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https://issues.apache.org/jira/browse/HBASE-3787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13567864#comment-13567864
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Andrew Purtell edited comment on HBASE-3787 at 1/31/13 5:52 PM:
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I think the above comments all taken together are a reasonable thing to try:
- Introduce a nonce (generated internally by the client) on non-idempotent
operations to convert them into idempotent ones.
- nonce = hash(client address, table, row, timestamp)
- HBaseClient should generate a new nonce whenever a new op is sent to new
server. Reuse the nonce for any retry.
- Server tracks nonces by (client address, nonce, timestamp). Expire entries
after some grace period. Restart the expiration timer whenever the nonce is
checked as part of op processing. Lazily clean up expired entries either as
part of add/remove or via a chore.
- Add the entry when op processing starts, remove it when finished or failed,
refuse to process an op twice by sending back a DoNotRetryException. Perhaps we
introduce a new exception type like OperationInProgressException which inherits
from DoNotRetryException so the client understands the retry operation was
failed because the previous attempt is still pending server side.
- We should append the nonce to the WALEdit, and recover them along with the
entry data.
was (Author: apurtell):
I think the above comments all taken together are a reasonable thing to try:
- Introduce a nonce (generated internally by the client) on non-idempotent
operations to convert them into idempotent ones.
- nonce = hash(client address, table, row, timestamp)
- HBaseClient should generate a new nonce whenever a new op is sent to new
server. Reuse the nonce for any retry.
- Server tracks nonces by (client address, nonce, timestamp)
- Add the entry when op processing starts, remove it when finished or failed,
refuse to process an op twice by sending back a DoNotRetryException. Perhaps we
introduce a new exception type like OperationInProgressException which inherits
from DoNotRetryException so the client understands the retry operation was
failed because the previous attempt is still pending server side.
- We should append the nonce to the WALEdit, and recover them along with the
entry data.
> Increment is non-idempotent but client retries RPC
> --------------------------------------------------
>
> Key: HBASE-3787
> URL: https://issues.apache.org/jira/browse/HBASE-3787
> Project: HBase
> Issue Type: Bug
> Components: Client
> Affects Versions: 0.96.0, 0.94.4
> Reporter: dhruba borthakur
> Priority: Critical
> Fix For: 0.96.0
>
>
> The HTable.increment() operation is non-idempotent. The client retries the
> increment RPC a few times (as specified by configuration) before throwing an
> error to the application. This makes it possible that the same increment call
> be applied twice at the server.
> For increment operations, is it better to use
> HConnectionManager.getRegionServerWithoutRetries()? Another option would be
> to enhance the IPC module to make the RPC server correctly identify if the
> RPC is a retry attempt and handle accordingly.
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