Hari Krishna Dara created HBASE-15992:
-----------------------------------------
Summary: Preserve original KeeperException when converted to
external exceptions
Key: HBASE-15992
URL: https://issues.apache.org/jira/browse/HBASE-15992
Project: HBase
Issue Type: Brainstorming
Components: hbase
Affects Versions: 0.98.14
Reporter: Hari Krishna Dara
Priority: Minor
During an investigation in which we were seeing unexpected
{{NoServerForRegionException}} errors, the root cause turned out to be a
{{KeeperException}} that got lost and so resulted in a misleading top level
indication.
The underlying exception with partial stacktrace is this:
{noformat}
org.apache.zookeeper.KeeperException$AuthFailedException: KeeperErrorCode =
AuthFailed for /hbase/meta-region-server
at org.apache.zookeeper.KeeperException.create(KeeperException.java:123)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1289)
at
org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.getData(RecoverableZooKeeper.java:359)
at org.apache.hadoop.hbase.zookeeper.ZKUtil.getData(ZKUtil.java:684)
at
org.apache.hadoop.hbase.zookeeper.ZKUtil.blockUntilAvailable(ZKUtil.java:2032)
at
org.apache.hadoop.hbase.zookeeper.MetaRegionTracker.blockUntilAvailable(MetaRegionTracker.java:203)
at
org.apache.hadoop.hbase.client.ZooKeeperRegistry.getMetaRegionLocation(ZooKeeperRegistry.java:58)
at
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateMeta(HConnectionManager.java:1209)
at
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1175)
at
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:1301)
at
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1178)
at
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1135)
at
org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionLocation(HConnectionManager.java:976)
{noformat}
Here is some additional information:
* The exception first gets caught
[here|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java#L366]
* It gets logged and rethrown from
[here|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java#L279]
* It gets caught again, logged and rethrown
[here|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKUtil.java#L693]
* This finally gets caught and rethrown as InterruptedException
[here|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKUtil.java#L2037]
When thrown as {{InterruptedException}}, the cause is lost, so [the code
catching
it|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/client/ZooKeeperRegistry.java#L65]
can't (and currently doesn't) determine the cause. Perhaps the exception
should be preserved and passed on to [the
caller|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java#L1312]
such that it is available when finally the {{NoServerForRegionException}} is
thrown
[here|https://github.com/apache/hbase/blob/rel/0.98.14/hbase-client/src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java#L1281].
Alternatively, a more meaningful exception could also be thrown instead of a
misleading {{NoServerForRegionException}}, especially in cases where the
failure indicates a more permanent condition.
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