fune/browser/components/extensions/parent/ext-geckoProfiler.js

/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
/* vim: set sts=2 sw=2 et tw=80: */
"use strict";

var {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");

ChromeUtils.defineModuleGetter(this, "OS", "resource://gre/modules/osfile.jsm");
ChromeUtils.defineModuleGetter(this, "ProfilerGetSymbols", "resource://app/modules/ProfilerGetSymbols.jsm");

const PREF_ASYNC_STACK = "javascript.options.asyncstack";

const ASYNC_STACKS_ENABLED = Services.prefs.getBoolPref(PREF_ASYNC_STACK, false);

var {
  ExtensionError,
} = ExtensionUtils;

const symbolCache = new Map();

const primeSymbolStore = libs => {
  for (const {path, debugName, debugPath, breakpadId} of libs) {
    symbolCache.set(`${debugName}/${breakpadId}`, {path, debugPath});
  }
};

const isRunningObserver = {
  _observers: new Set(),

  observe(subject, topic, data) {
    switch (topic) {
      case "profiler-started":
      case "profiler-stopped":
        // Call observer(false) or observer(true), but do it through a promise
        // so that it's asynchronous.
        // We don't want it to be synchronous because of the observer call in
        // addObserver, which is asynchronous, and we want to get the ordering
        // right.
        const isRunningPromise = Promise.resolve(topic === "profiler-started");
        for (let observer of this._observers) {
          isRunningPromise.then(observer);
        }
        break;
    }
  },

  _startListening() {
    Services.obs.addObserver(this, "profiler-started");
    Services.obs.addObserver(this, "profiler-stopped");
  },

  _stopListening() {
    Services.obs.removeObserver(this, "profiler-started");
    Services.obs.removeObserver(this, "profiler-stopped");
  },

  addObserver(observer) {
    if (this._observers.size === 0) {
      this._startListening();
    }

    this._observers.add(observer);
    observer(Services.profiler.IsActive());
  },

  removeObserver(observer) {
    if (this._observers.delete(observer) && this._observers.size === 0) {
      this._stopListening();
    }
  },
};

this.geckoProfiler = class extends ExtensionAPI {
  getAPI(context) {
    return {
      geckoProfiler: {
        async start(options) {
          const {bufferSize, windowLength, interval, features, threads} = options;

          Services.prefs.setBoolPref(PREF_ASYNC_STACK, false);
          if (threads) {
            Services.profiler.StartProfiler(bufferSize, interval,
                                            features, features.length,
                                            threads, threads.length,
                                            windowLength);
          } else {
            Services.profiler.StartProfiler(bufferSize, interval,
                                            features, features.length,
                                            [], 0,
                                            windowLength);
          }
        },

        async stop() {
          if (ASYNC_STACKS_ENABLED !== null) {
            Services.prefs.setBoolPref(PREF_ASYNC_STACK, ASYNC_STACKS_ENABLED);
          }

          Services.profiler.StopProfiler();
        },

        async pause() {
          Services.profiler.PauseSampling();
        },

        async resume() {
          Services.profiler.ResumeSampling();
        },

        async getProfile() {
          if (!Services.profiler.IsActive()) {
            throw new ExtensionError("The profiler is stopped. " +
              "You need to start the profiler before you can capture a profile.");
          }

          return Services.profiler.getProfileDataAsync();
        },

        async getProfileAsArrayBuffer() {
          if (!Services.profiler.IsActive()) {
            throw new ExtensionError("The profiler is stopped. " +
              "You need to start the profiler before you can capture a profile.");
          }

          return Services.profiler.getProfileDataAsArrayBuffer();
        },

        async getSymbols(debugName, breakpadId) {
          if (symbolCache.size === 0) {
            primeSymbolStore(Services.profiler.sharedLibraries);
          }

          const cachedLibInfo = symbolCache.get(`${debugName}/${breakpadId}`);
          if (!cachedLibInfo) {
            throw new Error(
              `The library ${debugName} ${breakpadId} is not in the Services.profiler.sharedLibraries list, ` +
              "so the local path for it is not known and symbols for it can not be obtained. " +
              "This usually happens if a content process uses a library that's not used in the parent " +
              "process - Services.profiler.sharedLibraries only knows about libraries in the parent process.");
          }

          const {path, debugPath} = cachedLibInfo;
          if (!OS.Path.split(path).absolute) {
            throw new Error(
              `Services.profiler.sharedLibraries did not contain an absolute path for the library ${debugName} ${breakpadId}, ` +
              "so symbols for this library can not be obtained.");
          }

          return ProfilerGetSymbols.getSymbolTable(path, debugPath, breakpadId);
        },

        onRunning: new EventManager({
          context,
          name: "geckoProfiler.onRunning",
          register: fire => {
            isRunningObserver.addObserver(fire.async);
            return () => {
              isRunningObserver.removeObserver(fire.async);
            };
          },
        }).api(),
      },
    };
  }
};