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https://issues.apache.org/jira/browse/HDFS-17955?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18101023#comment-18101023
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ASF GitHub Bot commented on HDFS-17955:
---------------------------------------
pan3793 opened a new pull request, #8649:
URL: https://github.com/apache/hadoop/pull/8649
### Description of PR
The Checkpointer triggers the first checkpoint when
`shouldCheckpointAtStartup()` returns true by leaving `lastCheckpointTime =
0`
and relying on `now >= lastCheckpointTime + checkpointPeriodMSec` to
evaluate true. This condition breaks when `monotonicNow()`
(`System.nanoTime` based) returns a value smaller than
`checkpointPeriodMSec` (3600000ms = 1 hour), which happens on freshly
booted VMs such as GitHub-hosted runners. The checkpoint never fires,
and any caller waiting for it hangs indefinitely.
Add an explicit `lastCheckpointTime == 0` check so the first checkpoint
fires immediately regardless of the monotonic clock value. After the
first checkpoint, `lastCheckpointTime` is set to the current time and
normal period-based scheduling resumes.
This is a latent bug present since the Checkpointer logic was introduced
in 2011 (a196766). It was exposed by the GitHub-hosted runner image
`ubuntu24/20260720.247`, which provisions VMs fast enough that host
uptime is below 1 hour at test execution. A BackupNode that restarts
within 1 hour of boot on any deployment has the same bug.
### How was this patch tested?
Verified via GitHub Actions CI on a fork branch. Before the fix,
`TestBackupNode` hangs indefinitely (fork timeout after 900s). After the
fix, the Checkpointer fires the startup checkpoint immediately and
`TestBackupNode` passes.
### For code changes:
- [x] Does the title or this PR starts with the corresponding JIRA issue id
(HDFS-17955)?
- [ ] Object storage: have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
### AI Tooling
If an AI tool was used:
- [x] The PR includes the phrase "Contains content generated by GLM 5.2"
where GLM 5.2 is the name of the AI tool used.
- [x] My use of AI contributions follows the ASF legal policy
https://www.apache.org/legal/generative-tooling.html
Contains content generated by GLM 5.2
> Fix Checkpointer startup checkpoint on fresh VMs
> ------------------------------------------------
>
> Key: HDFS-17955
> URL: https://issues.apache.org/jira/browse/HDFS-17955
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Reporter: Cheng Pan
> Priority: Major
>
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