Merge pull request opentripplanner#5974 from entur/publish_timetable_…

…snapshot_in_background

Publish timetable snapshot in background

src/ext/java/org/opentripplanner/ext/siri/SiriTimetableSnapshotSource.java

@@ -57,7 +57,12 @@ public class SiriTimetableSnapshotSource implements TimetableSnapshotProvider {
    */
   private final SiriTripPatternCache tripPatternCache;
 
-  private final TransitEditorService transitService;
+  /**
+   * Long-lived transit editor service that has access to the timetable snapshot buffer.
+   * This differs from the usual use case where the transit service refers to the latest published
+   * timetable snapshot.
+   */
+  private final TransitEditorService transitEditorService;
 
   private final TimetableSnapshotManager snapshotManager;
 
@@ -71,9 +76,10 @@ public SiriTimetableSnapshotSource(
         parameters,
         () -> LocalDate.now(transitModel.getTimeZone())
       );
-    this.transitService = new DefaultTransitService(transitModel);
+    this.transitEditorService =
+      new DefaultTransitService(transitModel, getTimetableSnapshotBuffer());
     this.tripPatternCache =
-      new SiriTripPatternCache(tripPatternIdGenerator, transitService::getPatternForTrip);
+      new SiriTripPatternCache(tripPatternIdGenerator, transitEditorService::getPatternForTrip);
 
     transitModel.initTimetableSnapshotProvider(this);
   }
@@ -102,26 +108,22 @@ public UpdateResult applyEstimatedTimetable(
 
     List<Result<UpdateSuccess, UpdateError>> results = new ArrayList<>();
 
-    snapshotManager.withLock(() -> {
-      if (incrementality == FULL_DATASET) {
-        // Remove all updates from the buffer
-        snapshotManager.clearBuffer(feedId);
-      }
+    if (incrementality == FULL_DATASET) {
+      // Remove all updates from the buffer
+      snapshotManager.clearBuffer(feedId);
+    }
 
-      for (var etDelivery : updates) {
-        for (var estimatedJourneyVersion : etDelivery.getEstimatedJourneyVersionFrames()) {
-          var journeys = estimatedJourneyVersion.getEstimatedVehicleJourneies();
-          LOG.debug("Handling {} EstimatedVehicleJourneys.", journeys.size());
-          for (EstimatedVehicleJourney journey : journeys) {
-            results.add(apply(journey, transitService, fuzzyTripMatcher, entityResolver));
-          }
+    for (var etDelivery : updates) {
+      for (var estimatedJourneyVersion : etDelivery.getEstimatedJourneyVersionFrames()) {
+        var journeys = estimatedJourneyVersion.getEstimatedVehicleJourneies();
+        LOG.debug("Handling {} EstimatedVehicleJourneys.", journeys.size());
+        for (EstimatedVehicleJourney journey : journeys) {
+          results.add(apply(journey, transitEditorService, fuzzyTripMatcher, entityResolver));
         }
       }
+    }
 
-      LOG.debug("message contains {} trip updates", updates.size());
-
-      snapshotManager.purgeAndCommit();
-    });
+    LOG.debug("message contains {} trip updates", updates.size());
 
     return UpdateResult.ofResults(results);
   }
@@ -131,6 +133,10 @@ public TimetableSnapshot getTimetableSnapshot() {
     return snapshotManager.getTimetableSnapshot();
   }
 
+  private TimetableSnapshot getTimetableSnapshotBuffer() {
+    return snapshotManager.getTimetableSnapshotBuffer();
+  }
+
   private Result<UpdateSuccess, UpdateError> apply(
     EstimatedVehicleJourney journey,
     TransitEditorService transitService,
@@ -195,11 +201,7 @@ private boolean shouldAddNewTrip(
    * Snapshot timetable is used as source if initialised, trip patterns scheduled timetable if not.
    */
   private Timetable getCurrentTimetable(TripPattern tripPattern, LocalDate serviceDate) {
-    TimetableSnapshot timetableSnapshot = getTimetableSnapshot();
-    if (timetableSnapshot != null) {
-      return timetableSnapshot.resolve(tripPattern, serviceDate);
-    }
-    return tripPattern.getScheduledTimetable();
+    return getTimetableSnapshotBuffer().resolve(tripPattern, serviceDate);
   }
 
