Yi Liu created HDFS-6786:
----------------------------
Summary: Fix potential issue of cache refresh interval
Key: HDFS-6786
URL: https://issues.apache.org/jira/browse/HDFS-6786
Project: Hadoop HDFS
Issue Type: Bug
Components: caching
Affects Versions: 3.0.0
Reporter: Yi Liu
Assignee: Yi Liu
In {{CacheReplicationMonitor}}, following code is try to check whether needs to
rescan every interval ms, if rescan takes n ms, then subtract n ms for the
interval. But if the delta <=0, it breaks and start rescan, there will be
potential issue: if user set the interval to a small value or rescan finished
after a while exceeding the interval, then rescan will happen in loop.
Furthermore, {{delta <= 0}} trigger the rescan should not be the intention,
since if needs rescan, {{needsRescan}} will be set.
{code}
while (true) {
if (shutdown) {
LOG.info("Shutting down CacheReplicationMonitor");
return;
}
if (needsRescan) {
LOG.info("Rescanning because of pending operations");
break;
}
long delta = (startTimeMs + intervalMs) - curTimeMs;
if (delta <= 0) {
LOG.info("Rescanning after " + (curTimeMs - startTimeMs) +
" milliseconds");
break;
}
doRescan.await(delta, TimeUnit.MILLISECONDS);
curTimeMs = Time.monotonicNow();
}
{code}
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