[jira] [Commented] (CLOUDSTACK-10310) KVM hosts reboot if there is a short transient storage error

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CLOUDSTACK-10310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16641913#comment-16641913 ] 

ASF GitHub Bot commented on CLOUDSTACK-10310:
---------------------------------------------

csquire commented on issue #2722: CLOUDSTACK-10310 Fix KVM reboot on storage issue
URL: https://github.com/apache/cloudstack/pull/2722#issuecomment-427859929
 
 
   This PR doesn't seem to completely fix the reboot problem. We installed the RC release with this PR on a test system and are still able to get the KVM host to reboot by using iptables to drop outgoing requests to NFS. My investigation shows that the line [`storage = conn.storagePoolLookupByUUIDString(uuid);`](https://github.com/apache/cloudstack/blob/4.11/plugins/hypervisors/kvm/src/com/cloud/hypervisor/kvm/resource/KVMHAMonitor.java#L95) blocks indefinitely.  So, `kvmheartbeat.sh` is never executed, a host investigation is started, the host with blocked NFS is marked as `Down` and finally all VMs on that host are rescheduled and result in duplicate VMs.
   
   I pulled a thread dump and found the KVMHAMonitor thread will hang here until NFS is unblocked, didn't dig any deeper yet though.
   
   ```"Thread-20" - Thread t@135
      java.lang.Thread.State: RUNNABLE
           at com.sun.jna.Native.invokePointer(Native Method)
           at com.sun.jna.Function.invokePointer(Function.java:470)
           at com.sun.jna.Function.invoke(Function.java:404)
           at com.sun.jna.Function.invoke(Function.java:315)
           at com.sun.jna.Library$Handler.invoke(Library.java:212)
           at com.sun.proxy.$Proxy3.virStoragePoolLookupByUUIDString(Unknown Source)
           at org.libvirt.Connect.storagePoolLookupByUUIDString(Unknown Source)
           at com.cloud.hypervisor.kvm.resource.KVMHAMonitor$Monitor.runInContext(KVMHAMonitor.java:95)
           - locked <1afb3370> (a java.util.concurrent.ConcurrentHashMap)
           at org.apache.cloudstack.managed.context.ManagedContextRunnable$1.run(ManagedContextRunnable.java:49)
           at org.apache.cloudstack.managed.context.impl.DefaultManagedContext$1.call(DefaultManagedContext.java:56)
           at org.apache.cloudstack.managed.context.impl.DefaultManagedContext.callWithContext(DefaultManagedContext.java:103)
           at org.apache.cloudstack.managed.context.impl.DefaultManagedContext.runWithContext(DefaultManagedContext.java:53)
           at org.apache.cloudstack.managed.context.ManagedContextRunnable.run(ManagedContextRunnable.java:46)
           at java.lang.Thread.run(Thread.java:748)
   
      Locked ownable synchronizers:
           - None```

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> KVM hosts reboot if there is a short transient storage error
> ------------------------------------------------------------
>
>                 Key: CLOUDSTACK-10310
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-10310
>             Project: CloudStack
>          Issue Type: Improvement
>      Security Level: Public(Anyone can view this level - this is the default.) 
>          Components: KVM
>    Affects Versions: 4.9.0, 4.10.0.0
>            Reporter: Sean Lair
>            Priority: Major
>
> If the KVM heartbeat file can't be written to, the host is rebooted, and thus taking down all VMs running on it.  The code does try 5x times before the reboot, but the there is not a delay between the retires, so they are 5 simultaneous retries, which doesn't help.  Standard SAN storage HA operations or quick network blip could cause this reboot to occur.
> Some discussions on the dev mailing list revealed that some people are just commenting out the reboot line in their version of the CloudStack source.
> A better option (and a new PR is being issued) would be have it sleep between tries so it isn't 5x almost simultaneous tries.  Plus, instead of rebooting, the cloudstack-agent could just be stopped on the host instead.  This will cause alerts to be issued and if the host is disconnected long-enough, depending on the HA code in use, VM HA could handle the host failure.
> The built-in reboot of the host seemed drastic



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