Run pipeline in current thread if all the keys on same node

src/main/java/redis/clients/jedis/MultiNodePipelineBase.java

@@ -7,6 +7,7 @@
 import java.util.Map;
 import java.util.Queue;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
@@ -85,17 +86,27 @@ public final void sync() {
     }
     syncing = true;
 
-    ExecutorService executorService = Executors.newFixedThreadPool(MULTI_NODE_PIPELINE_SYNC_WORKERS);
+    boolean multiNode = pipelinedResponses.size() > 1;
+    Executor executor;
+    ExecutorService executorService = null;
+    if (multiNode) {
+      executorService = Executors.newFixedThreadPool(MULTI_NODE_PIPELINE_SYNC_WORKERS);
+      executor = executorService;
+    } else {
+      executor = Runnable::run;
+    }
+    CountDownLatch countDownLatch = multiNode
+        ? new CountDownLatch(pipelinedResponses.size())
+        : null;
 
-    CountDownLatch countDownLatch = new CountDownLatch(pipelinedResponses.size());
-    Iterator<Map.Entry<HostAndPort, Queue<Response<?>>>> pipelinedResponsesIterator
-        = pipelinedResponses.entrySet().iterator();
+    Iterator<Map.Entry<HostAndPort, Queue<Response<?>>>> pipelinedResponsesIterator = pipelinedResponses.entrySet()
+        .iterator();
     while (pipelinedResponsesIterator.hasNext()) {
       Map.Entry<HostAndPort, Queue<Response<?>>> entry = pipelinedResponsesIterator.next();
       HostAndPort nodeKey = entry.getKey();
       Queue<Response<?>> queue = entry.getValue();
       Connection connection = connections.get(nodeKey);
-      executorService.submit(() -> {
+      executor.execute(() -> {
         try {
           List<Object> unformatted = connection.getMany(queue.size());
           for (Object o : unformatted) {
@@ -104,22 +115,27 @@ public final void sync() {
         } catch (JedisConnectionException jce) {
           log.error("Error with connection to " + nodeKey, jce);
           // cleanup the connection
+          // TODO these operations not thread-safe and when executed here, the iter may moved
           pipelinedResponsesIterator.remove();
           connections.remove(nodeKey);
           IOUtils.closeQuietly(connection);
         } finally {
-          countDownLatch.countDown();
+          if (multiNode) {
+            countDownLatch.countDown();
+          }
         }
       });
     }
 
-    try {
-      countDownLatch.await();
-    } catch (InterruptedException e) {
-      log.error("Thread is interrupted during sync.", e);
-    }
+    if (multiNode) {
+      try {
+        countDownLatch.await();
+      } catch (InterruptedException e) {
+        log.error("Thread is interrupted during sync.", e);
+      }
 
-    executorService.shutdownNow();
+      executorService.shutdownNow();
+    }
 
     syncing = false;
   }

src/test/java/redis/clients/jedis/ClusterPipeliningTest.java

@@ -1112,6 +1112,49 @@ public void multiple() {
     }
   }
 
+  @Test
+  public void testPipelineKeysAtSameNode() {
+    try (JedisCluster cluster = new JedisCluster(nodes, DEFAULT_CLIENT_CONFIG)) {
+
+      // test simple key
+      cluster.set("foo", "bar");
+
+      try (ClusterPipeline pipeline = cluster.pipelined()) {
+        Response<String> foo = pipeline.get("foo");
+        pipeline.sync();
+
+        assertEquals("bar", foo.get());
+      }
+
+      // test multi key but at same node
+      int cnt = 3;
+      String prefix = "{foo}:";
+      for (int i = 0; i < cnt; i++) {
+        String key = prefix + i;
+        cluster.set(key, String.valueOf(i));
+      }
+
+      try (ClusterPipeline pipeline = cluster.pipelined()) {
+        List<Response<String>> results = new ArrayList<>();
+        for (int i = 0; i < cnt; i++) {
+          String key = prefix + i;
+          results.add(pipeline.get(key));
+        }
+
+        Response<Object> foo = pipeline.eval("return redis.call('get', KEYS[1])",
+            Collections.singletonList("foo"), Collections.emptyList());
+
+        pipeline.sync();
+        int idx = 0;
+        for (Response<String> res : results) {
+          assertEquals(String.valueOf(idx), res.get());
+          idx++;
+        }
+        assertEquals("bar", String.valueOf(foo.get()));
+      }
+    }
+  }
+
   private static void assertThreadsCount() {
     // Get the root thread group
     final ThreadGroup rootGroup = Thread.currentThread().getThreadGroup().getParent();