# Zombie Node

**URL:** <https://forums.percona.com/t/zombie-node/4331>\
**Category:** Percona XtraDB Cluster 5.x\
**Created:** [August 3, 2015, 7:23pm UTC](https://forums.percona.com/t/zombie-node/4331 "2015-08-03T19:23:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dazza76](https://avatars.discourse-cdn.com/v4/letter/d/eb8c5e/32.png) [@dazza76](https://forums.percona.com/u/dazza76)\
**Post date:** [August 3, 2015, 7:23pm UTC](https://forums.percona.com/t/zombie-node/4331/1 "2015-08-03T19:23:06Z")

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I have a 6 node cluster that was running well ,  
Unfortunately the other day one of the servers had a lockup , still pingable but not reachable ,  
Until I killed the node the entire cluster was locked and was unable to make any queries ,  
Version I am using is Percona-XtraDB-Cluster 56-5.6.22-25.8.978  
once the Node was disabled the services retuned to normal

Has anybody experienced this before and a possible solution to stop it happening again .

Regards

Darren

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**Author:** ![przemek](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/przemek/32/3_2.png) [@przemek](https://forums.percona.com/u/przemek)\
**Post date:** [September 8, 2015, 7:06am UTC](https://forums.percona.com/t/zombie-node/4331/2 "2015-09-08T07:06:31Z")

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By ‘unable to make any queries’ do you mean SELECTs too?  
If one node is locked in a cluster, which means it’s still a valid member, has communication to other nodes working, but for some reason it is unable to apply writes, a Flow Control mechanism will fire up, which eventually will pause writes on all other nodes. This is in order to prevent too much replication lag in a cluster. See more details here:  
[url][https://www.percona.com/blog/2013/05/02/galera-flow-control-in-percona-xtradb-cluster-for-mysql/[/url]](https://www.percona.com/blog/2013/05/02/galera-flow-control-in-percona-xtradb-cluster-for-mysql/%5B/url%5D)