92 lines
2.9 KiB
JavaScript
92 lines
2.9 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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* @providesModule JSEventLoopWatchdog
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* @flow
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*/
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'use strict';
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const infoLog = require('infoLog');
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/* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
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* found when Flow v0.54 was deployed. To see the error delete this comment and
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* run Flow. */
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const performanceNow = require('fbjs/lib/performanceNow');
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type Handler = {
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onIterate?: () => void,
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onStall: (params: {lastInterval: number, busyTime: number}) => ?string,
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};
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/**
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* A utility for tracking stalls in the JS event loop that prevent timers and
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* other events from being processed in a timely manner.
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*
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* The "stall" time is defined as the amount of time in access of the acceptable
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* threshold, which is typically around 100-200ms. So if the treshold is set to
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* 100 and a timer fires 150 ms later than it was scheduled because the event
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* loop was tied up, that would be considered a 50ms stall.
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*
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* By default, logs stall events to the console when installed. Can also be
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* queried with `getStats`.
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*/
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const JSEventLoopWatchdog = {
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getStats: function(): Object {
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return {stallCount, totalStallTime, longestStall, acceptableBusyTime};
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},
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reset: function() {
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infoLog('JSEventLoopWatchdog: reset');
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totalStallTime = 0;
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stallCount = 0;
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longestStall = 0;
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lastInterval = performanceNow();
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},
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addHandler: function(handler: Handler) {
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handlers.push(handler);
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},
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install: function({thresholdMS}: {thresholdMS: number}) {
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acceptableBusyTime = thresholdMS;
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if (installed) {
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return;
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}
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installed = true;
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lastInterval = performanceNow();
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function iteration() {
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const now = performanceNow();
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const busyTime = now - lastInterval;
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if (busyTime >= thresholdMS) {
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const stallTime = busyTime - thresholdMS;
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stallCount++;
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totalStallTime += stallTime;
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longestStall = Math.max(longestStall, stallTime);
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let msg = `JSEventLoopWatchdog: JS thread busy for ${busyTime}ms. ` +
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`${totalStallTime}ms in ${stallCount} stalls so far. `;
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handlers.forEach((handler) => {
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msg += handler.onStall({lastInterval, busyTime}) || '';
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});
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infoLog(msg);
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}
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handlers.forEach((handler) => {
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handler.onIterate && handler.onIterate();
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});
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lastInterval = now;
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setTimeout(iteration, thresholdMS / 5);
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}
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iteration();
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},
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};
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let acceptableBusyTime = 0;
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let installed = false;
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let totalStallTime = 0;
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let stallCount = 0;
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let longestStall = 0;
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let lastInterval = 0;
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const handlers: Array<Handler> = [];
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module.exports = JSEventLoopWatchdog;
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