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PR-URL: https://github.com/nodejs/node/pull/19056 Reviewed-By: Matheus Marchini <matheus@sthima.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
51 lines
1.8 KiB
Markdown
51 lines
1.8 KiB
Markdown
# Tracing
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<!--introduced_in=v7.7.0-->
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Trace Event provides a mechanism to centralize tracing information generated by
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V8, Node.js core, and userspace code.
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Tracing can be enabled by passing the `--trace-events-enabled` flag when
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starting a Node.js application.
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The set of categories for which traces are recorded can be specified using the
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`--trace-event-categories` flag followed by a list of comma separated category
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names.
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The available categories are:
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* `node`
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* `node.async_hooks` - Enables capture of detailed async_hooks trace data.
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* `node.perf` - Enables capture of [Performance API] measurements.
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* `node.perf.usertiming` - Enables capture of only Performance API User Timing
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measures and marks.
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* `node.perf.timerify` - Enables capture of only Performance API timerify
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measurements.
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* `v8`
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By default the `node`, `node.async_hooks`, and `v8` categories are enabled.
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```txt
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node --trace-events-enabled --trace-event-categories v8,node,node.async_hooks server.js
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```
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Running Node.js with tracing enabled will produce log files that can be opened
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in the [`chrome://tracing`](https://www.chromium.org/developers/how-tos/trace-event-profiling-tool)
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tab of Chrome.
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The logging file is by default called `node_trace.${rotation}.log`, where
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`${rotation}` is an incrementing log-rotation id. The filepath pattern can
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be specified with `--trace-event-file-pattern` that accepts a template
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string that supports `${rotation}` and `${pid}`. For example:
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```txt
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node --trace-events-enabled --trace-event-file-pattern '${pid}-${rotation}.log' server.js
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```
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Starting with Node.js 10.0.0, the tracing system uses the same time source
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as the one used by `process.hrtime()`
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however the trace-event timestamps are expressed in microseconds,
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unlike `process.hrtime()` which returns nanoseconds.
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[Performance API]: perf_hooks.html
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