[pgpool-hackers: 2532] Re: New Feature with patch: Quorum and Consensus for backend failover

Tue Sep 12 23:52:08 JST 2017

Hi Ishii-San

On Mon, Sep 11, 2017 at 11:01 AM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> Usama,
>
> I have modified watchdog regression script to test out your quorum
> aware failover patch. Here are differences from the existing script.
>
> - Install streaming replication primary and standby DB node (before
>   raw mode + only 1 node). This is necessary to test an ordinary
>   failover scenario. Current script creates only one DB node. So if we
>   get the node down, the cluster goes into "all db node down"
>   status. I already reported possible problem with the status up
>   thread and waiting for the answer from Usama.
>
> - Add one more pgpool-II node "standby2". For this purpose, new
>   configuration file "standby2.conf" added.
>
> - Add new test scenario: "fake" failover. By using the infrastructure
>   I have created to simulate the communication path between standby2
>   and DB node 1. The test checks if such a error raised a failover
>   request from standby2, but it is safely ignored.
>
> - Add new test scenario: "real" failover. Shutting down DB node 1,
>   which should raise a failover request.
>
> - Modify test.sh to agree with the changes above.
>

Thanks for testing and test script patch. I think the changes and test
scenario is spot on but I think we should add a new test case
with these modifications and keep the 004_watchdog test case in the same
shape as-well, This will help us to identify watchdog issues more
swiftly.

>
> Since the modification requires your quorum patch committed, I haven't
> push the change yet.
>

I was worried about the scenario mentioned above and now identified it as
an existing issue, So will commit the patch tomorrow.

Thanks
Best regardsd
Muhammad Usama

> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
> > I have tested the patch a little bit using 004 watchdog regression
> > test.  After the test ends, I manually started master and standby
> > Pgpool-II.
> >
> > 1) Stop master PostgreSQL. Since there's only one PostgreSQL is
> > configured, I expected:
> >
> > psql: ERROR:  pgpool is not accepting any new connections
> > DETAIL:  all backend nodes are down, pgpool requires at least one valid
> node
> > HINT:  repair the backend nodes and restart pgpool
> >
> > but master Pgpool-II replies:
> >
> > psql: FATAL:  failed to create a backend connection
> > DETAIL:  executing failover on backend
> >
> > Is this normal?
> >
> > 2) I shutdown the master node to see if the standby escalates.
> >
> > After shutting down the master, I see this using pcp_watchdog_info:
> >
> > pcp_watchdog_info -p 11105
> > localhost:11100 Linux tishii-CF-SX3HE4BP localhost 11100 21104 4 MASTER
> > localhost:11000 Linux tishii-CF-SX3HE4BP localhost 11000 21004 10
> SHUTDOWN
> >
> > Seems ok but I want to confirm.
> >
> > master and standby pgpool logs attached.
> >
> > Best regards,
> > --
> > Tatsuo Ishii
> > SRA OSS, Inc. Japan
> > English: http://www.sraoss.co.jp/index_en.php
> > Japanese:http://www.sraoss.co.jp
> >
> >> On Fri, Aug 25, 2017 at 5:05 PM, Tatsuo Ishii <ishii at sraoss.co.jp>
> wrote:
> >>
> >>> > On Fri, Aug 25, 2017 at 12:53 PM, Tatsuo Ishii <ishii at sraoss.co.jp>
> >>> wrote:
> >>> >
> >>> >> Usama,
> >>> >>
> >>> >> With the new patch, the regression tests all passed.
> >>> >>
> >>> >
> >>> > Glad to hear that :-)
> >>> > Did you had a chance to look at the node quarantine state I added.
> What
> >>> are
> >>> > your thoughts on that ?
> >>>
> >>> I'm going to look into the patch this weekend.
> >>>
> >>
> >> Many thanks
> >>
> >> Best Regards
> >> Muhammad Usama
> >>
> >>>
> >>> Best regards,
> >>> --
> >>> Tatsuo Ishii
> >>> SRA OSS, Inc. Japan
> >>> English: http://www.sraoss.co.jp/index_en.php
> >>> Japanese:http://www.sraoss.co.jp
> >>>
> >>> >> > Hi Ishii-San
> >>> >> >
> >>> >> > Please fine the updated patch, It fixes the regression issue you
> were
> >>> >> > facing and also another bug which I encountered during my testing.
