209 lines
3.1 KiB
Markdown
209 lines
3.1 KiB
Markdown
---
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id: systrace
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title: Systrace
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layout: docs
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category: APIs
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permalink: docs/systrace.html
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next: timepickerandroid
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previous: stylesheet
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---
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### Methods
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- [`installReactHook`](docs/systrace.html#installreacthook)
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- [`setEnabled`](docs/systrace.html#setenabled)
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- [`isEnabled`](docs/systrace.html#isenabled)
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- [`beginEvent`](docs/systrace.html#beginevent)
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- [`endEvent`](docs/systrace.html#endevent)
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- [`beginAsyncEvent`](docs/systrace.html#beginasyncevent)
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- [`endAsyncEvent`](docs/systrace.html#endasyncevent)
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- [`counterEvent`](docs/systrace.html#counterevent)
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- [`attachToRelayProfiler`](docs/systrace.html#attachtorelayprofiler)
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- [`swizzleJSON`](docs/systrace.html#swizzlejson)
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- [`measureMethods`](docs/systrace.html#measuremethods)
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- [`measure`](docs/systrace.html#measure)
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---
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# Reference
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## Methods
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### `installReactHook()`
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```javascript
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static installReactHook(useFiber)
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```
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---
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### `setEnabled()`
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```javascript
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static setEnabled(enabled)
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```
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---
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### `isEnabled()`
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```javascript
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static isEnabled()
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```
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---
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### `beginEvent()`
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```javascript
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static beginEvent(profileName?, args?)
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```
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beginEvent/endEvent for starting and then ending a profile within the same call stack frame
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---
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### `endEvent()`
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```javascript
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static endEvent()
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```
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---
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### `beginAsyncEvent()`
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```javascript
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static beginAsyncEvent(profileName?)
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```
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beginAsyncEvent/endAsyncEvent for starting and then ending a profile where the end can either
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occur on another thread or out of the current stack frame, eg await
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the returned cookie variable should be used as input into the endAsyncEvent call to end the profile
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---
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### `endAsyncEvent()`
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```javascript
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static endAsyncEvent(profileName?, cookie?)
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```
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---
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### `counterEvent()`
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```javascript
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static counterEvent(profileName?, value?)
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```
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counterEvent registers the value to the profileName on the systrace timeline
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---
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### `attachToRelayProfiler()`
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```javascript
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static attachToRelayProfiler(relayProfiler)
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```
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Relay profiles use await calls, so likely occur out of current stack frame
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therefore async variant of profiling is used
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---
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### `swizzleJSON()`
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```javascript
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static swizzleJSON()
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```
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This is not called by default due to perf overhead but it's useful
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if you want to find traces which spend too much time in JSON.
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---
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### `measureMethods()`
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```javascript
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static measureMethods(object, objectName, methodNames)
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```
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Measures multiple methods of a class. For example, you can do:
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```javascript
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Systrace.measureMethods(JSON, 'JSON', ['parse', 'stringify']);
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```
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**Parameters:**
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| Name | Type | Required | Description |
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| - | - | - | - |
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| object | any | Yes | |
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| objectName | string | Yes | |
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| methodNames | array | Yes| Map from method names to method display names. |
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---
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### `measure()`
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```javascript
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static measure(objName, fnName, func)
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```
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Returns an profiled version of the input function. For example, you can:
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```javascript
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JSON.parse = Systrace.measure('JSON', 'parse', JSON.parse);
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```
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**Parameters:**
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| Name | Type | Required | Description |
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| - | - | - | - |
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| objName | string | Yes | |
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| fnName | string | Yes | |
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| func | function | Yes | |
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