Wireframe scheduler implementation

chrome/android/java/src/org/chromium/chrome/browser/offlinepages/BackgroundTask.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.offlinepages;
+
+import android.content.Context;
+import android.os.Bundle;
+
+import org.chromium.base.Log;
+import org.chromium.chrome.browser.profiles.Profile;
+
+import java.util.concurrent.CountDownLatch;
+
+/**
+ * Handles servicing of background offlining requests coming via the GCMNetworkManager.

[dougarnett, 2016/05/20 22:17:32]

nit: GcmNetworkManager is the actual capitalization

[Pete Williamson, 2016/05/23 19:36:31]

Done.

+ */
+public class BackgroundTask implements BackgroundSchedulerBridge.ProcessingDoneCallback {
+    private static final String TAG = "BackgroundTask";
+    /**
+     * Triggers processing of background offlining requests.  This is called when
+     * system conditions are appropriate for background offlining, typically from the
+     * GcmTaskService onRunTask() method.  In response, we will start the
+     * task processing by passing the call along to the C++ RequestCoordinator.
+     *
+     * @returns true for success
+     */
+    public boolean processBackgroundReqeusts(Context context, Bundle bundle) {

[dougarnett, 2016/05/20 22:17:32]

spelling of Requests

[Pete Williamson, 2016/05/23 19:36:31]

Done.

+        mProcessingDoneLatch = new CountDownLatch(1);
+
+        // TODO(petewil): Decode the TriggerConditions from the bundle.
+
+        // TODO(petewil): We only have a context.  Is this a reasonable way to get a profile?
+        Profile profile = Profile.getLastUsedProfile();
+        if (profile.isOffTheRecord()) {
+            profile = profile.getOriginalProfile();
+        }
+
+        // Make sure the bridge has a pointer to the proper profile and context.
+        BackgroundSchedulerBridge.getForProfile(profile, context);
+        // Pass the activation on to the bridge to the C++ RequestCoordinator.
+        BackgroundSchedulerBridge.startProcessing(context, this);
+
+        // Gather UMA data to measure how often the user's machine is amenable to background
+        // loading when we wake to do a task.
+        OfflinePageUtils.recordWakeupUMA(context);
+
+        // Wait for callback async completion before returning.  This is important so
+        // we don't start the next GCM task until we are done with this one.  It also
+        // rate limits our pre-render calls, and holds the wake lock for us.
+        try {
+            // TODO(petewil): Add a timeout here in case pre-rendering hangs.
+            mProcessingDoneLatch.await();

[dewittj, 2016/05/20 21:52:31]

Based on the call flow, this will block the UI thread:

onRunTask -> runOnUiThread -> handleOfflinePageBackgroundLoad ->
task.processBackgroundReqeusts

Needs refactoring to avoid that.

[dougarnett, 2016/05/20 22:30:18]

Nice catch!  

We might want a thread check entering this method if we expect/need it to not be
UI thread.

[Pete Williamson, 2016/05/23 19:36:31]

The intent is for this to block the incoming thread.  However, GCM Network
Manager promises us that we will not be called on the UI thread. Added a check
that we don't get called on the UI thread.

[Pete Williamson, 2016/05/23 19:36:31]

Check addded.

[dougarnett, 2016/05/24 16:27:58]

Added comment to the runOnUiThread call to make this issue more clear. Let's
discuss this afternoon.

[dewittj, 2016/05/24 16:56:19]

Can you point me to where this promise is made?  I haven't seen any reference to
which thread we'll be called on in the docs.

+        } catch (InterruptedException e) {
+            Log.w(TAG, "IncomingTask interrupted, returning to GcmNetworkManager");
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Callback function which indicates completion of background work.
+     * @param result - TODO(petewil): What is this for again?  What does true mean?
+     */
+    public void onProcessingDone(boolean result) {
+        mProcessingDoneLatch.countDown();
+    }
+
+    private CountDownLatch mProcessingDoneLatch;
+}