make number of keepAlives configurable

client/src/main/java/io/atomix/copycat/client/CopycatClient.java

@@ -560,6 +560,7 @@ final class Builder implements io.atomix.catalyst.util.Builder<CopycatClient> {
     private Serializer serializer;
     private Duration sessionTimeout = Duration.ZERO;
     private Duration unstabilityTimeout = Duration.ZERO;
+    private int keepAlivesPerTimeoutInterval = 2;
     private ConnectionStrategy connectionStrategy = ConnectionStrategies.ONCE;
     private ServerSelectionStrategy serverSelectionStrategy = ServerSelectionStrategies.ANY;
     private RecoveryStrategy recoveryStrategy = RecoveryStrategies.CLOSE;
@@ -623,6 +624,19 @@ public Builder withSessionTimeout(Duration sessionTimeout) {
       return this;
     }
 
+    /**
+     * Sets the number of keep-alives to send during a session timeout interval. Default value is 2.
+     *
+     * @param keepAlivesPerTimeoutInterval The number of keep-alives to send during a session timeout interval
+     * @return The client builder.
+     * @throws IllegalArgumentException if the keepAlivesPerTimeoutInterval is not positive
+     */
+    public Builder withKeepAlivesPerTimeoutInterval(int keepAlivesPerTimeoutInterval) {
+      Assert.arg(keepAlivesPerTimeoutInterval > 0, "keepAlivesPerTimeoutInterval must be positive");
+      this.keepAlivesPerTimeoutInterval = keepAlivesPerTimeoutInterval;
+      return this;
+    }
+
     /**
      * Sets the timeout for session unstability. Client is automatically closed if it can not reach servers within
      * the given timeout.
@@ -711,7 +725,8 @@ public CopycatClient build() {
         connectionStrategy,
         recoveryStrategy,
         sessionTimeout,
-        unstabilityTimeout
+        unstabilityTimeout,
+        keepAlivesPerTimeoutInterval
       );
     }
   }

client/src/main/java/io/atomix/copycat/client/DefaultCopycatClient.java

@@ -57,6 +57,7 @@ public class DefaultCopycatClient implements CopycatClient {
   private final AddressSelector selector;
   private final Duration sessionTimeout;
   private final Duration unstabilityTimeout;
+  private final int keepAlivesPerTimeoutInterval;
   private final ConnectionStrategy connectionStrategy;
   private final RecoveryStrategy recoveryStrategy;
   private ClientSession session;
@@ -68,7 +69,10 @@ public class DefaultCopycatClient implements CopycatClient {
   private final Set<EventListener<?>> eventListeners = new CopyOnWriteArraySet<>();
   private Listener<Session.State> changeListener;
 
-  DefaultCopycatClient(String clientId, Collection<Address> cluster, Transport transport, ThreadContext ioContext, ThreadContext eventContext, ServerSelectionStrategy selectionStrategy, ConnectionStrategy connectionStrategy, RecoveryStrategy recoveryStrategy, Duration sessionTimeout, Duration unstabilityTimeout) {
+  DefaultCopycatClient(String clientId, Collection<Address> cluster, Transport transport, ThreadContext ioContext,
+                       ThreadContext eventContext, ServerSelectionStrategy selectionStrategy, ConnectionStrategy
+                           connectionStrategy, RecoveryStrategy recoveryStrategy, Duration sessionTimeout, Duration
+                           unstabilityTimeout, int keepAlivesPerTimeoutInterval) {
     this.clientId = Assert.notNull(clientId, "clientId");
     this.cluster = Assert.notNull(cluster, "cluster");
     this.transport = Assert.notNull(transport, "transport");
@@ -78,7 +82,8 @@ public class DefaultCopycatClient implements CopycatClient {
     this.connectionStrategy = Assert.notNull(connectionStrategy, "connectionStrategy");
     this.recoveryStrategy = Assert.notNull(recoveryStrategy, "recoveryStrategy");
     this.sessionTimeout = Assert.notNull(sessionTimeout, "sessionTimeout");
-    this.unstabilityTimeout = Assert.notNull(unstabilityTimeout, "unstabilityTimeout");;
+    this.unstabilityTimeout = Assert.notNull(unstabilityTimeout, "unstabilityTimeout");
+    this.keepAlivesPerTimeoutInterval = keepAlivesPerTimeoutInterval;
   }
 
   @Override
@@ -128,7 +133,7 @@ public ThreadContext context() {
    */
   private ClientSession newSession() {
     ClientSession session = new ClientSession(clientId, transport.client(), selector, ioContext, connectionStrategy, sessionTimeout,
-                                              unstabilityTimeout
+                                              unstabilityTimeout, keepAlivesPerTimeoutInterval
     );
 
