Tephra + Phoenix - configuration for high availability

[Curtis Howard <cu...@gmail.com>]

Hi,

We are using Tephra to support transactions with Phoenix and would like to
configure Tephra in HA mode.
It seems that one option could be through the CFG_DATA_TX_ZOOKEEPER_QUORUM
property:
https://github.com/apache/incubator-tephra/blob/d0a1c4c295fd28e68223db220b13dc1b12b326da/tephra-core/src/main/java/org/apache/tephra/TxConstants.java#L224-L226

I've tested this with a couple of Tephra manager processes on different
hosts, and they do seem to pass off control as the leader/standby
instance.   It's not clear to me though how "in-flight" transactions that
have been initiated but not committed yet would be handled during a
failover?

Is this the recommended approach?  Are the any other settings besides
CFG_DATA_TX_ZOOKEEPER_QUORUM that we need to consider?

Thank you!
Curtis

Re: Tephra + Phoenix - configuration for high availability

[Curtis Howard <cu...@gmail.com>]

Hi Andreas,

Thanks very much for the quick response!  We will go ahead with this HA
approach using CFG_DATA_TX_ZOOKEEPER_QUORUM.

Curtis

On Fri, Nov 9, 2018 at 1:08 PM Andreas Neumann <an...@apache.org> wrote:

> Hi Curtis,
>
> All changes to the transaction state, including in-process transactions,
> are captured in the transaction log. When a failover occurs, the new
> transaction manager recreates the entire transaction state by replaying the
> log from the last snapshot. In-flight transactions should still be able to
> commit normally. It could happen, however, that a client rolls back during
> the short time that the transaction manager is down. That client would not
> be able to notify the tx manager that it has rolled back its transaction.
> Such a transaction would time out and become an invalid transaction.
>
> This is tested (not for failover, but for restart) here:
>
> https://github.com/apache/incubator-tephra/blob/master/tephra-core/src/test/java/org/apache/tephra/persist/AbstractTransactionStateStorageTest.java#L124
>
> Cheers -Andreas
>
> On Fri, Nov 9, 2018 at 6:17 AM Curtis Howard <
> curtis.james.howard@gmail.com>
> wrote:
>
> > Hi,
> >
> > We are using Tephra to support transactions with Phoenix and would like
> to
> > configure Tephra in HA mode.
> > It seems that one option could be through the
> CFG_DATA_TX_ZOOKEEPER_QUORUM
> > property:
> >
> >
> https://github.com/apache/incubator-tephra/blob/d0a1c4c295fd28e68223db220b13dc1b12b326da/tephra-core/src/main/java/org/apache/tephra/TxConstants.java#L224-L226
> >
> > I've tested this with a couple of Tephra manager processes on different
> > hosts, and they do seem to pass off control as the leader/standby
> > instance.   It's not clear to me though how "in-flight" transactions that
> > have been initiated but not committed yet would be handled during a
> > failover?
> >
> > Is this the recommended approach?  Are the any other settings besides
> > CFG_DATA_TX_ZOOKEEPER_QUORUM that we need to consider?
> >
> > Thank you!
> > Curtis
> >
>

Re: Tephra + Phoenix - configuration for high availability

[Andreas Neumann <an...@apache.org>]

Hi Curtis,

All changes to the transaction state, including in-process transactions,
are captured in the transaction log. When a failover occurs, the new
transaction manager recreates the entire transaction state by replaying the
log from the last snapshot. In-flight transactions should still be able to
commit normally. It could happen, however, that a client rolls back during
the short time that the transaction manager is down. That client would not
be able to notify the tx manager that it has rolled back its transaction.
Such a transaction would time out and become an invalid transaction.

This is tested (not for failover, but for restart) here:
https://github.com/apache/incubator-tephra/blob/master/tephra-core/src/test/java/org/apache/tephra/persist/AbstractTransactionStateStorageTest.java#L124

Cheers -Andreas

On Fri, Nov 9, 2018 at 6:17 AM Curtis Howard <cu...@gmail.com>
wrote:

> Hi,
>
> We are using Tephra to support transactions with Phoenix and would like to
> configure Tephra in HA mode.
> It seems that one option could be through the CFG_DATA_TX_ZOOKEEPER_QUORUM
> property:
>
> https://github.com/apache/incubator-tephra/blob/d0a1c4c295fd28e68223db220b13dc1b12b326da/tephra-core/src/main/java/org/apache/tephra/TxConstants.java#L224-L226
>
> I've tested this with a couple of Tephra manager processes on different
> hosts, and they do seem to pass off control as the leader/standby
> instance.   It's not clear to me though how "in-flight" transactions that
> have been initiated but not committed yet would be handled during a
> failover?
>
> Is this the recommended approach?  Are the any other settings besides
> CFG_DATA_TX_ZOOKEEPER_QUORUM that we need to consider?
>
> Thank you!
> Curtis
>