gecko-dev/devtools/server/actors/heap-snapshot-file.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

const protocol = require("devtools/shared/protocol");
const Services = require("Services");

const {
  heapSnapshotFileSpec,
} = require("devtools/shared/specs/heap-snapshot-file");

loader.lazyRequireGetter(
  this,
  "DevToolsUtils",
  "devtools/shared/DevToolsUtils"
);
loader.lazyRequireGetter(this, "OS", "resource://gre/modules/osfile.jsm", true);
loader.lazyRequireGetter(
  this,
  "HeapSnapshotFileUtils",
  "devtools/shared/heapsnapshot/HeapSnapshotFileUtils"
);

/**
 * The HeapSnapshotFileActor handles transferring heap snapshot files from the
 * server to the client. This has to be a global actor in the parent process
 * because child processes are sandboxed and do not have access to the file
 * system.
 */
exports.HeapSnapshotFileActor = protocol.ActorClassWithSpec(
  heapSnapshotFileSpec,
  {
    initialize: function(conn, parent) {
      if (
        Services.appinfo.processType !== Services.appinfo.PROCESS_TYPE_DEFAULT
      ) {
        const err = new Error(
          "Attempt to create a HeapSnapshotFileActor in a " +
            "child process! The HeapSnapshotFileActor *MUST* " +
            "be in the parent process!"
        );
        DevToolsUtils.reportException(
          "HeapSnapshotFileActor.prototype.initialize",
          err
        );
        return;
      }

      protocol.Actor.prototype.initialize.call(this, conn, parent);
    },

    /**
     * @see MemoryFront.prototype.transferHeapSnapshot
     */
    async transferHeapSnapshot(snapshotId) {
      const snapshotFilePath = HeapSnapshotFileUtils.getHeapSnapshotTempFilePath(
        snapshotId
      );
      if (!snapshotFilePath) {
        throw new Error(`No heap snapshot with id: ${snapshotId}`);
      }

      const streamPromise = DevToolsUtils.openFileStream(snapshotFilePath);

      const { size } = await OS.File.stat(snapshotFilePath);
      const bulkPromise = this.conn.startBulkSend({
        actor: this.actorID,
        type: "heap-snapshot",
        length: size,
      });

      const [bulk, stream] = await Promise.all([bulkPromise, streamPromise]);

      try {
        await bulk.copyFrom(stream);
      } finally {
        stream.close();
      }
    },
  }
);