The Tor Browser: mobile/android/base/sync/repositories/RepositorySession.java@6474c204b198 (annotated)

mobile/android/base/sync/repositories/RepositorySession.java@6474c204b198 (annotated)

mobile/android/base/sync/repositories/RepositorySession.java

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* 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/. */
 package org.mozilla.gecko.sync.repositories;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import org.mozilla.gecko.background.common.log.Logger;
 import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionBeginDelegate;
 import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionFetchRecordsDelegate;
 import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionFinishDelegate;
 import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionGuidsSinceDelegate;
 import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionStoreDelegate;
 import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionWipeDelegate;
 import org.mozilla.gecko.sync.repositories.domain.Record;
 /**
  * A <code>RepositorySession</code> is created and used thusly:
  *
  *<ul>
  * <li>Construct, with a reference to its parent {@link Repository}, by calling
  *   {@link Repository#createSession(RepositorySessionCreationDelegate, android.content.Context)}.</li>
  * <li>Populate with saved information by calling {@link #unbundle(RepositorySessionBundle)}.</li>
  * <li>Begin a sync by calling {@link #begin(RepositorySessionBeginDelegate)}. <code>begin()</code>
  *   is an appropriate place to initialize expensive resources.</li>
  * <li>Perform operations such as {@link #fetchSince(long, RepositorySessionFetchRecordsDelegate)} and
  *   {@link #store(Record)}.</li>
  * <li>Finish by calling {@link #finish(RepositorySessionFinishDelegate)}, retrieving and storing
  *   the current bundle.</li>
  *</ul>
  *
  * If <code>finish()</code> is not called, {@link #abort()} must be called. These calls must
  * <em>always</em> be paired with <code>begin()</code>.
  *
  */
 public abstract class RepositorySession {
   public enum SessionStatus {
     UNSTARTED,
     ACTIVE,
     ABORTED,
     DONE
   }
   private static final String LOG_TAG = "RepositorySession";
   protected static void trace(String message) {
     Logger.trace(LOG_TAG, message);
   }
   private SessionStatus status = SessionStatus.UNSTARTED;
   protected Repository repository;
   protected RepositorySessionStoreDelegate delegate;
   /**
    * A queue of Runnables which call out into delegates.
    */
   protected ExecutorService delegateQueue  = Executors.newSingleThreadExecutor();
   /**
    * A queue of Runnables which effect storing.
    * This includes actual store work, and also the consequences of storeDone.
    * This provides strict ordering.
    */
   protected ExecutorService storeWorkQueue = Executors.newSingleThreadExecutor();
   // The time that the last sync on this collection completed, in milliseconds since epoch.
   private long lastSyncTimestamp = 0;
   public long getLastSyncTimestamp() {
     return lastSyncTimestamp;
   }
   public static long now() {
     return System.currentTimeMillis();
   }
   public RepositorySession(Repository repository) {
     this.repository = repository;
   }
   public abstract void guidsSince(long timestamp, RepositorySessionGuidsSinceDelegate delegate);
   public abstract void fetchSince(long timestamp, RepositorySessionFetchRecordsDelegate delegate);
   public abstract void fetch(String[] guids, RepositorySessionFetchRecordsDelegate delegate) throws InactiveSessionException;
   public abstract void fetchAll(RepositorySessionFetchRecordsDelegate delegate);
   /**
    * Override this if you wish to short-circuit a sync when you know --
    * e.g., by inspecting the database or info/collections -- that no new
    * data are available.
    *
    * @return true if a sync should proceed.
    */
   public boolean dataAvailable() {
     return true;
   }
   /**
    * @return true if we cannot safely sync from this <code>RepositorySession</code>.
    */
   public boolean shouldSkip() {
     return false;
   }
   /*
    * Store operations proceed thusly:
    *
    * * Set a delegate
    * * Store an arbitrary number of records. At any time the delegate can be
    *   notified of an error.
    * * Call storeDone to notify the session that no more items are forthcoming.
    * * The store delegate will be notified of error or completion.
    *
    * This arrangement of calls allows for batching at the session level.
    *
    * Store success calls are not guaranteed.
    */
   public void setStoreDelegate(RepositorySessionStoreDelegate delegate) {
     Logger.debug(LOG_TAG, "Setting store delegate to " + delegate);
     this.delegate = delegate;
