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diagnostics_channel: early-exit tracing channel trace methods #51915

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merged 1 commit into from
Mar 7, 2024

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@Qard Qard commented Feb 28, 2024

This documents and enforces that tracing channel will not publish events unless subscribers are present at the start of the trace. This enables a more performant early exit and ensures graph completeness as prior to this change a subscription added midway through a trace could receive the later events despite missing the earlier ones.

I'm unsure if we should consider this a major change as there is a behaviour change in that a subscriber will no longer receive events for traces which began before the subscription was made. This could be considered a major change, or it could be considered a bug fix--we'll need to decide how we should frame this.

cc @nodejs/diagnostics

@Qard Qard added doc Issues and PRs related to the documentations. test Issues and PRs related to the tests. diag-agenda Issues and PRs to discuss during the meetings of the diagnostics working group. diagnostics_channel Issues and PRs related to diagnostics channel labels Feb 28, 2024
@nodejs-github-bot nodejs-github-bot added the needs-ci PRs that need a full CI run. label Feb 28, 2024
@Qard Qard force-pushed the tracing-channel-early-return branch 3 times, most recently from 8edb24d to 657f046 Compare February 28, 2024 22:13
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@Qard Qard force-pushed the tracing-channel-early-return branch 3 times, most recently from 38c8af3 to 91cb93b Compare February 28, 2024 23:04
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There seem to be spurious changes to other files. Could you fix?

My 2 cents for this is that the data produced by a tracing channel that's not started at startup is useless because incomplete and it could lead to crashes/unexpected behaviors. A developer can always move the tracing setup at the beginning of the program and capture everything. I think this is a bugfix.

@Qard Qard force-pushed the tracing-channel-early-return branch from 91cb93b to 244ee51 Compare February 29, 2024 19:31
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Qard commented Feb 29, 2024

Apologies for the formatting irregularities. I've been trying out Zed and it apparently likes to auto-format buffers not just when opening them, but also when they appear in search results. 😐


// While subscribe occurs _before_ the promise resolves,
// no async events should be published.
channel.tracePromise(() => {
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Suggested change
channel.tracePromise(() => {
channel.tracePromise(common.mustCall(() => {

You could even add asserts that this/arguments/return values are correctly forwarded.
Similar of the other APIs. But feel free to ignore and keep as is.

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Flarna commented Mar 1, 2024

I interpret this also as a bugfix.
TracingChannel is anyway experimental therefore it's not that important anyway.

@Flarna Flarna added the request-ci Add this label to start a Jenkins CI on a PR. label Mar 1, 2024
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CI: https://ci.nodejs.org/job/node-test-pull-request/57535/

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Clarification of intent for the API is good for me.

@Qard Qard added the commit-queue Add this label to land a pull request using GitHub Actions. label Mar 7, 2024
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@nodejs-github-bot nodejs-github-bot merged commit 4f3cf4e into nodejs:main Mar 7, 2024
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Landed in 4f3cf4e

@Qard Qard deleted the tracing-channel-early-return branch March 7, 2024 17:50
rdw-msft pushed a commit to rdw-msft/node that referenced this pull request Mar 26, 2024
PR-URL: nodejs#51915
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Gerhard Stöbich <[email protected]>
Reviewed-By: Chengzhong Wu <[email protected]>
marco-ippolito pushed a commit that referenced this pull request May 2, 2024
PR-URL: #51915
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Gerhard Stöbich <[email protected]>
Reviewed-By: Chengzhong Wu <[email protected]>
}
}

get hasSubscribers() {
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It looks like there are no tests for this method. Though it does get code coverage since it's used by other methods. Was that intentional? Seems like an accident since it's a public method. Also it looks like there's no documentation?

tlhunter added a commit to tlhunter/node that referenced this pull request May 8, 2024
tlhunter added a commit to tlhunter/node that referenced this pull request May 8, 2024
tlhunter added a commit to tlhunter/node that referenced this pull request May 8, 2024
tlhunter added a commit to tlhunter/node that referenced this pull request May 8, 2024
tlhunter added a commit to tlhunter/node that referenced this pull request May 8, 2024
tlhunter added a commit to DataDog/dc-polyfill that referenced this pull request May 9, 2024
- some `diagnostics_channel` changes landed in Node.js in nodejs/node#51915
  - this PR adds the `TracingChannel#hasSubscribers` helper method available in Node.js v22 and v20.13
  - this PR _does not_ add the early exit functionality from that same commit
- since this PR only implements half of the functionality in that commit we aren't fully v22 and v20.13 compatible
  - for that reason I haven't updated the README to state that we track said versions
  - I did add a note to the README about this partial jump in functionality
- this PR also adds CI tests against Node.js v22.x
- partially obsoletes #10 which is a WIP that attempted to implement both
tlhunter added a commit to tlhunter/node that referenced this pull request May 9, 2024
tlhunter added a commit to tlhunter/node that referenced this pull request May 9, 2024
tlhunter added a commit to tlhunter/node that referenced this pull request May 9, 2024
jcbhmr pushed a commit to jcbhmr/node that referenced this pull request May 15, 2024
PR-URL: nodejs#51915
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Gerhard Stöbich <[email protected]>
Reviewed-By: Chengzhong Wu <[email protected]>
nodejs-github-bot pushed a commit that referenced this pull request Jul 24, 2024
follow up work for #51915

PR-URL: #52908
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: James M Snell <[email protected]>
targos pushed a commit that referenced this pull request Jul 28, 2024
follow up work for #51915

PR-URL: #52908
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: James M Snell <[email protected]>
RafaelGSS pushed a commit that referenced this pull request Aug 5, 2024
follow up work for #51915

PR-URL: #52908
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: James M Snell <[email protected]>
marco-ippolito pushed a commit that referenced this pull request Aug 19, 2024
follow up work for #51915

PR-URL: #52908
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: James M Snell <[email protected]>
marco-ippolito pushed a commit that referenced this pull request Aug 19, 2024
follow up work for #51915

PR-URL: #52908
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: James M Snell <[email protected]>
marco-ippolito pushed a commit that referenced this pull request Aug 19, 2024
follow up work for #51915

PR-URL: #52908
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: James M Snell <[email protected]>
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