> >>> >> >
> >>> >> > -- Adding Yugo to the thread,
> >>> >> > Hi Yugo,
> >>> >> >
> >>> >> > Since you are an expert of watchdog feature, So I thought you
> might
> >>> have
> >>> >> > something to say especially regarding the discussion points
> mentioned
> >>> in
> >>> >> > the initial mail.
> >>> >> >
> >>> >> >
> >>> >> > Thanks
> >>> >> > Best Regards
> >>> >> > Muhammad Usama
> >>> >> >
> >>> >> >
> >>> >> > On Thu, Aug 24, 2017 at 11:25 AM, Muhammad Usama <
> m.usama at gmail.com>
> >>> >> wrote:
> >>> >> >
> >>> >> >>
> >>> >> >>
> >>> >> >> On Thu, Aug 24, 2017 at 4:34 AM, Tatsuo Ishii <
> ishii at sraoss.co.jp>
> >>> >> wrote:
> >>> >> >>
> >>> >> >>> After applying the patch, many of regression tests fail. It
> seems
> >>> >> >>> pgpool.conf.sample has bogus comment which causes the
> pgpool.conf
> >>> >> >>> parser to complain parse error.
> >>> >> >>>
> >>> >> >>> 2017-08-24 08:22:36: pid 6017: FATAL:  syntex error in
> configuration
> >>> >> file
> >>> >> >>> "/home/t-ishii/work/pgpool-II/current/pgpool2/src/test/regre
> >>> >> >>> ssion/tests/004.watchdog/standby/etc/pgpool.conf"
> >>> >> >>> 2017-08-24 08:22:36: pid 6017: DETAIL:  parse error at line 568
> '*'
> >>> >> token
> >>> >> >>> = 8
> >>> >> >>>
> >>> >> >>
> >>> >> >> Really sorry, Somehow I overlooked the sample config file
> changes I
> >>> made
> >>> >> >> at the last minute.
> >>> >> >> Will send you the updated version.
> >>> >> >>
> >>> >> >> Thanks
> >>> >> >> Best Regards
> >>> >> >> Muhammad Usama
> >>> >> >>
> >>> >> >>>
> >>> >> >>> Best regards,
> >>> >> >>> --
> >>> >> >>> Tatsuo Ishii
> >>> >> >>> SRA OSS, Inc. Japan
> >>> >> >>> English: http://www.sraoss.co.jp/index_en.php
> >>> >> >>> Japanese:http://www.sraoss.co.jp
> >>> >> >>>
> >>> >> >>> > Usama,
> >>> >> >>> >
> >>> >> >>> > Thanks for the patch. I am going to review it.
> >>> >> >>> >
> >>> >> >>> > In the mean time when I apply your patch, I got some trailing
> >>> >> >>> > whitespace errors. Can you please fix them?
> >>> >> >>> >
> >>> >> >>> > /home/t-ishii/quorum_aware_failover.diff:470: trailing
> >>> whitespace.
> >>> >> >>> >
> >>> >> >>> > /home/t-ishii/quorum_aware_failover.diff:485: trailing
> >>> whitespace.
> >>> >> >>> >
> >>> >> >>> > /home/t-ishii/quorum_aware_failover.diff:564: trailing
> >>> whitespace.
> >>> >> >>> >
> >>> >> >>> > /home/t-ishii/quorum_aware_failover.diff:1428: trailing
> >>> whitespace.
> >>> >> >>> >
> >>> >> >>> > /home/t-ishii/quorum_aware_failover.diff:1450: trailing
> >>> whitespace.
> >>> >> >>> >
> >>> >> >>> > warning: squelched 3 whitespace errors
> >>> >> >>> > warning: 8 lines add whitespace errors.
> >>> >> >>> >
> >>> >> >>> > Best regards,
> >>> >> >>> > --
> >>> >> >>> > Tatsuo Ishii
> >>> >> >>> > SRA OSS, Inc. Japan
> >>> >> >>> > English: http://www.sraoss.co.jp/index_en.php
> >>> >> >>> > Japanese:http://www.sraoss.co.jp
> >>> >> >>> >
> >>> >> >>> >> Hi
> >>> >> >>> >>
> >>> >> >>> >> I was working on the new feature to make the backend node
> >>> failover
> >>> >> >>> quorum
> >>> >> >>> >> aware and on the half way through the implementation I also
> added
> >>> >> the
> >>> >> >>> >> majority consensus feature for the same.
