Nathan Roberts created HDFS-7645:
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Summary: Rolling upgrade is restoring blocks from trash multiple
times
Key: HDFS-7645
URL: https://issues.apache.org/jira/browse/HDFS-7645
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode
Affects Versions: 2.6.0
Reporter: Nathan Roberts
When performing an HDFS rolling upgrade, the trash directory is getting
restored twice when under normal circumstances it shouldn't need to be restored
at all. iiuc, the only time these blocks should be restored is if we need to
rollback a rolling upgrade.
On a busy cluster, this can cause significant and unnecessary block churn both
on the datanodes, and more importantly in the namenode.
The two times this happens are:
1) restart of DN onto new software
{code}
private void doTransition(DataNode datanode, StorageDirectory sd,
NamespaceInfo nsInfo, StartupOption startOpt) throws IOException {
if (startOpt == StartupOption.ROLLBACK && sd.getPreviousDir().exists()) {
Preconditions.checkState(!getTrashRootDir(sd).exists(),
sd.getPreviousDir() + " and " + getTrashRootDir(sd) + " should not " +
" both be present.");
doRollback(sd, nsInfo); // rollback if applicable
} else {
// Restore all the files in the trash. The restored files are retained
// during rolling upgrade rollback. They are deleted during rolling
// upgrade downgrade.
int restored = restoreBlockFilesFromTrash(getTrashRootDir(sd));
LOG.info("Restored " + restored + " block files from trash.");
}
{code}
2) When heartbeat response no longer indicates a rollingupgrade is in progress
{code}
/**
* Signal the current rolling upgrade status as indicated by the NN.
* @param inProgress true if a rolling upgrade is in progress
*/
void signalRollingUpgrade(boolean inProgress) throws IOException {
String bpid = getBlockPoolId();
if (inProgress) {
dn.getFSDataset().enableTrash(bpid);
dn.getFSDataset().setRollingUpgradeMarker(bpid);
} else {
dn.getFSDataset().restoreTrash(bpid);
dn.getFSDataset().clearRollingUpgradeMarker(bpid);
}
}
{code}
HDFS-6800 and HDFS-6981 were modifying this behavior making it not completely
clear whether this is somehow intentional.
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