Reduce blocking main thread during span logic

[theguacamoleking]

Problem Statement

Hi there, I wanted to flag an issue where my deeper GraphQL queries take exponentially longer when using Sentry. This looks to be because Sentry logic ends up blocking the main thread

As you can see above, logic within @sentry/opentelemetry is taking up more than 50% of time on the main thread over the period of over 15s. With Sentry disabled, the same GraphQL request takes about 2 seconds.

Solution Brainstorm

System clock lookups

The following code is the worst offender

function shouldCleanupSpan(span, maxStartTimeOffsetSeconds) {
  const cutoff = Date.now() / 1000 - maxStartTimeOffsetSeconds;
  return core.spanTimeInputToSeconds(span.startTime) < cutoff;
}

Specifically the cutoff assignment. I'd propose something like the following where there is only one system clock read for each call of _cleanupOldSpans.

   _cleanupOldSpans(spans = this._finishedSpans) {
    // Get current time (once)
    const currentEpoch = Math.floor(Date.now() / 1000);

    this._finishedSpans = spans.filter(span => {
      const shouldDrop = core.spanTimeInputToSeconds(span.startTime) < currentEpoch - this._timeout);
      DEBUG_BUILD &&
        shouldDrop &&
        utils.logger.log(
          `SpanExporter dropping span ${span.name} (${
            span.spanContext().spanId
          }) because it is pending for more than 5 minutes.`,
        );
      return !shouldDrop;
    });
  }

[s1gr1d]

Hello thanks for raising this and also digging into this problem! I think your proposed change looks reasonable. It's not needed to get a fresh timestamp on every filter. Are you interested in submitting a PR?

[AbhiPrasad]

Opened a PR for this! #14094

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #14094, which was included in the 8.36.0 release.

[AbhiPrasad]

Hi @theguacamoleking could you try the latest release of the JS SDK to see if the profiles look better? We've made some fixes since then.

[getsantry]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