[jira] [Commented] (HBASE-15992) Preserve original KeeperException when converted to external exceptions

["Andrew Purtell (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-15992?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15321282#comment-15321282 ] 

Andrew Purtell commented on HBASE-15992:
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Thanks for filing this [~haridsv]. I agree we should preserve information on the original cause and be smarter about what type of exception to rethrow where the failure indicates a more permanent condition. Do you plan on working on a patch or would you like to hand it off for someone else to look at?

> 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
>              Labels: client, client-auth, zookeeper
>
> 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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