/**
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* The `trace_events` module provides a mechanism to centralize tracing information
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* generated by V8, Node.js core, and userspace code.
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*
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* Tracing can be enabled with the `--trace-event-categories` command-line flag
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* or by using the `trace_events` module. The `--trace-event-categories` flag
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* accepts a list of comma-separated category names.
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*
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* The available categories are:
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*
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* * `node`: An empty placeholder.
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* * `node.async_hooks`: Enables capture of detailed `async_hooks` trace data.
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* The `async_hooks` events have a unique `asyncId` and a special `triggerId` `triggerAsyncId` property.
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* * `node.bootstrap`: Enables capture of Node.js bootstrap milestones.
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* * `node.console`: Enables capture of `console.time()` and `console.count()`output.
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* * `node.dns.native`: Enables capture of trace data for DNS queries.
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* * `node.environment`: Enables capture of Node.js Environment milestones.
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* * `node.fs.sync`: Enables capture of trace data for file system sync methods.
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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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* * `node.promises.rejections`: Enables capture of trace data tracking the number
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* of unhandled Promise rejections and handled-after-rejections.
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* * `node.vm.script`: Enables capture of trace data for the `vm` module's`runInNewContext()`, `runInContext()`, and `runInThisContext()` methods.
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* * `v8`: The `V8` events are GC, compiling, and execution related.
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*
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* By default the `node`, `node.async_hooks`, and `v8` categories are enabled.
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*
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* ```bash
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* node --trace-event-categories v8,node,node.async_hooks server.js
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* ```
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*
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* Prior versions of Node.js required the use of the `--trace-events-enabled`flag to enable trace events. This requirement has been removed. However, the`--trace-events-enabled` flag _may_ still be
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* used and will enable the`node`, `node.async_hooks`, and `v8` trace event categories by default.
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*
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* ```bash
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* node --trace-events-enabled
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*
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* # is equivalent to
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*
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* node --trace-event-categories v8,node,node.async_hooks
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* ```
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*
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* Alternatively, trace events may be enabled using the `trace_events` module:
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*
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* ```js
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* const trace_events = require('trace_events');
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* const tracing = trace_events.createTracing({ categories: ['node.perf'] });
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* tracing.enable(); // Enable trace event capture for the 'node.perf' category
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*
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* // do work
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*
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* tracing.disable(); // Disable trace event capture for the 'node.perf' category
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* ```
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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) tab of Chrome.
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*
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* The logging file is by default called `node_trace.${rotation}.log`, where`${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}`:
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*
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* ```bash
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* node --trace-event-categories v8 --trace-event-file-pattern '${pid}-${rotation}.log' server.js
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* ```
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*
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* 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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*
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* The features from this module are not available in `Worker` threads.
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* @experimental
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* @see [source](https://github.com/nodejs/node/blob/v17.0.0/lib/trace_events.js)
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*/
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declare module 'trace_events' {
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/**
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* The `Tracing` object is used to enable or disable tracing for sets of
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* categories. Instances are created using the
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* `trace_events.createTracing()` method.
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*
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* When created, the `Tracing` object is disabled. Calling the
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* `tracing.enable()` method adds the categories to the set of enabled trace
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* event categories. Calling `tracing.disable()` will remove the categories
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* from the set of enabled trace event categories.
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*/
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interface Tracing {
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/**
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* A comma-separated list of the trace event categories covered by this
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* `Tracing` object.
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*/
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readonly categories: string;
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/**
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* Disables this `Tracing` object.
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*
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* Only trace event categories _not_ covered by other enabled `Tracing`
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* objects and _not_ specified by the `--trace-event-categories` flag
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* will be disabled.
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*/
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disable(): void;
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/**
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* Enables this `Tracing` object for the set of categories covered by
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* the `Tracing` object.
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*/
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enable(): void;
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/**
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* `true` only if the `Tracing` object has been enabled.
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*/
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readonly enabled: boolean;
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}
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interface CreateTracingOptions {
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/**
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* An array of trace category names. Values included in the array are
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* coerced to a string when possible. An error will be thrown if the
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* value cannot be coerced.
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*/
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categories: string[];
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}
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/**
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* Creates and returns a `Tracing` object for the given set of `categories`.
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*
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* ```js
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* const trace_events = require('trace_events');
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* const categories = ['node.perf', 'node.async_hooks'];
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* const tracing = trace_events.createTracing({ categories });
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* tracing.enable();
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* // do stuff
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* tracing.disable();
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* ```
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* @since v10.0.0
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* @return .
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*/
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function createTracing(options: CreateTracingOptions): Tracing;
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/**
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* Returns a comma-separated list of all currently-enabled trace event
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* categories. The current set of enabled trace event categories is determined
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* by the _union_ of all currently-enabled `Tracing` objects and any categories
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* enabled using the `--trace-event-categories` flag.
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*
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* Given the file `test.js` below, the command`node --trace-event-categories node.perf test.js` will print`'node.async_hooks,node.perf'` to the console.
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*
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* ```js
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* const trace_events = require('trace_events');
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* const t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });
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* const t2 = trace_events.createTracing({ categories: ['node.perf'] });
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* const t3 = trace_events.createTracing({ categories: ['v8'] });
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*
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* t1.enable();
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* t2.enable();
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*
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* console.log(trace_events.getEnabledCategories());
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* ```
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* @since v10.0.0
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*/
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function getEnabledCategories(): string | undefined;
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}
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declare module 'node:trace_events' {
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export * from 'trace_events';
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}
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