Implement position buffering

3 files changed, 124 insertions, 4 deletions

diff --git a/src/main/java/org/traccar/ProcessingHandler.java b/src/main/java/org/traccar/ProcessingHandler.java
index 688389d98..cbb375a72 100644
--- a/src/main/java/org/traccar/ProcessingHandler.java
+++ b/src/main/java/org/traccar/ProcessingHandler.java
@@ -21,12 +21,13 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
 import jakarta.inject.Inject;
 import jakarta.inject.Singleton;
+import org.traccar.config.Config;
+import org.traccar.database.BufferingManager;
 import org.traccar.database.NotificationManager;
 import org.traccar.handler.BasePositionHandler;
 import org.traccar.handler.ComputedAttributesHandler;
 import org.traccar.handler.CopyAttributesHandler;
 import org.traccar.handler.DatabaseHandler;
-import org.traccar.handler.PostProcessHandler;
 import org.traccar.handler.DistanceHandler;
 import org.traccar.handler.EngineHoursHandler;
 import org.traccar.handler.FilterHandler;
@@ -36,6 +37,7 @@ import org.traccar.handler.GeolocationHandler;
 import org.traccar.handler.HemisphereHandler;
 import org.traccar.handler.MotionHandler;
 import org.traccar.handler.PositionForwardingHandler;
+import org.traccar.handler.PostProcessHandler;
 import org.traccar.handler.SpeedLimitHandler;
 import org.traccar.handler.TimeHandler;
 import org.traccar.handler.events.AlertEventHandler;
@@ -62,19 +64,21 @@ import java.util.stream.Stream;
 
 @Singleton
 @ChannelHandler.Sharable
-public class ProcessingHandler extends ChannelInboundHandlerAdapter {
+public class ProcessingHandler extends ChannelInboundHandlerAdapter implements BufferingManager.Callback {
 
     private final NotificationManager notificationManager;
     private final PositionLogger positionLogger;
+    private final BufferingManager bufferingManager;
     private final List<BasePositionHandler> positionHandlers;
     private final List<BaseEventHandler> eventHandlers;
     private final PostProcessHandler postProcessHandler;
 
     @Inject
     public ProcessingHandler(
-            Injector injector, NotificationManager notificationManager, PositionLogger positionLogger) {
+            Injector injector, Config config, NotificationManager notificationManager, PositionLogger positionLogger) {
         this.notificationManager = notificationManager;
         this.positionLogger = positionLogger;
+        bufferingManager = new BufferingManager(config, this);
 
         positionHandlers = Stream.of(
                 TimeHandler.class,
@@ -117,12 +121,17 @@ public class ProcessingHandler extends ChannelInboundHandlerAdapter {
     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
         if (msg instanceof Position) {
-            processPositionHandlers(ctx, (Position) msg);
+            bufferingManager.accept(ctx, (Position) msg);
         } else {
             super.channelRead(ctx, msg);
         }
     }
 
+    @Override
+    public void onReleased(ChannelHandlerContext context, Position position) {
+        processPositionHandlers(context, position);
+    }
+
     private void processPositionHandlers(ChannelHandlerContext ctx, Position position) {
         var iterator = positionHandlers.iterator();
         iterator.next().handlePosition(position, new BasePositionHandler.Callback() {
diff --git a/src/main/java/org/traccar/config/Keys.java b/src/main/java/org/traccar/config/Keys.java
index 4aacb2cd8..d346084bd 100644
--- a/src/main/java/org/traccar/config/Keys.java
+++ b/src/main/java/org/traccar/config/Keys.java
@@ -293,6 +293,14 @@ public final class Keys {
             false);
 
     /**
+     * If not zero, enable buffering of incoming data to handle ordering locations. The value is threshold for
+     * buffering in milliseconds.
+     */
+    public static final ConfigKey<Long> SERVER_BUFFERING_THRESHOLD = new LongConfigKey(
+            "server.buffering.threshold",
+            List.of(KeyType.CONFIG));
+
+    /**
      * Server wide connection timeout value in seconds. See protocol timeout for more information.
      */
     public static final ConfigKey<Integer> SERVER_TIMEOUT = new IntegerConfigKey(
diff --git a/src/main/java/org/traccar/database/BufferingManager.java b/src/main/java/org/traccar/database/BufferingManager.java
new file mode 100644
index 000000000..ab71b2860
--- /dev/null
+++ b/src/main/java/org/traccar/database/BufferingManager.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2024 Anton Tananaev (anton@traccar.org)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.traccar.database;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.util.HashedWheelTimer;
+import io.netty.util.Timeout;
+import io.netty.util.Timer;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.traccar.config.Config;
+import org.traccar.config.Keys;
+import org.traccar.model.Position;
+
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.TreeSet;
+import java.util.concurrent.TimeUnit;
+
+public class BufferingManager {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(BufferingManager.class);
+
+    public interface Callback {
+        void onReleased(ChannelHandlerContext context, Position position);
+    }
+
+    private static class Holder implements Comparable<Holder> {
+
+        private static final Comparator<Position> COMPARATOR = Comparator
+                .comparing(Position::getFixTime)
+                .thenComparing(Position::getDeviceTime)
+                .thenComparing(Position::getServerTime);
+
+        private final ChannelHandlerContext context;
+        private final Position position;
+        private Timeout timeout;
+
+        private Holder(ChannelHandlerContext context, Position position) {
+            this.context = context;
+            this.position = position;
+        }
+
+        @Override
+        public int compareTo(Holder other) {
+            return COMPARATOR.compare(position, other.position);
+        }
+    }
+
+    private final Timer timer = new HashedWheelTimer();
+    private final Callback callback;
+    private final long threshold;
+
+    private final Map<Long, TreeSet<Holder>> buffer = new HashMap<>();
+
+    public BufferingManager(Config config, Callback callback) {
+        this.callback = callback;
+        threshold = config.getLong(Keys.SERVER_BUFFERING_THRESHOLD);
+    }
+
+    private Timeout scheduleTimeout(Holder holder) {
+        return timer.newTimeout(
+                timeout -> {
+                    LOGGER.info("released {}", holder.position.getFixTime());
+                    buffer.get(holder.position.getDeviceId()).remove(holder);
+                    callback.onReleased(holder.context, holder.position);
+                },
+                threshold, TimeUnit.MILLISECONDS);
+    }
+
+    public void accept(ChannelHandlerContext context, Position position) {
+        if (threshold > 0) {
+            synchronized (buffer) {
+                LOGGER.info("queued {}", position.getFixTime());
+                var queue = buffer.computeIfAbsent(position.getDeviceId(), k -> new TreeSet<>());
+                Holder holder = new Holder(context, position);
+                holder.timeout = scheduleTimeout(holder);
+                queue.add(holder);
+                queue.tailSet(holder).forEach(h -> {
+                    h.timeout.cancel();
+                    h.timeout = scheduleTimeout(h);
+                });
+            }
+        } else {
+            callback.onReleased(context, position);
+        }
+    }
+
+}