> >>> >> >>> >>
> >>> >> >>> >> So please find the first version of the patch for review that
> >>> makes
> >>> >> the
> >>> >> >>> >> backend node failover consider the watchdog cluster quorum
> status
> >>> >> and
> >>> >> >>> seek
> >>> >> >>> >> the majority consensus before performing failover.
> >>> >> >>> >>
> >>> >> >>> >> *Changes in the Failover mechanism with watchdog.*
> >>> >> >>> >> For this new feature I have modified the Pgpool-II's existing
> >>> >> failover
> >>> >> >>> >> mechanism with watchdog.
> >>> >> >>> >> Previously as you know when the Pgpool-II require to perform
> a
> >>> node
> >>> >> >>> >> operation (failover, failback, promote-node) with the
> watchdog.
> >>> The
> >>> >> >>> >> watchdog used to propagated the failover request to all the
> >>> >> Pgpool-II
> >>> >> >>> nodes
> >>> >> >>> >> in the watchdog cluster and as soon as the request was
> received
> >>> by
> >>> >> the
> >>> >> >>> >> node, it used to initiate the local failover and that
> failover
> >>> was
> >>> >> >>> >> synchronised on all nodes using the distributed locks.
> >>> >> >>> >>
> >>> >> >>> >> *Now Only the Master node performs the failover.*
> >>> >> >>> >> The attached patch changes the mechanism of synchronised
> >>> failover,
> >>> >> and
> >>> >> >>> now
> >>> >> >>> >> only the Pgpool-II of master watchdog node performs the
> failover,
> >>> >> and
> >>> >> >>> all
> >>> >> >>> >> other standby nodes sync the backend statuses after the
> master
> >>> >> >>> Pgpool-II is
> >>> >> >>> >> finished with the failover.
> >>> >> >>> >>
> >>> >> >>> >> *Overview of new failover mechanism.*
> >>> >> >>> >> -- If the failover request is received to the standby
> watchdog
> >>> >> >>> node(from
> >>> >> >>> >> local Pgpool-II), That request is forwarded to the master
> >>> watchdog
> >>> >> and
> >>> >> >>> the
> >>> >> >>> >> Pgpool-II main process is returned with the
> >>> >> FAILOVER_RES_WILL_BE_DONE
> >>> >> >>> >> return code. And upon receiving the FAILOVER_RES_WILL_BE_DONE
> >>> from
> >>> >> the
> >>> >> >>> >> watchdog for the failover request the requesting Pgpool-II
> moves
> >>> >> >>> forward
> >>> >> >>> >> without doing anything further for the particular failover
> >>> command.
> >>> >> >>> >>
> >>> >> >>> >> -- Now when the failover request from standby node is
> received by
> >>> >> the
> >>> >> >>> >> master watchdog, after performing the validation, applying
> the
> >>> >> >>> consensus
> >>> >> >>> >> rules the failover request is triggered on the local
> Pgpool-II .
> >>> >> >>> >>
> >>> >> >>> >> -- When the failover request is received to the master
> watchdog
> >>> node
> >>> >> >>> from
> >>> >> >>> >> the local Pgpool-II (On the IPC channel) the watchdog process
> >>> inform
> >>> >> >>> the
> >>> >> >>> >> Pgpool-II requesting process to proceed with failover
> (provided
> >>> all
> >>> >> >>> >> failover rules are satisfied).
> >>> >> >>> >>
> >>> >> >>> >> -- After the failover is finished on the master Pgpool-II,
> the
> >>> >> failover
> >>> >> >>> >> function calls the *wd_failover_end*() which sends the
> backend
> >>> sync
> >>> >> >>> >> required message to all standby watchdogs.
> >>> >> >>> >>
> >>> >> >>> >> -- Upon receiving the sync required message from master
> watchdog
> >>> >> node
> >>> >> >>> all
> >>> >> >>> >> Pgpool-II sync the new statuses of each backend node from the
> >>> master
> >>> >> >>> >> watchdog.
