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https://issues.apache.org/jira/browse/HDFS-11296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15803903#comment-15803903
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Lei (Eddy) Xu commented on HDFS-11296:
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Hi, [~manojg]
Thanks for working on this. I have a few questions regarding to this patch.
There were a few efforts to replace wall time with {{monotonicNow()}} in the
past, for example, HDFS-6841 and HDFS-6453. In general, different nodes can
not guarantee time are synchronized, i.e., between clients, NameNode and
DataNodes.
Btw, IIUC, the expiration time set by client is the delta time instead of
absolute time?
> Maintenance state expiry should be an epoch time and not jvm monotonic
> ----------------------------------------------------------------------
>
> Key: HDFS-11296
> URL: https://issues.apache.org/jira/browse/HDFS-11296
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: 3.0.0-alpha1
> Reporter: Manoj Govindassamy
> Assignee: Manoj Govindassamy
> Attachments: HDFS-11296.01.patch
>
>
> Currently it is possible to configure an expiry time in milliseconds for a
> DataNode in maintenance state. As per the design, the expiry attribute is an
> absolute time, beyond which NameNode starts to stop the ongoing maintenance
> operation for that DataNode. Internally in the code, this expiry time is read
> and checked against {{Time.monotonicNow()}} making the expiry based on more
> of JVM's runtime, which is very difficult to configure for any external user.
> The goal is to make the expiry time an absolute epoch time, so that its easy
> to configure for external users.
> {noformat}
> {
> "hostName": <host>,
> "port": <port>,
> "adminState": "IN_MAINTENANCE",
> "maintenanceExpireTimeInMS": <time in millis>
> }
> {noformat}
> DatanodeInfo.java
> {noformat}
> public static boolean maintenanceNotExpired(long maintenanceExpireTimeInMS)
> {
> return Time.monotonicNow() < maintenanceExpireTimeInMS;
> }
> {noformat}
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