   private Result<TripUpdate, UpdateError> handleModifiedTrip(
@@ -228,7 +230,7 @@ private Result<TripUpdate, UpdateError> handleModifiedTrip(
 
     if (trip != null) {
       // Found exact match
-      pattern = transitService.getPatternForTrip(trip);
+      pattern = transitEditorService.getPatternForTrip(trip);
     } else if (fuzzyTripMatcher != null) {
       // No exact match found - search for trips based on arrival-times/stop-patterns
       TripAndPattern tripAndPattern = fuzzyTripMatcher.match(
@@ -263,7 +265,7 @@ private Result<TripUpdate, UpdateError> handleModifiedTrip(
       pattern,
       estimatedVehicleJourney,
       serviceDate,
-      transitService.getTimeZone(),
+      transitEditorService.getTimeZone(),
       entityResolver
     )
       .build();
@@ -310,7 +312,7 @@ private Result<UpdateSuccess, UpdateError> addTripToGraphAndBuffer(TripUpdate tr
   private boolean markScheduledTripAsDeleted(Trip trip, final LocalDate serviceDate) {
     boolean success = false;
 
-    final TripPattern pattern = transitService.getPatternForTrip(trip);
+    final TripPattern pattern = transitEditorService.getPatternForTrip(trip);
 
     if (pattern != null) {
       // Mark scheduled trip times for this trip in this pattern as deleted
@@ -329,4 +331,11 @@ private boolean markScheduledTripAsDeleted(Trip trip, final LocalDate serviceDat
 
     return success;
   }
+
+  /**
+   * Flush pending changes in the timetable snapshot buffer and publish a new snapshot.
+   */
+  public void flushBuffer() {
+    snapshotManager.purgeAndCommit();
+  }
 }

src/main/java/org/opentripplanner/model/TimetableSnapshot.java

@@ -65,6 +65,11 @@
  * up timetables on this class could conceivably be replaced with snapshotting entire views of the
  * transit network. It would also be possible to make the realtime version of Timetables or
  * TripTimes the primary view, and include references back to their scheduled versions.
+ * <p>
+ * Implementation note: when a snapshot is committed, the mutable state of this class is stored
+ * in final fields and completely initialized in the constructor. This provides an additional
+ * guarantee of safe-publication without synchronization.
+ * (see <a href="https://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.5">final Field Semantics</a>)
  */
 public class TimetableSnapshot {
 

src/main/java/org/opentripplanner/transit/service/DefaultTransitService.java

@@ -79,6 +79,14 @@ public DefaultTransitService(TransitModel transitModel) {
     this.transitModelIndex = transitModel.getTransitModelIndex();
   }
 
+  public DefaultTransitService(
+    TransitModel transitModel,
+    TimetableSnapshot timetableSnapshotBuffer
+  ) {
+    this(transitModel);
+    this.timetableSnapshot = timetableSnapshotBuffer;
+  }
+
   @Override
   public Collection<String> getFeedIds() {
     return this.transitModel.getFeedIds();

src/main/java/org/opentripplanner/updater/configure/UpdaterConfigurator.java

@@ -2,6 +2,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 import org.opentripplanner.ext.siri.SiriTimetableSnapshotSource;
 import org.opentripplanner.ext.siri.updater.SiriETUpdater;
 import org.opentripplanner.ext.siri.updater.SiriSXUpdater;
@@ -20,6 +21,7 @@
 import org.opentripplanner.updater.UpdatersParameters;
 import org.opentripplanner.updater.alert.GtfsRealtimeAlertsUpdater;
 import org.opentripplanner.updater.spi.GraphUpdater;
+import org.opentripplanner.updater.spi.TimetableSnapshotFlush;
 import org.opentripplanner.updater.trip.MqttGtfsRealtimeUpdater;
 import org.opentripplanner.updater.trip.PollingTripUpdater;
 import org.opentripplanner.updater.trip.TimetableSnapshotSource;
@@ -94,6 +96,9 @@ private void configure() {
     );
 
     GraphUpdaterManager updaterManager = new GraphUpdaterManager(graph, transitModel, updaters);
+
+    configureTimetableSnapshotFlush(updaterManager);
+
     updaterManager.startUpdaters();
 
