86 lines
3.1 KiB
Markdown
86 lines
3.1 KiB
Markdown
# contentTracing
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> Collect tracing data from Chromium to find performance bottlenecks and slow operations.
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Process: [Main](../glossary.md#main-process)
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This module does not include a web interface. To view recorded traces, use
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[trace viewer][], available at `chrome://tracing` in Chrome.
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**Note:** You should not use this module until the `ready` event of the app
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module is emitted.
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```javascript
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const { app, contentTracing } = require('electron')
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app.whenReady().then(() => {
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(async () => {
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await contentTracing.startRecording({
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included_categories: ['*']
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})
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console.log('Tracing started')
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await new Promise(resolve => setTimeout(resolve, 5000))
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const path = await contentTracing.stopRecording()
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console.log('Tracing data recorded to ' + path)
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})()
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})
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```
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## Methods
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The `contentTracing` module has the following methods:
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### `contentTracing.getCategories()`
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Returns `Promise<string[]>` - resolves with an array of category groups once all child processes have acknowledged the `getCategories` request
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Get a set of category groups. The category groups can change as new code paths
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are reached. See also the [list of built-in tracing
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categories](https://chromium.googlesource.com/chromium/src/+/master/base/trace_event/builtin_categories.h).
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> **NOTE:** Electron adds a non-default tracing category called `"electron"`.
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> This category can be used to capture Electron-specific tracing events.
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### `contentTracing.startRecording(options)`
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* `options` ([TraceConfig](structures/trace-config.md) | [TraceCategoriesAndOptions](structures/trace-categories-and-options.md))
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Returns `Promise<void>` - resolved once all child processes have acknowledged the `startRecording` request.
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Start recording on all processes.
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Recording begins immediately locally and asynchronously on child processes
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as soon as they receive the EnableRecording request.
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If a recording is already running, the promise will be immediately resolved, as
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only one trace operation can be in progress at a time.
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### `contentTracing.stopRecording([resultFilePath])`
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* `resultFilePath` string (optional)
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Returns `Promise<string>` - resolves with a path to a file that contains the traced data once all child processes have acknowledged the `stopRecording` request
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Stop recording on all processes.
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Child processes typically cache trace data and only rarely flush and send
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trace data back to the main process. This helps to minimize the runtime overhead
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of tracing since sending trace data over IPC can be an expensive operation. So,
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to end tracing, Chromium asynchronously asks all child processes to flush any
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pending trace data.
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Trace data will be written into `resultFilePath`. If `resultFilePath` is empty
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or not provided, trace data will be written to a temporary file, and the path
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will be returned in the promise.
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### `contentTracing.getTraceBufferUsage()`
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Returns `Promise<Object>` - Resolves with an object containing the `value` and `percentage` of trace buffer maximum usage
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* `value` number
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* `percentage` number
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Get the maximum usage across processes of trace buffer as a percentage of the
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full state.
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[trace viewer]: https://chromium.googlesource.com/catapult/+/HEAD/tracing/README.md
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