close session when it's not responding for a while (#32)

src/main/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSession.java

@@ -24,6 +24,7 @@
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * Created by weijiesun on 17-9-13.
@@ -62,6 +63,8 @@ public void initChannel(SocketChannel ch) {
                         pipeline.addLast("ClientHandler", new ReplicaSession.DefaultHandler());
                     }
                 });
+
+        this.firstRecentTimedOutMs = new AtomicLong(0);
     }
 
     // You can specify a message response filter with constructor or with "setMessageResponseFilter" function.
@@ -71,6 +74,7 @@ public ReplicaSession(rpc_address address, EventLoopGroup rpcGroup, int socketTi
         this(address, rpcGroup, socketTimeout);
         this.filter = filter;
     }
+
     public void setMessageResponseFilter(MessageResponseFilter filter) {
         this.filter = filter;
     }
@@ -220,8 +224,25 @@ private void tryNotifyWithSequenceID(
                 entry.timeoutTask.cancel(true);
             entry.op.rpc_error.errno = errno;
             entry.callback.run();
-        }
-        else {
+
+            if (errno == error_types.ERR_TIMEOUT) {
+                long firstTs = firstRecentTimedOutMs.get();
+                if (firstTs == 0) {
+                    // it is the first timeout in the window.
+                    firstRecentTimedOutMs.set(System.currentTimeMillis());
+                } else if (System.currentTimeMillis() - firstTs >= sessionResetTimeWindowMs) {
+                    // ensure that closeSession() will be invoked only once.
+                    if (firstRecentTimedOutMs.compareAndSet(firstTs, 0)) {
+                        logger.warn("{}: actively close the session because it's not responding for {} seconds",
+                                name(),
+                                sessionResetTimeWindowMs / 1000);
+                        closeSession();
+                    }
+                }
+            } else {
+                firstRecentTimedOutMs.set(0);
+            }
+        } else {
             logger.warn("{}: {} is removed by others, current error {}, isTimeoutTask {}",
                     name(), seqID, errno.toString(), isTimeoutTask);
         }
@@ -305,11 +326,19 @@ private final static class VolatileFields {
         public ConnState state = ConnState.DISCONNECTED;
         public Channel nettyChannel = null;
     }
+
     private volatile VolatileFields fields = new VolatileFields();
 
-    private rpc_address address;
+    private final rpc_address address;
     private Bootstrap boot;
     private EventLoopGroup rpcGroup;
 
+    // Session will be actively closed if all the rpcs across `sessionResetTimeWindowMs`
+    // are timed out, in that case we suspect that the server is unavailable.
+
+    // Timestamp of the first timed out rpc.
+    private AtomicLong firstRecentTimedOutMs;
+    private static final long sessionResetTimeWindowMs = 10 * 1000; // 10s
+
     private static final Logger logger = org.slf4j.LoggerFactory.getLogger(ReplicaSession.class);
 }