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https://issues.apache.org/jira/browse/ZOOKEEPER-2627?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Han updated ZOOKEEPER-2627:
-----------------------------------
Attachment: ZOOKEEPER-2627.patch
> Remove ZRWSERVERFOUND from C client and replace handle_error with something
> more semantically explicit for r/w server reconnect.
> --------------------------------------------------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-2627
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2627
> Project: ZooKeeper
> Issue Type: Bug
> Components: c client
> Affects Versions: 3.5.2
> Reporter: Michael Han
> Assignee: Michael Han
> Fix For: 3.5.3
>
> Attachments: ZOOKEEPER-2627.patch
>
>
> While working on ZOOKEEPER-2014, I noticed a discrepancy between Java and C
> client regarding the error codes definition. There is a
> {noformat}ZRWSERVERFOUND = -122{noformat} definition in C client which is not
> present in Java client's KeeperException.Code definitions.
> This discrepancy was introduced by ZOOKEEPER-827, where the C client logic
> was simulating the Java client's logic when doing a read/write server search
> while client is in read only mode. Once client finds a valid read/write
> server, client will try to disconnect and reconnect with this read/write
> server, as we always prefer r/w server in ro mode. The way Java client is
> doing this disconnect/reconnect process is by throwing a
> RWServerFoundException (instead of a KeeperException) to set the client in
> disconnected state, then wait for client reconnect with r/w server address
> set before throwing the exception. C client did similar but instead of having
> an explicitly disconnect / clean up routine, the client was relying on
> handle_error to do the job where ZRWSERVERFOUND was introduced.
> I propose we remove ZRWSERVERFOUND error code from C client and use an
> explicit routine instead of handle_error when we do r/w server search in C
> client for two reasons:
> * ZRWSERVERFOUND is not something ZK client users would need to know. It's a
> pure implementation detail that's used to alter the connection state of the
> client, and ZK client users have no desire nor need to handle such errors, as
> R/W server scanning and connect is handled transparently by ZK client library.
> * To maintain consistency between Java and C client regarding error codes
> definition. Without removing this from C client, we would need to replace
> RWServerFoundException in Java client with a new KeeperException, and again
> with the reason mentioned above, we don't need a KeeperException for this
> because such implementation detail does not have to be exposed to end users
> (unless, we provided alternative for users to opt-out automate R/W server
> switching when in read only mode which we don't.).
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