io/eng-practices/review/developer/cl-descriptions.html#informative for more on authoring commit messages ("cl descriptions" in the link).

[alex-james-dev]

Hey @natebosch,

I've updated the 1st message in the PR. Thanks for the link, it was very helpful and I've bookmarked it for future reference 🔖.

Thank you!