From 552299b6ecc634ea7f8168620136d6e6f4e593f8 Mon Sep 17 00:00:00 2001
From: Clint Wylie <clint.wylie@metamarkets.com>
Date: Tue, 30 Jan 2018 14:02:24 -0800
Subject: [PATCH 1/2] fix RemoteTaskRunner terminating lazy workers below
 autoscaler minNumWorkers value

---
 .../indexing/overlord/RemoteTaskRunner.java    |  3 +++
 .../overlord/RemoteTaskRunnerTest.java         | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java b/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java
index 6524a2ac8004..038f12693b22 100644
--- a/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java
+++ b/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java
@@ -1235,6 +1235,9 @@ private void taskComplete(
   @Override
   public Collection<Worker> markWorkersLazy(Predicate<ImmutableWorkerInfo> isLazyWorker, int maxWorkers)
   {
+    if (maxWorkers < 1) {
+      return Collections.emptyList();
+    }
     // status lock is used to prevent any tasks being assigned to the worker while we mark it lazy
     synchronized (statusLock) {
       Iterator<String> iterator = zkWorkers.keySet().iterator();
diff --git a/indexing-service/src/test/java/io/druid/indexing/overlord/RemoteTaskRunnerTest.java b/indexing-service/src/test/java/io/druid/indexing/overlord/RemoteTaskRunnerTest.java
index ae57a300f4f9..a681c2b88984 100644
--- a/indexing-service/src/test/java/io/druid/indexing/overlord/RemoteTaskRunnerTest.java
+++ b/indexing-service/src/test/java/io/druid/indexing/overlord/RemoteTaskRunnerTest.java
@@ -550,6 +550,24 @@ public boolean apply(ImmutableWorkerInfo input)
     Assert.assertEquals(1, remoteTaskRunner.getLazyWorkers().size());
   }
 
+  @Test
+  public void testFindLazyWorkerNotRunningAnyTaskButWithZeroMaxWorkers() throws Exception
+  {
+    doSetup();
+    Collection<Worker> lazyworkers = remoteTaskRunner.markWorkersLazy(
+        new Predicate<ImmutableWorkerInfo>()
+        {
+          @Override
+          public boolean apply(ImmutableWorkerInfo input)
+          {
+            return true;
+          }
+        }, 0
+    );
+    Assert.assertEquals(0, lazyworkers.size());
+    Assert.assertEquals(0, remoteTaskRunner.getLazyWorkers().size());
+  }
+
   @Test
   public void testWorkerZKReconnect() throws Exception
   {

From 3a1099ef73c5daed79cad339ed73f03bc8b81eb4 Mon Sep 17 00:00:00 2001
From: Clint Wylie <clint.wylie@metamarkets.com>
Date: Wed, 31 Jan 2018 15:09:43 -0800
Subject: [PATCH 2/2] add comment

---
 .../main/java/io/druid/indexing/overlord/RemoteTaskRunner.java  | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java b/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java
index 038f12693b22..e9e623cc8016 100644
--- a/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java
+++ b/indexing-service/src/main/java/io/druid/indexing/overlord/RemoteTaskRunner.java
@@ -1235,6 +1235,8 @@ private void taskComplete(
   @Override
   public Collection<Worker> markWorkersLazy(Predicate<ImmutableWorkerInfo> isLazyWorker, int maxWorkers)
   {
+    // skip the lock and bail early if we should not mark any workers lazy (e.g. number
+    // of current workers is at or below the minNumWorkers of autoscaler config)
     if (maxWorkers < 1) {
       return Collections.emptyList();
     }