perf: Send engine callback before tracker bookkeeping and add tracing spans#11970
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anthonyshew merged 3 commits intomainfrom Feb 23, 2026
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perf: Send engine callback before tracker bookkeeping and add tracing spans#11970anthonyshew merged 3 commits intomainfrom
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Adds visit_recv_wait, task_cache_new, and exec_context_new spans to measure where the dispatch loop spends time. Profiling shows 344ms/830ms is idle wait on the engine channel — the bottleneck is cache restore speed, not dispatch overhead.
Instruments micro_frontends_from_disk, task_access_setup, turbo_json_loader_setup, root_turbo_json_load, and pkg_dep_graph_validate to measure the sequential critical path between package graph construction and task execution.
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Move the callback.send() in execute() to fire immediately after output_client.finish(), before the tracker.cached()/build_succeeded bookkeeping. This unblocks the engine's DAG walk sooner — dependents can be dispatched while the completed task's summary tracking runs in the background. Output ordering is preserved because the callback fires after all output is flushed, not before.
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## Release v2.8.11-canary.26 Versioned docs: https://v2-8-11-canary-26.turborepo.dev ### Changes - release(turborepo): 2.8.11-canary.25 (#11971) (`75406f6`) - perf: Send engine callback before tracker bookkeeping and add tracing spans (#11970) (`4b5410b`) --------- Co-authored-by: Turbobot <turbobot@vercel.com>
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Summary
Moves the engine callback send in task
execute()to fire immediately after output is flushed (output_client.finish()), before the tracker bookkeeping (tracker.cached(),tracker.build_succeeded(), etc.). This unblocks the engine's DAG walker sooner — dependent tasks can be dispatched while the completed task's run summary tracking happens in the background.Profiled with
--profileacross three monorepos of varying size (full cache hit scenario, median of 5 warm runs).Changes
Also adds tracing spans throughout the dispatch loop and builder startup for profiling visibility:
visit_recv_wait,task_cache_new,exec_context_newin the dispatch loopmicro_frontends_from_disk,task_access_setup,turbo_json_loader_setup,root_turbo_json_load,pkg_dep_graph_validatein builder startupOutput ordering is preserved because the callback fires after all log replay and output flushing is complete.
crates/turborepo-task-executor/src/exec.rs— Restructuredexecute()to send callback immediately after output flush, before tracker bookkeeping.crates/turborepo-lib/src/task_graph/visitor/mod.rs— Addedvisit_recv_wait,task_cache_new,exec_context_newtracing spans.crates/turborepo-lib/src/run/builder.rs— Added tracing spans for uninstrumented startup phases.