Fix log streaming missing frames

[arkadiuss]

Hi,

this MR aims to address the issue reported here #11653 . I described the problem in this comment.

This solution adds one more channel to the streamFile function that instead of cancelling on the event from channel when eof is reached, it performs one more read until eof which I think should be an expected behavior while streaming logs.

It is a draft for now opened for discussion. I confirmed that it works for the example posted in the issue. It should work since while newFileEvent is generated, the previous file is already full.

I haven't checked tests yet.

[hashicorp-cla]

All committers have signed the CLA.

[tgross]

Hi @arkadiuss and thanks for this PR! I see where you're going with this but I've left some remarks about the previous channel that we got from blockUntilNextLog and what we're doing with it.

[arkadiuss]

I wanted to cover this scenario in tests. It was hard to create deterministic test since we don't know which event will come first, but I modfied the existing test in a way that the old code (without fix) fails it in most of the cases.

[tgross]

@arkadiuss if you'd like to add a changelog bugfix entry that'd be appreciated. Create a file at .changelog/11721.txt that looks something like this. With language something like:

client: Fixed a bug where the allocation log streaming API was missing log lines that spanned log file rotation

[arkadiuss]

@arkadiuss if you'd like to add a changelog bugfix entry that'd be appreciated. Create a file at .changelog/11721.txt that looks something like this. With language something like:

client: Fixed a bug where the allocation log streaming API was missing log lines that spanned log file rotation

Thanks, it's added

[tgross]

LGTM! Thanks for the PR @arkadiuss and thanks for sticking with it through a tricky review! This will ship in the next scheduled release of Nomad.

[arkadiuss]

LGTM! Thanks for the PR @arkadiuss and thanks for sticking with it through a tricky review! This will ship in the next scheduled release of Nomad.

Awesome! It was great experience to work with you on it. Thank you for this, in-depth questions and quick responses!

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