POOL-356 fix deadlock on massive concurrent requests Happens when blockWhenExhausted is active. The idleObjects.takeFirst and .pollFirst operations perform a lock. So if the pool is empty and the MaxTotal is hit we end up having multiple Threads perform a lock internally via idleObjects.takeFirst().
But if a condition occurs to destroy the object instead of putting it back into the pool then nobody notifies the Lock Condition. The proposed solution will simply create a new object in that case and puts it back into the idle queue IF there are active threads waiting for some idle objects. Project: http://git-wip-us.apache.org/repos/asf/commons-pool/repo Commit: http://git-wip-us.apache.org/repos/asf/commons-pool/commit/016a1f67 Tree: http://git-wip-us.apache.org/repos/asf/commons-pool/tree/016a1f67 Diff: http://git-wip-us.apache.org/repos/asf/commons-pool/diff/016a1f67 Branch: refs/heads/master Commit: 016a1f67263fe1cde1d910dc7002d972811951c5 Parents: 60a041d Author: Mark Struberg <strub...@apache.org> Authored: Wed Oct 24 21:23:20 2018 +0200 Committer: Mark Struberg <strub...@apache.org> Committed: Wed Oct 24 21:23:20 2018 +0200 ---------------------------------------------------------------------- .../org/apache/commons/pool2/impl/GenericObjectPool.java | 9 +++++++++ .../apache/commons/pool2/impl/TestGenericObjectPool.java | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/commons-pool/blob/016a1f67/src/main/java/org/apache/commons/pool2/impl/GenericObjectPool.java ---------------------------------------------------------------------- diff --git a/src/main/java/org/apache/commons/pool2/impl/GenericObjectPool.java b/src/main/java/org/apache/commons/pool2/impl/GenericObjectPool.java index abdf7e1..0575f7e 100644 --- a/src/main/java/org/apache/commons/pool2/impl/GenericObjectPool.java +++ b/src/main/java/org/apache/commons/pool2/impl/GenericObjectPool.java @@ -914,6 +914,15 @@ public class GenericObjectPool<T> extends BaseGenericObjectPool<T> destroyedCount.incrementAndGet(); createCount.decrementAndGet(); } + + if (idleObjects.isEmpty() && idleObjects.hasTakeWaiters()) { + // POOL-356. + // In case there are already threads waiting on something in the pool + // (e.g. idleObjects.takeFirst(); then we need to provide them a fresh instance. + // Otherwise they will be stuck forever (or until timeout) + PooledObject<T> freshPooled = create(); + idleObjects.put(freshPooled); + } } @Override http://git-wip-us.apache.org/repos/asf/commons-pool/blob/016a1f67/src/test/java/org/apache/commons/pool2/impl/TestGenericObjectPool.java ---------------------------------------------------------------------- diff --git a/src/test/java/org/apache/commons/pool2/impl/TestGenericObjectPool.java b/src/test/java/org/apache/commons/pool2/impl/TestGenericObjectPool.java index 3e897f7..fd5a871 100644 --- a/src/test/java/org/apache/commons/pool2/impl/TestGenericObjectPool.java +++ b/src/test/java/org/apache/commons/pool2/impl/TestGenericObjectPool.java @@ -777,7 +777,7 @@ public class TestGenericObjectPool extends TestBaseObjectPool { } // Give the threads a chance to start doing some work try { - Thread.sleep(5000); + Thread.sleep(100); } catch(final InterruptedException e) { // ignored } @@ -824,6 +824,7 @@ public class TestGenericObjectPool extends TestBaseObjectPool { } } if(threads[i].failed()) { + threads[i]._error.printStackTrace(); fail("Thread "+i+" failed: "+threads[i]._error.toString()); } }