> >>> >> >>> >>
> >>> >> >>> >> *No More Failover locks*
> >>> >> >>> >> Since with this new failover mechanism we do not require any
> >>> >> >>> >> synchronisation and guards against the execution of
> >>> >> failover_commands
> >>> >> >>> by
> >>> >> >>> >> multiple Pgpool-II nodes, So the patch removes all the
> >>> distributed
> >>> >> >>> locks
> >>> >> >>> >> from failover function, This makes the failover simpler and
> >>> faster.
> >>> >> >>> >>
> >>> >> >>> >> *New kind of Failover operation NODE_QUARANTINE_REQUEST*
> >>> >> >>> >> The patch adds the new kind of backend node operation
> >>> >> NODE_QUARANTINE
> >>> >> >>> which
> >>> >> >>> >> is effectively same as the NODE_DOWN, but with
> node_quarantine
> >>> the
> >>> >> >>> >> failover_command is not triggered.
> >>> >> >>> >> The NODE_DOWN_REQUEST is automatically converted to the
> >>> >> >>> >> NODE_QUARANTINE_REQUEST when the failover is requested on the
> >>> >> backend
> >>> >> >>> node
> >>> >> >>> >> but watchdog cluster does not holds the quorum.
> >>> >> >>> >> This means in the absence of quorum the failed backend nodes
> are
> >>> >> >>> >> quarantined and when the quorum becomes available again the
> >>> >> Pgpool-II
> >>> >> >>> >> performs the failback operation on all quarantine nodes.
> >>> >> >>> >> And again when the failback is performed on the quarantine
> >>> backend
> >>> >> >>> node the
> >>> >> >>> >> failover function does not trigger the failback_command.
> >>> >> >>> >>
> >>> >> >>> >> *Controlling the Failover behaviour.*
> >>> >> >>> >> The patch adds three new configuration parameters to
> configure
> >>> the
> >>> >> >>> failover
> >>> >> >>> >> behaviour from user side.
> >>> >> >>> >>
> >>> >> >>> >> *failover_when_quorum_exists*
> >>> >> >>> >> When enabled the failover command will only be executed when
> the
> >>> >> >>> watchdog
> >>> >> >>> >> cluster holds the quorum. And when the quorum is absent and
> >>> >> >>> >> failover_when_quorum_exists is enabled the failed backend
> nodes
> >>> will
> >>> >> >>> get
> >>> >> >>> >> quarantine until the quorum becomes available again.
> >>> >> >>> >> disabling it will enable the old behaviour of failover
> commands.
> >>> >> >>> >>
> >>> >> >>> >>
> >>> >> >>> >> *failover_require_consensus*This new configuration parameter
> >>> can be
> >>> >> >>> used to
> >>> >> >>> >> make sure we get the majority vote before performing the
> >>> failover on
> >>> >> >>> the
> >>> >> >>> >> node. When *failover_require_consensus* is enabled then the
> >>> >> failover is
> >>> >> >>> >> only performed after receiving the failover request from the
> >>> >> majority
> >>> >> >>> or
> >>> >> >>> >> Pgpool-II nodes.
> >>> >> >>> >> For example in three nodes cluster the failover will not be
> >>> >> performed
> >>> >> >>> until
> >>> >> >>> >> at least two nodes ask for performing the failover on the
> >>> particular
> >>> >> >>> >> backend node.
> >>> >> >>> >>
> >>> >> >>> >> It is also worthwhile to mention here that
> >>> >> *failover_require_consensus*
> >>> >> >>> >> only works when failover_when_quorum_exists is enables.
> >>> >> >>> >>
> >>> >> >>> >>
> >>> >> >>> >> *enable_multiple_failover_requests_from_node*
> >>> >> >>> >> This parameter works in connection with
> >>> *failover_require_consensus*
> >>> >> >>> >> config. When enabled a single Pgpool-II node can vote for
> >>> failover
> >>> >> >>> multiple
> >>> >> >>> >> times.
> >>> >> >>> >> For example in the three nodes cluster if one Pgpool-II node
> >>> sends
> >>> >> the
> >>> >> >>> >> failover request of particular node twice that would be
> counted
> >>> as
> >>> >> two
> >>> >> >>> >> votes in favour of failover and the failover will be
> performed
> >>> even
> >>> >> if
> >>> >> >>> we
> >>> >> >>> >> do not get a vote from other two nodes.