   }
   public abstract void store(Record record) throws NoStoreDelegateException;
   public void storeDone() {
     // Our default behavior will be to assume that the Runnable is
     // executed as soon as all the stores synchronously finish, so
     // our end timestamp can just be… now.
     storeDone(now());
   }
   public void storeDone(final long end) {
     Logger.debug(LOG_TAG, "Scheduling onStoreCompleted for after storing is done: " + end);
     Runnable command = new Runnable() {
       @Override
       public void run() {
         delegate.onStoreCompleted(end);
       }
     };
     storeWorkQueue.execute(command);
   }
   public abstract void wipe(RepositorySessionWipeDelegate delegate);
   /**
    * Synchronously perform the shared work of beginning. Throws on failure.
    * @throws InvalidSessionTransitionException
    *
    */
   protected void sharedBegin() throws InvalidSessionTransitionException {
     Logger.debug(LOG_TAG, "Shared begin.");
     if (delegateQueue.isShutdown()) {
       throw new InvalidSessionTransitionException(null);
     }
     if (storeWorkQueue.isShutdown()) {
       throw new InvalidSessionTransitionException(null);
     }
     this.transitionFrom(SessionStatus.UNSTARTED, SessionStatus.ACTIVE);
   }
   /**
    * Start the session. This is an appropriate place to initialize
    * data access components such as database handles.
    *
    * @param delegate
    * @throws InvalidSessionTransitionException
    */
   public void begin(RepositorySessionBeginDelegate delegate) throws InvalidSessionTransitionException {
     sharedBegin();
     delegate.deferredBeginDelegate(delegateQueue).onBeginSucceeded(this);
   }
   public void unbundle(RepositorySessionBundle bundle) {
     this.lastSyncTimestamp = bundle == null ? 0 : bundle.getTimestamp();
   }
   /**
    * Override this in your subclasses to return values to save between sessions.
    * Note that RepositorySession automatically bumps the timestamp to the time
    * the last sync began. If unbundled but not begun, this will be the same as the
    * value in the input bundle.
    *
    * The Synchronizer most likely wants to bump the bundle timestamp to be a value
    * return from a fetch call.
    */
   protected RepositorySessionBundle getBundle() {
     // Why don't we just persist the old bundle?
     long timestamp = getLastSyncTimestamp();
     RepositorySessionBundle bundle = new RepositorySessionBundle(timestamp);
     Logger.debug(LOG_TAG, "Setting bundle timestamp to " + timestamp + ".");
     return bundle;
   }
   /**
    * Just like finish(), but doesn't do any work that should only be performed
    * at the end of a successful sync, and can be called any time.
    */
   public void abort(RepositorySessionFinishDelegate delegate) {
     this.abort();
     delegate.deferredFinishDelegate(delegateQueue).onFinishSucceeded(this, this.getBundle());
   }
   /**
    * Abnormally terminate the repository session, freeing or closing
    * any resources that were opened during the lifetime of the session.
    */
   public void abort() {
     // TODO: do something here.
     this.setStatus(SessionStatus.ABORTED);
     try {
       storeWorkQueue.shutdownNow();
     } catch (Exception e) {
       Logger.error(LOG_TAG, "Caught exception shutting down store work queue.", e);
     }
     try {
       delegateQueue.shutdown();
     } catch (Exception e) {
       Logger.error(LOG_TAG, "Caught exception shutting down delegate queue.", e);
     }
   }
   /**
    * End the repository session, freeing or closing any resources
    * that were opened during the lifetime of the session.
    *
    * @param delegate notified of success or failure.
    * @throws InactiveSessionException
    */
   public void finish(final RepositorySessionFinishDelegate delegate) throws InactiveSessionException {
     try {
       this.transitionFrom(SessionStatus.ACTIVE, SessionStatus.DONE);
       delegate.deferredFinishDelegate(delegateQueue).onFinishSucceeded(this, this.getBundle());
     } catch (InvalidSessionTransitionException e) {
       Logger.error(LOG_TAG, "Tried to finish() an unstarted or already finished session");
       throw new InactiveSessionException(e);
     }
     Logger.trace(LOG_TAG, "Shutting down work queues.");
     storeWorkQueue.shutdown();
     delegateQueue.shutdown();
   }
   /**
    * Run the provided command if we're active and our delegate queue
    * is not shut down.
    */
   protected synchronized void executeDelegateCommand(Runnable command)
       throws InactiveSessionException {
     if (!isActive() || delegateQueue.isShutdown()) {
       throw new InactiveSessionException(null);
     }
     delegateQueue.execute(command);
   }
