nmode's Git Repositories - signal-cli/blob - lib/src/main/java/org/asamk/signal/manager/internal/SignalWebSocketHealthMonitor.java

   1 package org.asamk.signal.manager.internal;
   2
   3 import org.slf4j.Logger;
   4 import org.slf4j.LoggerFactory;
   5 import org.whispersystems.signalservice.api.util.Preconditions;
   6 import org.whispersystems.signalservice.api.util.SleepTimer;
   7 import org.whispersystems.signalservice.api.websocket.HealthMonitor;
   8 import org.whispersystems.signalservice.api.websocket.SignalWebSocket;
   9 import org.whispersystems.signalservice.api.websocket.WebSocketConnectionState;
  10 import org.whispersystems.signalservice.internal.websocket.OkHttpWebSocketConnection;
  11
  12 import java.util.concurrent.Executor;
  13 import java.util.concurrent.Executors;
  14 import java.util.concurrent.TimeUnit;
  15
  16 import io.reactivex.rxjava3.schedulers.Schedulers;
  17 import kotlin.Unit;
  18
  19 final class SignalWebSocketHealthMonitor implements HealthMonitor {
  20
  21     private static final Logger logger = LoggerFactory.getLogger(SignalWebSocketHealthMonitor.class);
  22
  23     /**
  24      * This is the amount of time in between sent keep alives. Must be greater than [KEEP_ALIVE_TIMEOUT]
  25      */
  26     private static final long KEEP_ALIVE_SEND_CADENCE = TimeUnit.SECONDS.toMillis(OkHttpWebSocketConnection.KEEPALIVE_FREQUENCY_SECONDS);
  27
  28     /**
  29      * This is the amount of time we will wait for a response to the keep alive before we consider the websockets dead.
  30      * It is required that this value be less than [KEEP_ALIVE_SEND_CADENCE]
  31      */
  32     private static final long KEEP_ALIVE_TIMEOUT = TimeUnit.SECONDS.toMillis(20);
  33
  34     private final Executor executor = Executors.newSingleThreadExecutor();
  35     private final SleepTimer sleepTimer;
  36     private SignalWebSocket webSocket = null;
  37     private volatile KeepAliveSender keepAliveSender = null;
  38     private boolean needsKeepAlive = false;
  39     private long lastKeepAliveReceived = 0;
  40
  41     public SignalWebSocketHealthMonitor(SleepTimer sleepTimer) {
  42         this.sleepTimer = sleepTimer;
  43     }
  44
  45     void monitor(SignalWebSocket webSocket) {
  46         Preconditions.checkNotNull(webSocket);
  47         Preconditions.checkArgument(this.webSocket == null, "monitor can only be called once");
  48
  49         executor.execute(() -> {
  50
  51             this.webSocket = webSocket;
  52
  53             webSocket.getState()
  54                     .subscribeOn(Schedulers.computation())
  55                     .observeOn(Schedulers.computation())
  56                     .distinctUntilChanged()
  57                     .subscribe(this::onStateChanged);
  58
  59             webSocket.setKeepAliveChangedListener(this::updateKeepAliveSenderStatus);
  60         });
  61     }
  62
  63     private void onStateChanged(WebSocketConnectionState connectionState) {
  64         executor.execute(() -> {
  65             needsKeepAlive = connectionState == WebSocketConnectionState.CONNECTED;
  66
  67             updateKeepAliveSenderStatus();
  68         });
  69     }
  70
  71     @Override
  72     public void onKeepAliveResponse(long sentTimestamp, boolean isIdentifiedWebSocket) {
  73         final var keepAliveTime = System.currentTimeMillis();
  74         executor.execute(() -> lastKeepAliveReceived = keepAliveTime);
  75     }
  76
  77     @Override
  78     public void onMessageError(int status, boolean isIdentifiedWebSocket) {
  79     }
  80
  81     private Unit updateKeepAliveSenderStatus() {
  82         if (keepAliveSender == null && sendKeepAlives()) {
  83             keepAliveSender = new KeepAliveSender();
  84             keepAliveSender.start();
  85         } else if (keepAliveSender != null && !sendKeepAlives()) {
  86             keepAliveSender.shutdown();
  87             keepAliveSender = null;
  88         }
  89         return Unit.INSTANCE;
  90     }
  91
  92     private boolean sendKeepAlives() {
  93         return needsKeepAlive && webSocket != null && webSocket.getShouldSendKeepAlives();
  94     }
  95
  96     /**
  97      * Sends periodic heartbeats/keep-alives over the WebSocket to prevent connection timeouts. If
  98      * the WebSocket fails to get a return heartbeat after [KEEP_ALIVE_TIMEOUT] seconds, it is forced to be recreated.
  99      */
 100     private final class KeepAliveSender extends Thread {
 101
 102         private volatile boolean shouldKeepRunning = true;
 103
 104         @Override
 105         public void run() {
 106             logger.debug("[KeepAliveSender({})] started", this.threadId());
 107             lastKeepAliveReceived = System.currentTimeMillis();
 108
 109             var keepAliveSendTime = System.currentTimeMillis();
 110             while (shouldKeepRunning && sendKeepAlives()) {
 111                 try {
 112                     final var nextKeepAliveSendTime = keepAliveSendTime + KEEP_ALIVE_SEND_CADENCE;
 113                     sleepUntil(nextKeepAliveSendTime);
 114
 115                     if (shouldKeepRunning && sendKeepAlives()) {
 116                         keepAliveSendTime = System.currentTimeMillis();
 117                         webSocket.sendKeepAlive();
 118                     }
 119
 120                     final var responseRequiredTime = keepAliveSendTime + KEEP_ALIVE_TIMEOUT;
 121                     sleepUntil(responseRequiredTime);
 122
 123                     if (shouldKeepRunning && sendKeepAlives()) {
 124                         if (lastKeepAliveReceived < keepAliveSendTime) {
 125                             logger.debug("Missed keep alive, last: {} needed by: {}",
 126                                     lastKeepAliveReceived,
 127                                     responseRequiredTime);
 128                             webSocket.forceNewWebSocket();
 129                         }
 130                     }
 131                 } catch (Throwable e) {
 132                     logger.warn("Keep alive sender failed", e);
 133                 }
 134             }
 135             logger.debug("[KeepAliveSender({})] ended", threadId());
 136         }
 137
 138         void sleepUntil(long timeMillis) {
 139             while (System.currentTimeMillis() < timeMillis) {
 140                 final var waitTime = timeMillis - System.currentTimeMillis();
 141                 if (waitTime > 0) {
 142                     try {
 143                         sleepTimer.sleep(waitTime);
 144                     } catch (InterruptedException e) {
 145                         logger.warn("WebSocket health monitor interrupted", e);
 146                     }
 147                 }
 148             }
 149         }
 150
 151         void shutdown() {
 152             shouldKeepRunning = false;
 153         }
 154     }
 155 }
 156