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https://reviews.apache.org/r/17678/
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Review request for hive.
Bugs: HIVE-4996
https://issues.apache.org/jira/browse/HIVE-4996
Repository: hive-git
Description
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Background:
First issue:
There are two levels of retrying in case of transient JDO/CP/DB errors: the
RetryingHMSHandler and RetryingMetaStore. But the RetryingMetaStore is flawed
in the case of a nested transaction of a larger RetryingHMSHandler transaction
(which is majority of cases).
Consider the following sample RetryingHMSHandler call, where variable "ms" is a
RetryingRawStore.
HMSHandler.createTable()
ms.open() //openTx = 1
ms.getTable() // openTx = 2, then openTx = 1 upon intermediate commit
ms.createTable() //openTx = 2, then openTx = 1 upon intermediate commit
ms.commit(); //openTx = 0
If there is any transient error in any intermediate operation and
RetryingRawStore tries again, there will always be an unbalanced transaction,
like:
HMSHandler.createTable()
ms.open() //openTx = 1
ms.getTable() // openTx = 2, transient error, then openTx=0 upon
rollback. After a retry, openTx=1, then openTx=0 upon successful intermediate
commit
ms.createTable() //openTx = 1, then openTx = 0 upon intermediate commit
ms.commit(); //unbalanced transaction!
Retrying RawStore operations doesn't make sense in nested transaction cases, as
the first part of the transaction is rolled-back upon transient error, and
retry logic only saves a second half which may not make sense without the
first. It makes much more sense to retry the entire transaction from the top,
which is what RetryingHMSHandler would already be doing if the
RetryingMetaStore did not interfere.
Second issue:
The recent upgrade to BoneCP 0.8.0 seemed to cause more transient errors that
triggered this problem. In these cases, in-use connections are finalized, as
follows:
WARN bonecp.ConnectionPartition
(ConnectionPartition.java:finalizeReferent(162)) - BoneCP detected an unclosed
connection and will now attempt to close it for you. You should be closing this
connection in your application - enable connectionWatch for additional
debugging assistance or set disableConnectionTracking to true to disable this
feature entirely.
The retry of this operation seems to get a good connection and allow the
operation to proceed. Reading forums, it seems some others have hit this issue
after the upgrade, and switching back to 0.7.1 in our environment eliminated
this issue for us. But that reversion is outside the scope of this JIRA, and
would be better-done in either the original or follow-up JIRA that upgraded the
version.
This fix targets the first issue only, as anyway it is needed for any sort of
transient error, not just the BoneCP one that I observed.
Changes:
1. Removes RetryingRawStore in favor of RetryingHMSHandler, and removes the
configuration property of the former.
2. Addresses the resultant holes in retry, in particular in the
RetryingHMSHandler's construction of RawStore (before, RetryingRawStore would
have retried failures like in creating the defaultDB). It didn't seem
necessary to increase the default RetryingHMSHandler retries to 2 to
compensate, but I am open to that as well.
3. Contribute the instrumentation code that helped me to find the issue. This
includes printing missing stacks of exceptions that triggered retry, and adding
debug-level tracing of ObjectStore calls to give better correlation with other
errors/warnings in hive log.
Diffs
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common/src/java/org/apache/hadoop/hive/conf/HiveConf.java 22bb22d
itests/hive-unit/src/test/java/org/apache/hadoop/hive/metastore/TestHiveMetaStore.java
d7854fe
itests/hive-unit/src/test/java/org/apache/hadoop/hive/metastore/TestRawStoreTxn.java
0b87077
metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java
2d8e483
metastore/src/java/org/apache/hadoop/hive/metastore/ObjectStore.java 0715e22
metastore/src/java/org/apache/hadoop/hive/metastore/RetryingHMSHandler.java
fb70589
metastore/src/java/org/apache/hadoop/hive/metastore/RetryingRawStore.java
dcf97ec
Diff: https://reviews.apache.org/r/17678/diff/
Testing
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Thanks,
Szehon Ho
