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https://issues.apache.org/jira/browse/HIVE-19261?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Fangshi Li updated HIVE-19261:
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Description:
In HIVE-16175, upstream made a patch to fix the thread safety issue in
AvroSerDe's InstanceCache. This fix made the retrieve method in InstanceCache
synchronized. While it should make InstanceCache thread-safe, making retrieve
synchronized for the cache can be expensive in highly concurrent environment
like Spark, as multiple threads need to be synchronized on entering the entire
retrieve method.
We are proposing another way to fix this thread safety issue by making the
underlying map of InstanceCache as ConcurrentHashMap. Ideally, we can use
atomic computeIfAbsent in the retrieve method to avoid synchronizing the entire
method.
While computeIfAbsent is only available on java 8 and java 7 is still supported
in Hive,
we use a pattern to simulate the behavior of computeIfAbsent. In the future, we
should move to computeIfAbsent when Hive requires java 8.
was:
In HIVE-16175, upstream made a patch to fix the thread safety issue in
AvroSerDe's InstanceCache. This fix made the retrieve method in InstanceCache
synchronized. While it should make InstanceCache thread-safe, making retrieve
synchronized for the cache can be expensive in highly concurrent environment
like Spark, as multiple threads need to be synchronized on entering the entire
retrieve method.
We are proposing another way to fix this thread safety issue by making the
underlying map of InstanceCache as ConcurrentHashMap. Ideally, we can use
atomic computeIfAbsent in the retrieve method to avoid synchronizing the entire
method.
While computeIfAbsent is only available on java 8 and java 7 is still supported
in Hive,
/we use a pattern to simulate the behavior of computeIfAbsent. In the future,
we should move to computeIfAbsent when Hive requires java 8.
> Avro SerDe's InstanceCache should not be synchronized on retrieve
> -----------------------------------------------------------------
>
> Key: HIVE-19261
> URL: https://issues.apache.org/jira/browse/HIVE-19261
> Project: Hive
> Issue Type: Improvement
> Reporter: Fangshi Li
> Assignee: Fangshi Li
> Priority: Major
>
> In HIVE-16175, upstream made a patch to fix the thread safety issue in
> AvroSerDe's InstanceCache. This fix made the retrieve method in InstanceCache
> synchronized. While it should make InstanceCache thread-safe, making retrieve
> synchronized for the cache can be expensive in highly concurrent environment
> like Spark, as multiple threads need to be synchronized on entering the
> entire retrieve method.
> We are proposing another way to fix this thread safety issue by making the
> underlying map of InstanceCache as ConcurrentHashMap. Ideally, we can use
> atomic computeIfAbsent in the retrieve method to avoid synchronizing the
> entire method.
> While computeIfAbsent is only available on java 8 and java 7 is still
> supported in Hive,
> we use a pattern to simulate the behavior of computeIfAbsent. In the future,
> we should move to computeIfAbsent when Hive requires java 8.
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