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https://issues.apache.org/jira/browse/SOLR-13899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16968388#comment-16968388
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Erick Erickson commented on SOLR-13899:
---------------------------------------
Thanks for raising this, and _especially_ for providing such detailed analysis!
I won't be able to get to this either, but thought an "good job" was in order ;)
> zkstatus page incorrectly reports zookeeper in error when Zookeeper observers
> are present
> -----------------------------------------------------------------------------------------
>
> Key: SOLR-13899
> URL: https://issues.apache.org/jira/browse/SOLR-13899
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Components: SolrCloud
> Affects Versions: 8.3.0
> Reporter: Salvatore
> Priority: Trivial
> Labels: easyfix
> Attachments: zkstatus.png
>
>
> When a zookeeper ensemble has 'observers', the zkstatus page incorrectly says
> Zookeeper status is in error (See attachment.)
> This is because the
> [ZookeeperStatusHandler|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/handler/admin/ZookeeperStatusHandler.java]
> does not account for the
> '[observer|https://zookeeper.apache.org/doc/current/zookeeperObservers.html]'
> role whatsoever.
> This should be an easy fix - I see there being two options;
> 1. Treat observers as followers by changing
> [L112|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/handler/admin/ZookeeperStatusHandler.java#L112]
> to
> {code:java}
> if ("follower".equals(state) || "observer".equals(state)) {
> {code}
>
> 2. Ignore observers from the required follower count by changing
> [L116|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/handler/admin/ZookeeperStatusHandler.java#L116]
> to
> {code:java}
> reportedFollowers =
> Integer.parseInt(String.valueOf(stat.get("zk_synced_followers")));
> {code}
> Option 1 will make the zkstatus page show error when an observer is down.
> Option 2 will not make the zkstatus page show error when an observer is down.
> *Ideally*, additional logic to account for observers should be added, and
> show a STATUS_YELLOW when any observers are down (but followers are all up),
> as this means the ensemble is only in a degraded, but functional state.
> Happy to create a PR, however I don't have a lot of free time at home at the
> moment, so it may take a week or two.
>
> Additional info:
> See below for example mntr output for the Leader/Follower/Observer roles,
> noting the Leader's zk_followers and zk_synced_followers values, and the
> values of zk_server_state.
> Leader:
> {code:java}
> [root@master1 ~]# echo mntr | nc master3 12181
> zk_version 3.5.6-c11b7e26bc554b8523dc929761dd28808913f091, built on
> 10/08/2019 20:18 GMT
> zk_avg_latency 0
> zk_max_latency 2
> zk_min_latency 0
> zk_packets_received 97
> zk_packets_sent 96
> zk_num_alive_connections 2
> zk_outstanding_requests 0
> zk_server_state leader
> zk_znode_count 92
> zk_watch_count 7
> zk_ephemerals_count 9
> zk_approximate_data_size 236333
> zk_open_file_descriptor_count 64
> zk_max_file_descriptor_count 4096
> zk_followers 4
> zk_synced_followers 2
> zk_pending_syncs 0
> zk_last_proposal_size -1
> zk_max_proposal_size -1
> zk_min_proposal_size -1
> {code}
> Follower:
> {code:java}
> [root@master1 ~]# echo mntr | nc master2 12181
> zk_version 3.5.6-c11b7e26bc554b8523dc929761dd28808913f091, built on
> 10/08/2019 20:18 GMT
> zk_avg_latency 0
> zk_max_latency 6
> zk_min_latency 0
> zk_packets_received 97
> zk_packets_sent 96
> zk_num_alive_connections 2
> zk_outstanding_requests 0
> zk_server_state follower
> zk_znode_count 92
> zk_watch_count 7
> zk_ephemerals_count 9
> zk_approximate_data_size 236333
> zk_open_file_descriptor_count 60
> zk_max_file_descriptor_count 4096
> {code}
> Observer:
> {code:java}
> [root@master1 ~]# echo mntr | nc slave1 12181
> zk_version 3.5.6-c11b7e26bc554b8523dc929761dd28808913f091, built on
> 10/08/2019 20:18 GMT
> zk_avg_latency 0
> zk_max_latency 8
> zk_min_latency 0
> zk_packets_received 174
> zk_packets_sent 173
> zk_num_alive_connections 2
> zk_outstanding_requests 0
> zk_server_state observer
> zk_znode_count 92
> zk_watch_count 7
> zk_ephemerals_count 9
> zk_approximate_data_size 236333
> zk_open_file_descriptor_count 59
> zk_max_file_descriptor_count 4096
> {code}
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