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https://issues.apache.org/jira/browse/HDFS-13220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16914215#comment-16914215
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Surendra Singh Lilhore commented on HDFS-13220:
-----------------------------------------------
If we see the code, {{monotonicNow()}} used because they want to avoid check
pointing on startup.
{code:java}
// Reset checkpoint time so that we don't always checkpoint
// on startup.
lastCheckpointTime = monotonicNow(); {code}
This is fine when default checkpoint interval (3600s) is used, but if user
changed this configuration and increase this time then it will delay the check
pointing. Better always trigger first check pointing after default interval and
next time based on user configuration.
> Change lastCheckpointTime to use fsimage mostRecentCheckpointTime
> -----------------------------------------------------------------
>
> Key: HDFS-13220
> URL: https://issues.apache.org/jira/browse/HDFS-13220
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Reporter: Nie Gus
> Priority: Minor
>
> we found the our standby nn did not do the checkpoint, and the checkpoint
> alert keep alert, we use the jmx last checkpoint time and
> dfs.namenode.checkpoint.period to do the monitor check.
>
> then check the code and log, found the standby NN are using monotonicNow, not
> fsimage checkpoint time, so when Standby NN restart or switch to Active, then
> the
> lastCheckpointTime in doWork will be reset. so there is risk standby nn
> restart or stand active switch will cause the checkpoint delay.
> StandbyCheckpointer.java
> {code:java}
> private void doWork() {
> final long checkPeriod = 1000 * checkpointConf.getCheckPeriod();
> // Reset checkpoint time so that we don't always checkpoint
> // on startup.
> lastCheckpointTime = monotonicNow();
> while (shouldRun) {
> boolean needRollbackCheckpoint = namesystem.isNeedRollbackFsImage();
> if (!needRollbackCheckpoint) {
> try {
> Thread.sleep(checkPeriod);
> } catch (InterruptedException ie) {
> }
> if (!shouldRun) {
> break;
> }
> }
> try {
> // We may have lost our ticket since last checkpoint, log in again, just in
> case
> if (UserGroupInformation.isSecurityEnabled()) {
> UserGroupInformation.getCurrentUser().checkTGTAndReloginFromKeytab();
> }
> final long now = monotonicNow();
> final long uncheckpointed = countUncheckpointedTxns();
> final long secsSinceLast = (now - lastCheckpointTime) / 1000;
> boolean needCheckpoint = needRollbackCheckpoint;
> if (needCheckpoint) {
> LOG.info("Triggering a rollback fsimage for rolling upgrade.");
> } else if (uncheckpointed >= checkpointConf.getTxnCount()) {
> LOG.info("Triggering checkpoint because there have been " +
> uncheckpointed + " txns since the last checkpoint, which " +
> "exceeds the configured threshold " +
> checkpointConf.getTxnCount());
> needCheckpoint = true;
> } else if (secsSinceLast >= checkpointConf.getPeriod()) {
> LOG.info("Triggering checkpoint because it has been " +
> secsSinceLast + " seconds since the last checkpoint, which " +
> "exceeds the configured interval " + checkpointConf.getPeriod());
> needCheckpoint = true;
> }
> synchronized (cancelLock) {
> if (now < preventCheckpointsUntil) {
> LOG.info("But skipping this checkpoint since we are about to failover!");
> canceledCount++;
> continue;
> }
> assert canceler == null;
> canceler = new Canceler();
> }
> if (needCheckpoint) {
> doCheckpoint();
> // reset needRollbackCheckpoint to false only when we finish a ckpt
> // for rollback image
> if (needRollbackCheckpoint
> && namesystem.getFSImage().hasRollbackFSImage()) {
> namesystem.setCreatedRollbackImages(true);
> namesystem.setNeedRollbackFsImage(false);
> }
> lastCheckpointTime = now;
> }
> } catch (SaveNamespaceCancelledException ce) {
> LOG.info("Checkpoint was cancelled: " + ce.getMessage());
> canceledCount++;
> } catch (InterruptedException ie) {
> LOG.info("Interrupted during checkpointing", ie);
> // Probably requested shutdown.
> continue;
> } catch (Throwable t) {
> LOG.error("Exception in doCheckpoint", t);
> } finally {
> synchronized (cancelLock) {
> canceler = null;
> }
> }
> }
> }
> }
> {code}
>
> can we use the fsimage's mostRecentCheckpointTime to do the check.
>
> thanks,
> Gus
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