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https://issues.apache.org/jira/browse/HBASE-21582?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16717171#comment-16717171
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Zheng Hu commented on HBASE-21582:
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Read the code, we cannot just remove the handler from ConcurentHashMap,
because the isSnapshotDone will throw the handler's exception to user, If we
just remove the handler from Map after it be finshied, then the exception will
lost too. So I introduced a period thread to cleanup the finished handler.
> If call HBaseAdmin#snapshotAsync but forget call isSnapshotFinished, then
> SnapshotHFileCleaner will skip to run every time
> --------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-21582
> URL: https://issues.apache.org/jira/browse/HBASE-21582
> Project: HBase
> Issue Type: Bug
> Reporter: Zheng Hu
> Assignee: Zheng Hu
> Priority: Major
> Attachments: HBASE-21582.v1.patch
>
>
> This is because we remove the SnapshotSentinel from snapshotHandlers in
> SnapshotManager#cleanupSentinels. Only when the following 3 case, the
> cleanupSentinels will be called:
> 1. SnapshotManager#isSnapshotDone;
> 2. SnapshotManager#takeSnapshot;
> 3. SnapshotManager#restoreOrCloneSnapshot
> So if no isSnapshotDone called, or no further snapshot taking, or snapshot
> restore/clone. the SnapshotSentinel will always be keep in snapshotHandlers.
> But after HBASE-21387, Only when no snapshot taking, the
> SnapshotHFileCleaner will check the unref files and clean.
> I found this bug, because in our XiaoMi branch-2, we implement the soft
> delete feature, which means if someone delete a table, then master will
> create a snapshot firstly, after that, the table deletion begain. the
> implementation is quite simple, we use the snapshotManager to create a
> snapshot.
> {code}
> diff --git
> a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java
> b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java
> index 8f42e4a..6da6a64 100644
> --- a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java
> +++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java
> @@ -2385,12 +2385,6 @@ public class HMaster extends HRegionServer implements
> MasterServices {
> protected void run() throws IOException {
> getMaster().getMasterCoprocessorHost().preDeleteTable(tableName);
>
> + if (snapshotBeforeDelete) {
> + LOG.info("Take snaposhot for " + tableName + " before deleting");
> + snapshotManager
> +
> .takeSnapshot(SnapshotDescriptionUtils.getSnapshotNameForDeletedTable(tableName));
> + }
> +
> LOG.info(getClientIdAuditPrefix() + " delete " + tableName);
>
> // TODO: We can handle/merge duplicate request
> {code}
> In the master, I found the endless log after delete a table:
> {code}
> org.apache.hadoop.hbase.master.snapshot.SnapshotFileCache: Not checking
> unreferenced files since snapshot is running, it will skip to clean the
> HFiles this time
> {code}
> This is because the snapshotHandlers never be cleaned after call the
> snapshotManager#takeSnapshot. I think the asynSnapshot may has the same
> problem.
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