     // Stop the updater manager if it contains nothing
@@ -223,4 +228,21 @@ private TimetableSnapshotSource provideGtfsTimetableSnapshot() {
     }
     return gtfsTimetableSnapshotSource;
   }
+
+  /**
+   * If SIRI or GTFS real-time updaters are in use, configure a periodic flush of the timetable
+   * snapshot.
+   */
+  private void configureTimetableSnapshotFlush(GraphUpdaterManager updaterManager) {
+    if (siriTimetableSnapshotSource != null || gtfsTimetableSnapshotSource != null) {
+      updaterManager
+        .getScheduler()
+        .scheduleWithFixedDelay(
+          new TimetableSnapshotFlush(siriTimetableSnapshotSource, gtfsTimetableSnapshotSource),
+          0,
+          updatersParameters.timetableSnapshotParameters().maxSnapshotFrequency().toSeconds(),
+          TimeUnit.SECONDS
+        );
+    }
+  }
 }

src/main/java/org/opentripplanner/updater/spi/TimetableSnapshotFlush.java

@@ -0,0 +1,43 @@
+package org.opentripplanner.updater.spi;
+
+import org.opentripplanner.ext.siri.SiriTimetableSnapshotSource;
+import org.opentripplanner.updater.trip.TimetableSnapshotSource;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Flush the timetable snapshot buffer by committing pending changes.
+ * Exceptions occurring during the flush are caught and ignored: the scheduler can then retry
+ * the task later.
+ */
+public class TimetableSnapshotFlush implements Runnable {
+
+  private static final Logger LOG = LoggerFactory.getLogger(TimetableSnapshotFlush.class);
+
+  private final SiriTimetableSnapshotSource siriTimetableSnapshotSource;
+  private final TimetableSnapshotSource gtfsTimetableSnapshotSource;
+
+  public TimetableSnapshotFlush(
+    SiriTimetableSnapshotSource siriTimetableSnapshotSource,
+    TimetableSnapshotSource gtfsTimetableSnapshotSource
+  ) {
+    this.siriTimetableSnapshotSource = siriTimetableSnapshotSource;
+    this.gtfsTimetableSnapshotSource = gtfsTimetableSnapshotSource;
+  }
+
+  @Override
+  public void run() {
+    try {
+      LOG.debug("Flushing timetable snapshot buffer");
+      if (siriTimetableSnapshotSource != null) {
+        siriTimetableSnapshotSource.flushBuffer();
+      }
+      if (gtfsTimetableSnapshotSource != null) {
+        gtfsTimetableSnapshotSource.flushBuffer();
+      }
+      LOG.debug("Flushed timetable snapshot buffer");
+    } catch (Throwable t) {
+      LOG.error("Error flushing timetable snapshot buffer", t);
+    }
+  }
+}

src/main/java/org/opentripplanner/updater/trip/TimetableSnapshotManager.java

@@ -2,13 +2,12 @@
 
 import java.time.LocalDate;
 import java.util.Objects;
-import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Supplier;
 import javax.annotation.Nullable;
-import org.opentripplanner.framework.time.CountdownTimer;
 import org.opentripplanner.model.Timetable;
 import org.opentripplanner.model.TimetableSnapshot;
 import org.opentripplanner.routing.algorithm.raptoradapter.transit.mappers.TransitLayerUpdater;
+import org.opentripplanner.routing.util.ConcurrentPublished;
 import org.opentripplanner.transit.model.framework.FeedScopedId;
 import org.opentripplanner.transit.model.framework.Result;
 import org.opentripplanner.transit.model.network.TripPattern;
@@ -30,36 +29,18 @@ public final class TimetableSnapshotManager {
 
   private static final Logger LOG = LoggerFactory.getLogger(TimetableSnapshotManager.class);
   private final TransitLayerUpdater transitLayerUpdater;
-  /**
-   * Lock to indicate that buffer is in use
-   */
-  private final ReentrantLock bufferLock = new ReentrantLock(true);
 
   /**
-   * The working copy of the timetable snapshot. Should not be visible to routing threads. Should
-   * only be modified by a thread that holds a lock on {@link #bufferLock}. All public methods that
-   * might modify this buffer will correctly acquire the lock. By design, only one thread should
-   * ever be writing to this buffer.
-   * TODO RT_AB: research and document why this lock is needed since only one thread should ever be
-   *   writing to this buffer. One possible reason may be a need to suspend writes while indexing
-   *   and swapping out the buffer. But the original idea was to make a new copy of the buffer
-   *   before re-indexing it. While refactoring or rewriting parts of this system, we could throw
-   *   an exception if a writing section is entered by more than one thread.
+   * The working copy of the timetable snapshot. Should not be visible to routing threads.
+   * By design, only one thread should ever be writing to this buffer.
    */
   private final TimetableSnapshot buffer = new TimetableSnapshot();
 