     // Update the session change listener.

client/src/main/java/io/atomix/copycat/client/session/ClientSession.java

@@ -59,14 +59,14 @@ public class ClientSession implements Session {
   private final ClientSessionListener listener;
   private final ClientSessionSubmitter submitter;
 
-  public ClientSession(String id, Client client, AddressSelector selector, ThreadContext context, ConnectionStrategy connectionStrategy, Duration sessionTimeout, Duration unstabilityTimeout) {
-    this(new ClientConnection(id, client, selector), new ClientSessionState(id, unstabilityTimeout), context, connectionStrategy, sessionTimeout);
+  public ClientSession(String id, Client client, AddressSelector selector, ThreadContext context, ConnectionStrategy connectionStrategy, Duration sessionTimeout, Duration unstabilityTimeout, int keepalivesPerTimeoutInterval) {
+    this(new ClientConnection(id, client, selector), new ClientSessionState(id, unstabilityTimeout), context, connectionStrategy, sessionTimeout, keepalivesPerTimeoutInterval);
   }
 
-  private ClientSession(ClientConnection connection, ClientSessionState state, ThreadContext context, ConnectionStrategy connectionStrategy, Duration sessionTimeout) {
+  private ClientSession(ClientConnection connection, ClientSessionState state, ThreadContext context, ConnectionStrategy connectionStrategy, Duration sessionTimeout, int keepalivesPerTimeoutInterval) {
     this.connection = Assert.notNull(connection, "connection");
     this.state = Assert.notNull(state, "state");
-    this.manager = new ClientSessionManager(connection, state, context, connectionStrategy, sessionTimeout);
+    this.manager = new ClientSessionManager(connection, state, context, connectionStrategy, sessionTimeout, keepalivesPerTimeoutInterval);
     ClientSequencer sequencer = new ClientSequencer(state);
     this.listener = new ClientSessionListener(connection, state, sequencer, context);
     this.submitter = new ClientSessionSubmitter(connection, state, sequencer, context);

client/src/main/java/io/atomix/copycat/client/session/ClientSessionManager.java

@@ -40,15 +40,17 @@ final class ClientSessionManager {
   private final ThreadContext context;
   private final ConnectionStrategy strategy;
   private final Duration sessionTimeout;
+  private final int keepAlivesPerTimeoutInterval;
   private Duration interval;
   private Scheduled keepAlive;
 
-  ClientSessionManager(ClientConnection connection, ClientSessionState state, ThreadContext context, ConnectionStrategy connectionStrategy, Duration sessionTimeout) {
+  ClientSessionManager(ClientConnection connection, ClientSessionState state, ThreadContext context, ConnectionStrategy connectionStrategy, Duration sessionTimeout, int keepAlivesPerTimeoutInterval) {
     this.connection = Assert.notNull(connection, "connection");
     this.state = Assert.notNull(state, "state");
     this.context = Assert.notNull(context, "context");
     this.strategy = Assert.notNull(connectionStrategy, "connectionStrategy");
     this.sessionTimeout = Assert.notNull(sessionTimeout, "sessionTimeout");
+    this.keepAlivesPerTimeoutInterval = Assert.arg(keepAlivesPerTimeoutInterval, keepAlivesPerTimeoutInterval > 0, "keepAlivesPerTimeoutInterval");
   }
 
   /**
@@ -94,7 +96,7 @@ private void register(RegisterAttempt attempt) {
       if (error == null) {
         state.getLogger().trace("Received {}", response);
         if (response.status() == Response.Status.OK) {
-          interval = Duration.ofMillis(response.timeout()).dividedBy(2);
+          interval = Duration.ofMillis(response.timeout()).dividedBy(keepAlivesPerTimeoutInterval);
           connection.reset(response.leader(), response.members());
           state.setSessionId(response.session())
             .setState(Session.State.OPEN);

client/src/test/java/io/atomix/copycat/client/session/ClientSessionManagerTest.java

@@ -73,7 +73,7 @@ public void testSessionRegisterUnregister() throws Throwable {
     Executor executor = new MockExecutor();
     when(context.executor()).thenReturn(executor);
 
-    ClientSessionManager manager = new ClientSessionManager(connection, state, context, ConnectionStrategies.EXPONENTIAL_BACKOFF, Duration.ZERO);
+    ClientSessionManager manager = new ClientSessionManager(connection, state, context, ConnectionStrategies.EXPONENTIAL_BACKOFF, Duration.ZERO, 2);
     manager.open().join();
 
     assertEquals(state.getSessionId(), 1);