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java/org/apache/tomcat/websocket/server/WsWriteTimeout.java

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+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one or more
+ *  contributor license agreements.  See the NOTICE file distributed with
+ *  this work for additional information regarding copyright ownership.
+ *  The ASF licenses this file to You 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.apache.tomcat.websocket.server;
+
+import java.util.Comparator;
+import java.util.Set;
+import java.util.concurrent.ConcurrentSkipListSet;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.apache.tomcat.websocket.BackgroundProcess;
+import org.apache.tomcat.websocket.BackgroundProcessManager;
+
+/**
+ * Provides timeouts for asynchronous web socket writes. On the server side we
+ * only have access to {@link javax.servlet.ServletOutputStream} and
+ * {@link javax.servlet.ServletInputStream} so there is no way to set a timeout
+ * for writes to the client.
+ */
+public class WsWriteTimeout implements BackgroundProcess {
+
+    private final Set<WsRemoteEndpointImplServer> endpoints =
+            new ConcurrentSkipListSet<>(new EndpointComparator());
+    private final AtomicInteger count = new AtomicInteger(0);
+    private int backgroundProcessCount = 0;
+    private volatile int processPeriod = 1;
+
+    @Override
+    public void backgroundProcess() {
+        // This method gets called once a second.
+        backgroundProcessCount ++;
+
+        if (backgroundProcessCount >= processPeriod) {
+            backgroundProcessCount = 0;
+
+            long now = System.currentTimeMillis();
+            for (WsRemoteEndpointImplServer endpoint : endpoints) {
+                if (endpoint.getTimeoutExpiry() < now) {
+                    // Background thread, not the thread that triggered the
+                    // write so no need to use a dispatch
+                    endpoint.onTimeout(false);
+                } else {
+                    // Endpoints are ordered by timeout expiry so if this point
+                    // is reached there is no need to check the remaining
+                    // endpoints
+                    break;
+                }
+            }
+        }
+    }
+
+
+    @Override
+    public void setProcessPeriod(int period) {
+        this.processPeriod = period;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     *
+     * The default value is 1 which means asynchronous write timeouts are
+     * processed every 1 second.
+     */
+    @Override
+    public int getProcessPeriod() {
+        return processPeriod;
+    }
+
+
+    public void register(WsRemoteEndpointImplServer endpoint) {
+        boolean result = endpoints.add(endpoint);
+        if (result) {
+            int newCount = count.incrementAndGet();
+            if (newCount == 1) {
+                BackgroundProcessManager.getInstance().register(this);
+            }
+        }
+    }
+
+
+    public void unregister(WsRemoteEndpointImplServer endpoint) {
+        boolean result = endpoints.remove(endpoint);
+        if (result) {
+            int newCount = count.decrementAndGet();
+            if (newCount == 0) {
+                BackgroundProcessManager.getInstance().unregister(this);
+            }
+        }
+    }
+
+
+    /**
+     * Note: this comparator imposes orderings that are inconsistent with equals
+     */
+    private static class EndpointComparator implements
+            Comparator<WsRemoteEndpointImplServer> {
+
+        @Override
+        public int compare(WsRemoteEndpointImplServer o1,
+                WsRemoteEndpointImplServer o2) {
+
+            long t1 = o1.getTimeoutExpiry();
+            long t2 = o2.getTimeoutExpiry();
+
+            if (t1 < t2) {
+                return -1;
+            } else if (t1 == t2) {
+                return 0;
+            } else {
+                return 1;
+            }
+        }
+    }
+}