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https://issues.apache.org/jira/browse/AURORA-1944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16115938#comment-16115938
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Stephan Erb commented on AURORA-1944:
-------------------------------------
On a first glance, there appear to be two problems and we should probably fix
both of them:
* When ZK is down at startup, {{CuratorServiceGroupMonitor.start}} fails with
{{Failed to begin monitoring service group.}}. The start is not re-tried in any
form but instead a shutdown is triggered.
* The scheduler shutdown fails with {{State transition from CONSTRUCTED to
STOPPED is not allowed.}}
With this patch applied, unit tests, e2e tests, and scheduler start with ZK
down seem all to work on first sight:
{code}
diff --git
a/src/main/java/org/apache/aurora/scheduler/discovery/CuratorServiceGroupMonitor.java
b/src/main/java/org/apache/aurora/scheduler/discovery/CuratorServiceGroupMonitor.java
index eba56be..4551b44 100644
---
a/src/main/java/org/apache/aurora/scheduler/discovery/CuratorServiceGroupMonitor.java
+++
b/src/main/java/org/apache/aurora/scheduler/discovery/CuratorServiceGroupMonitor.java
@@ -69,10 +69,7 @@ class CuratorServiceGroupMonitor implements
ServiceGroupMonitor {
@Override
public void start() throws MonitorException {
try {
- // NB: This blocks on an initial group population to emulate legacy
ServerSetMonitor behavior;
- // asynchronous population is an option using NORMAL or
POST_INITIALIZED_EVENT StartModes
- // though.
- groupCache.start(PathChildrenCache.StartMode.BUILD_INITIAL_CACHE);
+ groupCache.start(PathChildrenCache.StartMode.NORMAL);
} catch (Exception e) {
throw new MonitorException("Failed to begin monitoring service group.",
e);
}
{code}
[~jsirois] what do you think?
> Aurora is unable to elect leader after losing ZK for an extended period of
> time
> -------------------------------------------------------------------------------
>
> Key: AURORA-1944
> URL: https://issues.apache.org/jira/browse/AURORA-1944
> Project: Aurora
> Issue Type: Bug
> Components: Scheduler
> Environment: Running on 0.17.0
> Reporter: Renan DelValle
> Attachments: aurora-0.log, aurora-1.log, aurora-2.log
>
>
> Using Apache Curator as the Zookeeper library causes an issue where Aurora is
> unable to elect a leader if Zookeeper loses quorum for an extended period of
> time.
> Scheduler seems to crash around:
> {{W0802 14:01:14.436 [TaskEventBatchWorker, SchedulerLifecycle] Failed to
> leave leadership:
> org.apache.aurora.common.zookeeper.SingletonService$LeaveException: Failed to
> abdicate leadership of group at /aurora/scheduler}}
> When the init system brings the scheduler back up, it is unable to elect a
> leader if ZK is still down.
> Specifically, the redirect monitor fails:
> {{E0802 14:09:37.063 [RedirectMonitor STARTING,
> GuavaUtils$LifecycleShutdownListener] Service: RedirectMonitor [FAILED]
> failed unexpectedly. Triggering shutdown.}}
> Leading to every scheduler showing the following:
> {{W0802 14:16:34.646 [qtp576711849-43, LeaderRedirect] No serviceGroupMonitor
> in host set, will not redirect despite not being leader.}}
> Once the scheduler enters this state, it is unable to snap out of it until it
> is manually restarted.
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