> >>> >> >>> >>
> >>> >> >>> >> And when *enable_multiple_failover_requests_from_node* is
> >>> disabled,
> >>> >> >>> Only
> >>> >> >>> >> the first vote from each Pgpool-II will be accepted and all
> other
> >>> >> >>> >> subsequent votes will be marked duplicate and rejected.
> >>> >> >>> >> So in that case we will require a majority votes from
> distinct
> >>> >> nodes to
> >>> >> >>> >> execute the failover.
> >>> >> >>> >> Again this *enable_multiple_failover_requests_from_node*
> only
> >>> >> becomes
> >>> >> >>> >> effective when both *failover_when_quorum_exists* and
> >>> >> >>> >> *failover_require_consensus* are enabled.
> >>> >> >>> >>
> >>> >> >>> >>
> >>> >> >>> >> *Controlling the failover: The Coding perspective.*
> >>> >> >>> >> Although the failover functions are made quorum and consensus
> >>> aware
> >>> >> but
> >>> >> >>> >> there is still a way to bypass the quorum conditions, and
> >>> >> requirement
> >>> >> >>> of
> >>> >> >>> >> consensus.
> >>> >> >>> >>
> >>> >> >>> >> For this the patch uses the existing request_details flags in
> >>> >> >>> >> POOL_REQUEST_NODE to control the behaviour of failover.
> >>> >> >>> >>
> >>> >> >>> >> Here are the newly added flags values.
> >>> >> >>> >>
> >>> >> >>> >> *REQ_DETAIL_WATCHDOG*:
> >>> >> >>> >> Setting this flag while issuing the failover command will not
> >>> send
> >>> >> the
> >>> >> >>> >> failover request to the watchdog. But this flag may not be
> >>> useful in
> >>> >> >>> any
> >>> >> >>> >> other place than where it is already used.
> >>> >> >>> >> Mostly this flag can be used to avoid the failover command
> from
> >>> >> going
> >>> >> >>> to
> >>> >> >>> >> watchdog that is already originated from watchdog. Otherwise
> we
> >>> can
> >>> >> >>> end up
> >>> >> >>> >> in infinite loop.
> >>> >> >>> >>
> >>> >> >>> >> *REQ_DETAIL_CONFIRMED*:
> >>> >> >>> >> Setting this flag will bypass the
> *failover_require_consensus*
> >>> >> >>> >> configuration and immediately perform the failover if quorum
> is
> >>> >> >>> present.
> >>> >> >>> >> This flag can be used to issue the failover request
> originated
> >>> from
> >>> >> PCP
> >>> >> >>> >> command.
> >>> >> >>> >>
> >>> >> >>> >> *REQ_DETAIL_UPDATE*:
> >>> >> >>> >> This flag is used for the command where we are failing back
> the
> >>> >> >>> quarantine
> >>> >> >>> >> nodes. Setting this flag will not trigger the
> failback_command.
> >>> >> >>> >>
> >>> >> >>> >> *Some conditional flags used:*
> >>> >> >>> >> I was not sure about the configuration of each type of
> failover
> >>> >> >>> operation.
> >>> >> >>> >> As we have three main failover operations NODE_UP_REQUEST,
> >>> >> >>> >> NODE_DOWN_REQUEST, and PROMOTE_NODE_REQUEST
> >>> >> >>> >> So I was thinking do we need to give the configuration
> option to
> >>> the
> >>> >> >>> users,
> >>> >> >>> >> if they want to enable/disable quorum checking and consensus
> for
> >>> >> >>> individual
> >>> >> >>> >> failover operation type.
> >>> >> >>> >> For example: is it a practical configuration where a user
> would
> >>> >> want to
> >>> >> >>> >> ensure quorum while preforming NODE_DOWN operation while
> does not
> >>> >> want
> >>> >> >>> it
> >>> >> >>> >> for NODE_UP.
> >>> >> >>> >> So in this patch I use three compile time defines to enable
> >>> disable
> >>> >> the
> >>> >> >>> >> individual failover operation, while we can decide on the
> best
> >>> >> >>> solution.
