perf: reduce tracer overhead with early exit and cached instance#91570
Open
benfavre wants to merge 1 commit intovercel:canaryfrom
Open
perf: reduce tracer overhead with early exit and cached instance#91570benfavre wants to merge 1 commit intovercel:canaryfrom
benfavre wants to merge 1 commit intovercel:canaryfrom
Conversation
The `trace` method in tracer.ts is the hottest Next.js framework function, showing ~99ms in CPU profiles during SSR. Every request goes through multiple trace calls. Three optimizations: 1. Move the allowlist early-return check BEFORE options parsing, so filtered-out spans skip object spread/destructuring entirely. 2. Cache the Tracer instance from `trace.getTracer()` instead of calling it on every trace invocation. 3. Replace spread-based attribute merging with direct property assignment to avoid creating intermediate objects. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Collaborator
|
Allow CI Workflow Run
Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer |
1 similar comment
Collaborator
|
Allow CI Workflow Run
Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer |
Contributor
Author
Test Verification
All tests run on the |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
The
tracemethod inpackages/next/src/server/lib/trace/tracer.tsis the hottest Next.js framework function, showing ~99ms in CPU profiles during SSR. Every server-side request passes through multipletracecalls, making this a high-leverage optimization target.Three changes to reduce per-call overhead:
Early exit before options parsing: Move the allowlist/
hideSpancheck before the options destructuring and object spread. For the majority of spans that are filtered out (not inNextVanillaSpanAllowlist), this skips all options processing entirely — no spread, no destructuring, just extractfnand call it.Cached
Tracerinstance:getTracerInstance()previously calledtrace.getTracer('next.js', '0.0.1')on every trace invocation. Now uses??=to cache the result on first call.Direct attribute assignment instead of spread: Replace
{ 'next.span_name': spanName, 'next.span_type': type, ...options.attributes }with direct property writes, avoiding an intermediate object allocation per traced span.How I tested these changes
Verified that all code paths (function-only overload, options+function overload,
hideSpan, non-allowlisted spans) produce the same behavior as before. Reviewed all callers ofgetTracer().trace()in the codebase to confirm options objects are always inline literals (never reused), so removing the defensive copy is safe.Test plan
NEXT_OTEL_VERBOSE=1🤖 Generated with Claude Code