Na Li created SENTRY-2299:
-----------------------------
Summary: NPE In Sentry HDFS Sync Plug
Key: SENTRY-2299
URL: https://issues.apache.org/jira/browse/SENTRY-2299
Project: Sentry
Issue Type: Bug
Components: Sentry
Affects Versions: 2.1.0
Reporter: Na Li
Sentry HDFS ACL synchronization stopped working and throws
NullPointerException. The HDFS logs showed repeating errors like the following:
{code}
11:16:15.743 AM WARN SentryAuthorizationInfo
Failed to update, will retry in [30000]ms, error:
java.lang.NullPointerException
at org.apache.sentry.hdfs.HMSPaths$Entry.access$200(HMSPaths.java:146)
at org.apache.sentry.hdfs.HMSPaths.renameAuthzObject(HMSPaths.java:879)
at
org.apache.sentry.hdfs.UpdateableAuthzPaths.applyPartialUpdate(UpdateableAuthzPaths.java:118)
at
org.apache.sentry.hdfs.UpdateableAuthzPaths.updatePartial(UpdateableAuthzPaths.java:81)
at
org.apache.sentry.hdfs.SentryAuthorizationInfo.processUpdates(SentryAuthorizationInfo.java:211)
at
org.apache.sentry.hdfs.SentryAuthorizationInfo.update(SentryAuthorizationInfo.java:139)
at
org.apache.sentry.hdfs.SentryAuthorizationInfo.run(SentryAuthorizationInfo.java:232)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
The customer checked the Sentry logs and didn't see any corresponding errors.
The issue stopped occurring, apparently not through any specific user
intervention. (The customer tried manually failing over the active NameNode,
with no change.)
{code}
Arjun mentioned the reason is that some delta update from sentry server was
lost, so the oldEntry at line HMSPaths.java:879 was null. That caused null
exception.
{code}
void renameAuthzObject(String oldName, List<List<String>> oldPathElems,
String newName, List<List<String>> newPathElems) {
if (LOG.isDebugEnabled()) {
LOG.debug(String.format("%s renameAuthzObject({%s, %s} -> {%s, %s})",
this, oldName, assemblePaths(oldPathElems), newName,
assemblePaths(newPathElems)));
}
if (oldPathElems == null || oldPathElems.isEmpty() ||
newPathElems == null || newPathElems.isEmpty() ||
newName == null || newName.equals(oldName)) {
LOG.warn(String.format("%s renameAuthzObject({%s, %s} -> {%s, %s})" +
": invalid inputs, skipping",
this, oldName, assemblePaths(oldPathElems), newName,
assemblePaths(newPathElems)));
return;
}
// if oldPath == newPath, that is path has not changed as part of rename
and hence new table
// needs to have old paths => new_table.add(old_table_partition_paths)
List<String> oldPathElements = oldPathElems.get(0);
List<String> newPathElements = newPathElems.get(0);
if (!oldPathElements.equals(newPathElements)) {
Entry oldEntry = root.find(oldPathElements.toArray(new String[0]), false);
Entry newParent = root.createParent(newPathElements);
oldEntry.moveTo(newParent, newPathElements.get(newPathElements.size() -
1)); -> oldEntry is null
}
{code}
There are several possible reasons why some delta changes are lost.
{code}
1. Sentry server does not save the rename update as delta update. The chance is
really low
2. The delta change is lost from sentry server to name node plugin. The chance
is also low
3. When applying delta change about old entry, it is lost
{code}
The fix for this issue
1. Check if oldEntry is null. If so, don't call oldEntry.moveTo. Instead, throw
exception, which will be caught by its caller and causes sentry client at name
node plugin gets path full snapshot from sentry server.
2. Find out why the oldEntry is null and fix it.
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