> >>> >> >>> >>
> >>> >> >>> >> NODE_UP_REQUIRE_CONSENSUS: defining it will enable quorum
> >>> checking
> >>> >> >>> feature
> >>> >> >>> >> for NODE_UP_REQUESTs
> >>> >> >>> >>
> >>> >> >>> >> NODE_DOWN_REQUIRE_CONSENSUS: defining it will enable quorum
> >>> checking
> >>> >> >>> >> feature for NODE_DOWN_REQUESTs
> >>> >> >>> >>
> >>> >> >>> >> NODE_PROMOTE_REQUIRE_CONSENSUS: defining it will enable
> quorum
> >>> >> >>> checking
> >>> >> >>> >> feature for PROMOTE_NODE_REQUESTs
> >>> >> >>> >>
> >>> >> >>> >> *Some Point for Discussion:*
> >>> >> >>> >>
> >>> >> >>> >> *Do we really need to check ReqInfo->switching flag before
> >>> enqueuing
> >>> >> >>> >> failover request.*
> >>> >> >>> >> While working on the patch I was wondering why do we disallow
> >>> >> >>> enqueuing the
> >>> >> >>> >> failover command when the failover is already in progress?
> For
> >>> >> example
> >>> >> >>> in
> >>> >> >>> >> *pcp_process_command*() function if we see the
> >>> *Req_info->switching*
> >>> >> >>> flag
> >>> >> >>> >> set we bailout with the error instead of enqueuing the
> command.
> >>> Is
> >>> >> is
> >>> >> >>> >> really necessary?
> >>> >> >>> >>
> >>> >> >>> >> *Do we need more granule control over each failover
> operation:*
> >>> >> >>> >> As described in section "Some conditional flags used" I want
> the
> >>> >> >>> opinion on
> >>> >> >>> >> do we need configuration parameters in pgpool.conf to enable
> >>> disable
> >>> >> >>> quorum
> >>> >> >>> >> and consensus checking on individual failover types.
> >>> >> >>> >>
> >>> >> >>> >> *Which failover should be mark as Confirmed:*
> >>> >> >>> >> As defined in the above section of REQ_DETAIL_CONFIRMED, We
> can
> >>> mark
> >>> >> >>> the
> >>> >> >>> >> failover request to not need consensus, currently the
> requests
> >>> from
> >>> >> >>> the PCP
> >>> >> >>> >> commands are fired with this flag. But I was wondering there
> may
> >>> be
> >>> >> >>> more
> >>> >> >>> >> places where we many need to use the flag.
> >>> >> >>> >> For example I currently use the same confirmed flag when
> >>> failover is
> >>> >> >>> >> triggered because of *replication_stop_on_mismatch*.
> >>> >> >>> >>
> >>> >> >>> >> I think we should think this flag for each place of failover,
> >>> like
> >>> >> >>> when the
> >>> >> >>> >> failover is triggered
> >>> >> >>> >> because of health_check failure.
> >>> >> >>> >> because of replication mismatch
> >>> >> >>> >> because of backend_error
> >>> >> >>> >> e.t.c
> >>> >> >>> >>
> >>> >> >>> >> *Node Quarantine behaviour.*
> >>> >> >>> >> What do you think about the node quarantine used by this
> patch.
> >>> Can
> >>> >> you
> >>> >> >>> >> think of some problem which can be caused by this?
> >>> >> >>> >>
> >>> >> >>> >> *What should be the default values for each newly added
> config
> >>> >> >>> parameters.*
> >>> >> >>> >>
> >>> >> >>> >>
> >>> >> >>> >>
> >>> >> >>> >> *TODOs*
> >>> >> >>> >>
> >>> >> >>> >> -- Updating the documentation is still todo. Will do that
> once
> >>> every
> >>> >> >>> aspect
> >>> >> >>> >> of the feature will be finalised.
> >>> >> >>> >> -- Some code warnings and cleanups are still not done.
> >>> >> >>> >> -- I am still little short on testing
> >>> >> >>> >> -- Regression test cases for the feature
> >>> >> >>> >>
> >>> >> >>> >>
> >>> >> >>> >> Thoughts and suggestions are most welcome.
> >>> >> >>> >>
> >>> >> >>> >> Thanks
> >>> >> >>> >> Best regards
> >>> >> >>> >> Muhammad Usama
> >>> >> >>> > _______________________________________________
> >>> >> >>> > pgpool-hackers mailing list
> >>> >> >>> > pgpool-hackers at pgpool.net
> >>> >> >>> > http://www.pgpool.net/mailman/listinfo/pgpool-hackers
> >>> >> >>>
> >>> >> >>
> >>> >> >>
> >>> >>
> >>>
>
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