Start HashWheelTimer in ClientResources to avoid blocking calls in Ev…

…entLoop #1489

We now eagerly start HashWheelTimer when creating DefaultClientResources to avoid blocking calls originating from Timer startup on an EventLoop thread.

src/main/java/io/lettuce/core/resource/DefaultClientResources.java

@@ -232,6 +232,10 @@ protected DefaultClientResources(Builder builder) {
         reconnectDelay = builder.reconnectDelay;
         nettyCustomizer = builder.nettyCustomizer;
         tracing = builder.tracing;
+
+        if (!sharedTimer && timer instanceof HashedWheelTimer) {
+            ((HashedWheelTimer) timer).start();
+        }
     }
 
     /**

src/test/java/io/lettuce/core/resource/DefaultClientResourcesUnitTests.java

@@ -40,6 +40,8 @@
 import io.netty.util.concurrent.Future;
 
 /**
+ * Unit tests for {@link DefaultClientResources}.
+ *
  * @author Mark Paluch
  */
 class DefaultClientResourcesUnitTests {
@@ -52,6 +54,10 @@ void testDefaults() throws Exception {
         assertThat(sut.commandLatencyRecorder()).isNotNull();
         assertThat(sut.commandLatencyRecorder().isEnabled()).isTrue();
 
+        HashedWheelTimer timer = (HashedWheelTimer) sut.timer();
+
+        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 1);
+
         EventExecutorGroup eventExecutors = sut.eventExecutorGroup();
         NioEventLoopGroup eventLoopGroup = sut.eventLoopGroupProvider().allocate(NioEventLoopGroup.class);
 
@@ -222,7 +228,7 @@ void considersSharedStateFromMutation() {
         ClientResources clientResources = ClientResources.create();
         HashedWheelTimer timer = (HashedWheelTimer) clientResources.timer();
 
-        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 0);
+        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 1);
 
         ClientResources copy = clientResources.mutate().build();
         assertThat(copy.timer()).isSameAs(timer);
@@ -238,15 +244,15 @@ void considersDecoupledSharedStateFromMutation() {
         ClientResources clientResources = ClientResources.create();
         HashedWheelTimer timer = (HashedWheelTimer) clientResources.timer();
 
-        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 0);
+        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 1);
 
         ClientResources copy = clientResources.mutate().timer(new HashedWheelTimer()).build();
         HashedWheelTimer copyTimer = (HashedWheelTimer) copy.timer();
         assertThat(copy.timer()).isNotSameAs(timer);
 
         copy.shutdown().awaitUninterruptibly();
 
-        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 0);
+        assertThat(timer).hasFieldOrPropertyWithValue("workerState", 1);
         assertThat(copyTimer).hasFieldOrPropertyWithValue("workerState", 0);
 
         copyTimer.stop();