| 1 | /**
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| 2 | * The `trace_events` module provides a mechanism to centralize tracing information
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| 3 | * generated by V8, Node.js core, and userspace code.
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| 4 | *
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| 5 | * Tracing can be enabled with the `--trace-event-categories` command-line flag
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| 6 | * or by using the `trace_events` module. The `--trace-event-categories` flag
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| 7 | * accepts a list of comma-separated category names.
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| 8 | *
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| 9 | * The available categories are:
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| 10 | *
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| 11 | * * `node`: An empty placeholder.
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| 12 | * * `node.async_hooks`: Enables capture of detailed `async_hooks` trace data.
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| 13 | * The `async_hooks` events have a unique `asyncId` and a special `triggerId` `triggerAsyncId` property.
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| 14 | * * `node.bootstrap`: Enables capture of Node.js bootstrap milestones.
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| 15 | * * `node.console`: Enables capture of `console.time()` and `console.count()`output.
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| 16 | * * `node.dns.native`: Enables capture of trace data for DNS queries.
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| 17 | * * `node.environment`: Enables capture of Node.js Environment milestones.
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| 18 | * * `node.fs.sync`: Enables capture of trace data for file system sync methods.
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| 19 | * * `node.perf`: Enables capture of `Performance API` measurements.
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| 20 | * * `node.perf.usertiming`: Enables capture of only Performance API User Timing
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| 21 | * measures and marks.
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| 22 | * * `node.perf.timerify`: Enables capture of only Performance API timerify
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| 23 | * measurements.
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| 24 | * * `node.promises.rejections`: Enables capture of trace data tracking the number
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| 25 | * of unhandled Promise rejections and handled-after-rejections.
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| 26 | * * `node.vm.script`: Enables capture of trace data for the `vm` module's`runInNewContext()`, `runInContext()`, and `runInThisContext()` methods.
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| 27 | * * `v8`: The `V8` events are GC, compiling, and execution related.
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| 28 | *
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| 29 | * By default the `node`, `node.async_hooks`, and `v8` categories are enabled.
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| 30 | *
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| 31 | * ```bash
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| 32 | * node --trace-event-categories v8,node,node.async_hooks server.js
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| 33 | * ```
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| 34 | *
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| 35 | * 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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| 36 | * used and will enable the`node`, `node.async_hooks`, and `v8` trace event categories by default.
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| 37 | *
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| 38 | * ```bash
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| 39 | * node --trace-events-enabled
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| 40 | *
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| 41 | * # is equivalent to
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| 42 | *
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| 43 | * node --trace-event-categories v8,node,node.async_hooks
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| 44 | * ```
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| 45 | *
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| 46 | * Alternatively, trace events may be enabled using the `trace_events` module:
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| 47 | *
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| 48 | * ```js
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| 49 | * const trace_events = require('trace_events');
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| 50 | * const tracing = trace_events.createTracing({ categories: ['node.perf'] });
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| 51 | * tracing.enable(); // Enable trace event capture for the 'node.perf' category
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| 52 | *
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| 53 | * // do work
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| 54 | *
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| 55 | * tracing.disable(); // Disable trace event capture for the 'node.perf' category
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| 56 | * ```
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| 57 | *
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| 58 | * Running Node.js with tracing enabled will produce log files that can be opened
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| 59 | * in the [`chrome://tracing`](https://www.chromium.org/developers/how-tos/trace-event-profiling-tool) tab of Chrome.
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| 60 | *
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| 61 | * 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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| 62 | * be specified with `--trace-event-file-pattern` that accepts a template
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| 63 | * string that supports `${rotation}` and `${pid}`:
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| 64 | *
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| 65 | * ```bash
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| 66 | * node --trace-event-categories v8 --trace-event-file-pattern '${pid}-${rotation}.log' server.js
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| 67 | * ```
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| 68 | *
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| 69 | * The tracing system uses the same time source
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| 70 | * as the one used by `process.hrtime()`.