   /**
    * The last committed snapshot that was handed off to a routing thread. This snapshot may be given
-   * to more than one routing thread if the maximum snapshot frequency is exceeded.
-   */
-  private volatile TimetableSnapshot snapshot = null;
-
-  /**
-   * If a timetable snapshot is requested less than this number of milliseconds after the previous
-   * snapshot, just return the same one. Throttles the potentially resource-consuming task of
-   * duplicating a TripPattern -> Timetable map and indexing the new Timetables.
+   * to more than one routing thread.
    */
-  private final CountdownTimer snapshotFrequencyThrottle;
+  private final ConcurrentPublished<TimetableSnapshot> snapshot = new ConcurrentPublished<>();
 
   /**
    * Should expired real-time data be purged from the graph.
@@ -85,7 +66,6 @@ public TimetableSnapshotManager(
     Supplier<LocalDate> localDateNow
   ) {
     this.transitLayerUpdater = transitLayerUpdater;
-    this.snapshotFrequencyThrottle = new CountdownTimer(parameters.maxSnapshotFrequency());
     this.purgeExpiredData = parameters.purgeExpiredData();
     this.localDateNow = Objects.requireNonNull(localDateNow);
     // Force commit so that snapshot initializes
@@ -99,19 +79,17 @@ public TimetableSnapshotManager(
    * to the snapshot to release resources.
    */
   public TimetableSnapshot getTimetableSnapshot() {
-    // Try to get a lock on the buffer
-    if (bufferLock.tryLock()) {
-      // Make a new snapshot if necessary
-      try {
-        commitTimetableSnapshot(false);
-        return snapshot;
-      } finally {
-        bufferLock.unlock();
-      }
-    }
-    // No lock could be obtained because there is either a snapshot commit busy or updates
-    // are applied at this moment, just return the current snapshot
-    return snapshot;
+    return snapshot.get();
+  }
+
+  /**
+   * @return the current timetable snapshot buffer that contains pending changes (not yet published
+   * in a snapshot).
+   * This should be used in the context of an updater to build a TransitEditorService that sees all
+   * the changes applied so far by real-time updates.
+   */
+  public TimetableSnapshot getTimetableSnapshotBuffer() {
+    return buffer;
   }
 
   /**
@@ -122,21 +100,12 @@ public TimetableSnapshot getTimetableSnapshot() {
    *
    * @param force Force the committing of a new snapshot even if the above conditions are not met.
    */
-  public void commitTimetableSnapshot(final boolean force) {
-    if (force || snapshotFrequencyThrottle.timeIsUp()) {
-      if (force || buffer.isDirty()) {
-        LOG.debug("Committing {}", buffer);
-        snapshot = buffer.commit(transitLayerUpdater, force);
-
-        // We only reset the timer when the snapshot is updated. This will cause the first
-        // update to be committed after a silent period. This should not have any effect in
-        // a busy updater. It is however useful when manually testing the updater.
-        snapshotFrequencyThrottle.restart();
-      } else {
-        LOG.debug("Buffer was unchanged, keeping old snapshot.");
-      }
+  void commitTimetableSnapshot(final boolean force) {
+    if (force || buffer.isDirty()) {
+      LOG.debug("Committing {}", buffer);
+      snapshot.publish(buffer.commit(transitLayerUpdater, force));
     } else {
-      LOG.debug("Snapshot frequency exceeded. Reusing snapshot {}", snapshot);
+      LOG.debug("Buffer was unchanged, keeping old snapshot.");
     }
   }
 
@@ -205,22 +174,6 @@ private boolean purgeExpiredData() {
     return buffer.purgeExpiredData(previously);
   }
 
-  /**
-   * Execute a {@code Runnable} with a locked snapshot buffer and release the lock afterwards. While
-   * the action of locking and unlocking is not complicated to do for calling code, this method
-   * exists so that the lock instance is a private field.
-   */
-  public void withLock(Runnable action) {
-    bufferLock.lock();
-
-    try {
-      action.run();
-    } finally {
-      // Always release lock
-      bufferLock.unlock();
-    }
-  }
-
   /**
    * Clear all data of snapshot for the provided feed id
    */