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https://issues.apache.org/jira/browse/HDFS-17055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17736312#comment-17736312
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ASF GitHub Bot commented on HDFS-17055:
---------------------------------------
xinglin commented on code in PR #5764:
URL: https://github.com/apache/hadoop/pull/5764#discussion_r1239137137
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hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java:
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@@ -2051,6 +2056,26 @@ synchronized HAServiceState getServiceState() {
return state.getServiceState();
}
+ /**
+ * Emit Namenode HA service state as an integer so that one can monitor NN HA
+ * state based on this metric.
+ *
+ * @return 0 when not fully started
+ * 1 for active or standalone (non-HA) NN
+ * 2 for standby
+ * 3 for observer
+ *
Review Comment:
Searching codebase, it seems we would set a state to STOPPING state only in
YARN ResourceManager HA. We are not using that state in HDFS.
> Export HAState as a metric from Namenode for monitoring
> -------------------------------------------------------
>
> Key: HDFS-17055
> URL: https://issues.apache.org/jira/browse/HDFS-17055
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs
> Affects Versions: 3.4.0, 3.3.9
> Reporter: Xing Lin
> Assignee: Xing Lin
> Priority: Minor
> Labels: pull-request-available
>
> We'd like measure the uptime for Namenodes: percentage of time when we have
> the active/standby/observer node available (up and running). We could monitor
> the namenode from an external service, such as ZKFC. But that would require
> the external service to be available 100% itself. And when this third-party
> external monitoring service is down, we won't have info on whether our
> Namenodes are still up.
> We propose to take a different approach: we will emit Namenode state directly
> from namenode itself. Whenever we miss a data point for this metric, we
> consider the corresponding namenode to be down/not available. In other words,
> we assume the metric collection/monitoring infrastructure to be 100% reliable.
> One implementation detail: in hadoop, we have the _NameNodeMetrics_ class,
> which is currently used to emit all metrics for {_}NameNode.java{_}. However,
> we don't think that is a good place to emit NameNode HAState. HAState is
> stored in NameNode.java and we should directly emit it from NameNode.java.
> Otherwise, we basically duplicate this info in two classes and we would have
> to keep them in sync. Besides, _NameNodeMetrics_ class does not have a
> reference to the _NameNode_ object which it belongs to. An _NameNodeMetrics_
> is created by a _static_ function _initMetrics()_ in {_}NameNode.java{_}.
> We shouldn't emit HA state from FSNameSystem.java either, as it is
> initialized from NameNode.java and all state transitions are implemented in
> NameNode.java.
>
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