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| 71 | * However the trace-event timestamps are expressed in microseconds,
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| 72 | * unlike `process.hrtime()` which returns nanoseconds.
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| 73 | *
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| 74 | * The features from this module are not available in `Worker` threads.
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| 75 | * @experimental
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| 76 | * @see [source](https://github.com/nodejs/node/blob/v17.0.0/lib/trace_events.js)
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| 77 | */
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| 78 | declare module 'trace_events' {
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| 79 | /**
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| 80 | * The `Tracing` object is used to enable or disable tracing for sets of
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| 81 | * categories. Instances are created using the
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| 82 | * `trace_events.createTracing()` method.
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| 83 | *
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| 84 | * When created, the `Tracing` object is disabled. Calling the
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| 85 | * `tracing.enable()` method adds the categories to the set of enabled trace
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| 86 | * event categories. Calling `tracing.disable()` will remove the categories
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| 87 | * from the set of enabled trace event categories.
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| 88 | */
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| 89 | interface Tracing {
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| 90 | /**
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| 91 | * A comma-separated list of the trace event categories covered by this
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| 92 | * `Tracing` object.
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| 93 | */
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| 94 | readonly categories: string;
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| 95 | /**
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| 96 | * Disables this `Tracing` object.
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| 97 | *
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| 98 | * Only trace event categories _not_ covered by other enabled `Tracing`
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| 99 | * objects and _not_ specified by the `--trace-event-categories` flag
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| 100 | * will be disabled.
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| 101 | */
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| 102 | disable(): void;
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| 103 | /**
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| 104 | * Enables this `Tracing` object for the set of categories covered by
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| 105 | * the `Tracing` object.
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| 106 | */
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| 107 | enable(): void;
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| 108 | /**
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| 109 | * `true` only if the `Tracing` object has been enabled.
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| 110 | */
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| 111 | readonly enabled: boolean;
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| 112 | }
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| 113 | interface CreateTracingOptions {
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| 114 | /**
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| 115 | * An array of trace category names. Values included in the array are
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| 116 | * coerced to a string when possible. An error will be thrown if the
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| 117 | * value cannot be coerced.
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| 118 | */
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| 119 | categories: string[];
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| 120 | }
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| 121 | /**
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| 122 | * Creates and returns a `Tracing` object for the given set of `categories`.
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| 123 | *
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| 124 | * ```js
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| 125 | * const trace_events = require('trace_events');
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| 126 | * const categories = ['node.perf', 'node.async_hooks'];
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| 127 | * const tracing = trace_events.createTracing({ categories });
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| 128 | * tracing.enable();
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| 129 | * // do stuff
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| 130 | * tracing.disable();
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| 131 | * ```
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| 132 | * @since v10.0.0
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| 133 | * @return .
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| 134 | */
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| 135 | function createTracing(options: CreateTracingOptions): Tracing;
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| 136 | /**
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| 137 | * Returns a comma-separated list of all currently-enabled trace event
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| 138 | * categories. The current set of enabled trace event categories is determined
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| 139 | * by the _union_ of all currently-enabled `Tracing` objects and any categories
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| 140 | * enabled using the `--trace-event-categories` flag.
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| 141 | *
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| 142 | * 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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| 143 | *
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| 144 | * ```js
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| 145 | * const trace_events = require('trace_events');
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| 146 | * const t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });
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| 147 | * const t2 = trace_events.createTracing({ categories: ['node.perf'] });
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| 148 | * const t3 = trace_events.createTracing({ categories: ['v8'] });
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| 149 | *
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| 150 | * t1.enable();
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| 151 | * t2.enable();
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| 152 | *
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| 153 | * console.log(trace_events.getEnabledCategories());
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| 154 | * ```
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| 155 | * @since v10.0.0
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| 156 | */
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| 157 | function getEnabledCategories(): string | undefined;
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| 158 | }
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| 159 | declare module 'node:trace_events' {
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| 160 | export * from 'trace_events';
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| 161 | }
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