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https://issues.apache.org/jira/browse/SOLR-5945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16902148#comment-16902148
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Endika Posadas edited comment on SOLR-5945 at 8/7/19 3:16 PM:
--------------------------------------------------------------
There are circumstances when retrying makes sense. E.g.: the whole environment
goes down, including the DNS. If Solr comes back up before the DNS is up and
running, it will fall into this UnknownHostException and go into an invalid
state. However, if it keeps retrying, it will eventually come back alive when
the DNS is back.
I have attached a patch for Solr 6.6 that will retry to connect based on a
timeout.
was (Author: enpos):
There are circumstances when retrying makes sense. E.g.: the whole environment
goes down, including the DNS. If Solr comes back up before the DNS is up and
running, it will fall into this UnknownHostException and go into an invalid
state. However, if it keeps retrying, it will eventually come back alive when
the DNS is back.
I have attached a patch that will retry to connect based on a timeout.
> Add retry for zookeeper reconnect failure
> -----------------------------------------
>
> Key: SOLR-5945
> URL: https://issues.apache.org/jira/browse/SOLR-5945
> Project: Solr
> Issue Type: Improvement
> Components: SolrCloud
> Affects Versions: 4.7
> Reporter: Jessica Cheng Mallet
> Priority: Major
> Labels: solrcloud, zookeeper
> Attachments: solr_6_6-5945.patch
>
>
> We had some network issue where we temporarily lost connection and DNS. The
> zookeeper client properly triggered the watcher. However, when trying to
> reconnect, this following Exception is thrown:
> 2014-03-27 17:24:46,882 ERROR [main-EventThread] SolrException.java (line
> 121) :java.net.UnknownHostException: <host name (scrubbed)>: Name or service
> not known
> at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
> at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:866)
> at
> java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1258)
> at java.net.InetAddress.getAllByName0(InetAddress.java:1211)
> at java.net.InetAddress.getAllByName(InetAddress.java:1127)
> at java.net.InetAddress.getAllByName(InetAddress.java:1063)
> at
> org.apache.zookeeper.client.StaticHostProvider.<init>(StaticHostProvider.java:60)
> at org.apache.zookeeper.ZooKeeper.<init>(ZooKeeper.java:445)
> at org.apache.zookeeper.ZooKeeper.<init>(ZooKeeper.java:380)
> at
> org.apache.solr.common.cloud.SolrZooKeeper.<init>(SolrZooKeeper.java:41)
> at
> org.apache.solr.common.cloud.DefaultConnectionStrategy.reconnect(DefaultConnectionStrategy.java:53)
> at
> org.apache.solr.common.cloud.ConnectionManager.process(ConnectionManager.java:147)
> at
> org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
> at
> org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)
> I tried to look at the code and it seems that there'd be no further retries
> to connect to Zookeeper, and the node is basically left in a bad state and
> will not recover on its own. (Please correct me if I'm reading this wrong.)
> Thinking about it, this is probably fair, since normally you wouldn't expect
> retries to fix an "unknown host" issue (even though in our case it would
> have) but I'm wondering what we should do to handle this situation if it
> happens again in the future.
> Any advice is appreciated.
> From Mark Miller:
> We don’t currently retry, but I don’t think it would hurt much if we did - at
> least briefly.
> If you want to file a JIRA issue, that would be the best way to get it in a
> future release.
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