   public synchronized void ensureActive() throws InactiveSessionException {
     if (!isActive()) {
       throw new InactiveSessionException(null);
     }
   }
   public synchronized boolean isActive() {
     return status == SessionStatus.ACTIVE;
   }
   public synchronized SessionStatus getStatus() {
     return status;
   }
   public synchronized void setStatus(SessionStatus status) {
     this.status = status;
   }
   public synchronized void transitionFrom(SessionStatus from, SessionStatus to) throws InvalidSessionTransitionException {
     if (from == null || this.status == from) {
       Logger.trace(LOG_TAG, "Successfully transitioning from " + this.status + " to " + to);
       this.status = to;
       return;
     }
     Logger.warn(LOG_TAG, "Wanted to transition from " + from + " but in state " + this.status);
     throw new InvalidSessionTransitionException(null);
   }
   /**
    * Produce a record that is some combination of the remote and local records
    * provided.
    *
    * The returned record must be produced without mutating either remoteRecord
    * or localRecord. It is acceptable to return either remoteRecord or localRecord
    * if no modifications are to be propagated.
    *
    * The returned record *should* have the local androidID and the remote GUID,
    * and some optional merge of data from the two records.
    *
    * This method can be called with records that are identical, or differ in
    * any regard.
    *
    * This method will not be called if:
    *
    * * either record is marked as deleted, or
    * * there is no local mapping for a new remote record.
    *
    * Otherwise, it will be called precisely once.
    *
    * Side-effects (e.g., for transactional storage) can be hooked in here.
    *
    * @param remoteRecord
    *        The record retrieved from upstream, already adjusted for clock skew.
    * @param localRecord
    *        The record retrieved from local storage.
    * @param lastRemoteRetrieval
    *        The timestamp of the last retrieved set of remote records, adjusted for
    *        clock skew.
    * @param lastLocalRetrieval
    *        The timestamp of the last retrieved set of local records.
    * @return
    *        A Record instance to apply, or null to apply nothing.
    */
   protected Record reconcileRecords(final Record remoteRecord,
                                     final Record localRecord,
                                     final long lastRemoteRetrieval,
                                     final long lastLocalRetrieval) {
     Logger.debug(LOG_TAG, "Reconciling remote " + remoteRecord.guid + " against local " + localRecord.guid);
     if (localRecord.equalPayloads(remoteRecord)) {
       if (remoteRecord.lastModified > localRecord.lastModified) {
         Logger.debug(LOG_TAG, "Records are equal. No record application needed.");
         return null;
       }
       // Local wins.
       return null;
     }
     // TODO: Decide what to do based on:
     // * Which of the two records is modified;
     // * Whether they are equal or congruent;
     // * The modified times of each record (interpreted through the lens of clock skew);
     // * ...
     boolean localIsMoreRecent = localRecord.lastModified > remoteRecord.lastModified;
     Logger.debug(LOG_TAG, "Local record is more recent? " + localIsMoreRecent);
     Record donor = localIsMoreRecent ? localRecord : remoteRecord;
     // Modify the local record to match the remote record's GUID and values.
     // Preserve the local Android ID, and merge data where possible.
     // It sure would be nice if copyWithIDs didn't give a shit about androidID, mm?
     Record out = donor.copyWithIDs(remoteRecord.guid, localRecord.androidID);
     // We don't want to upload the record if the remote record was
     // applied without changes.
     // This logic will become more complicated as reconciling becomes smarter.
     if (!localIsMoreRecent) {
       trackGUID(out.guid);
     }
     return out;
   }
   /**
    * Depending on the RepositorySession implementation, track
    * that a record — most likely a brand-new record that has been
    * applied unmodified — should be tracked so as to not be uploaded
    * redundantly.
    *
    * The default implementations do nothing.
    */
   protected void trackGUID(String guid) {
   }
   protected synchronized void untrackGUIDs(Collection<String> guids) {
   }
   protected void untrackGUID(String guid) {
   }
   // Ah, Java. You wretched creature.
   public Iterator<String> getTrackedRecordIDs() {
     return new ArrayList<String>().iterator();
   }
 }

The Tor Browser / annotate

mobile/android/base/sync/repositories/RepositorySession.java@6474c204b198 (annotated)

mobile/android/base/sync/repositories/RepositorySession.java