Re: How to do failover in pglogical replication?

From: roshan_myrepublic <roshan(at)myrepublic(dot)net>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: How to do failover in pglogical replication?
Date: 2016-08-24 11:42:39
Message-ID: CAHtY=o6AzTnqdjRP2SzSx3ze_bXRaPzKzKZ_G7cKPiQLu9WRKA@mail.gmail.com
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Hi Craig,

I am trying to set up pglogical replication. I have a table which has
around 4 rows in the provider server.
=========
employee_id | visitor_email | vistor_id | date |
message
-------------+-----------------------+-----------+---------------------+--------------------------
1 | roshan(at)gmail(dot)com | 1 | 2016-08-24 00:00:00 |
This is the first test.
2 | roshan(at)myrepublic(dot)net | 2 | 2016-08-24 00:00:00 |
This is the second test.
3 | roshan(at)myrepublic(dot)net | 3 | 2016-08-24 00:00:00 |
This is the third test.
4 | roshan(at)myrepublic(dot)net | 4 | 2016-08-24 00:00:00 |
This is the fourth test.
===============================

After creating the above mentioned table. I have created a replication set
in the provider . Then I configured the subscriber node and the
subscription. Ideally, I should see the 4 rows from the provider table in
my subscriber, but I am only seeing the table structure in subscriber, not
the data. If I add a new row in the provider table as follows

INSERT INTO employees (employee_id, visitor_email, date, message) VALUES
(4, 'roshan(at)myrepublic(dot)net', current_date, 'This is the fourth test.');

Now, I am able to see the last added row in my subscriber table. All the
other 4 rows which were added in the beginning are still missing. What am I
doing wrong here?

Does it mean that only the data which was created after the creation of
replication_sets will be considered? How to add the whole content of a
table to a replication set.?

Any help would be much appreciated.?

Regards,
Muhammed Roshan

On Thu, Aug 18, 2016 at 1:01 PM, Craig Ringer-3 [via PostgreSQL] <
ml-node+s1045698n5916916h64(at)n5(dot)nabble(dot)com> wrote:

> On 17 August 2016 at 18:21, roshan_myrepublic <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=5916916&i=0>> wrote:
>
>> Hi,
>>
>> I am currently exploring pglogical replication for my db servers. I would
>> like to know how can I automatically failover from Provider Node to
>> Subscriber Node, if the Provider node goes down for some reasons. How can
>> I
>> redirect all the traffic to SubscriberNode automatically ? In the normal
>> replication, we use recovery_file and triggers to get this job done. Do we
>> have any similar alternative for pglogical replications as well?
>
>
> There is not, as yet, any integegration into tooling like repmgr. You'll
> want some fairly simple scripts to manage failover, likely:
>
> * Update pgbouncer / haproxy / whatever to redirect connections
> * Drop the subscription on the replica
> * STONITH to make sure the master is really down
> * Clone and start a new master
>
> There's some work on automating this through repmgr, but at this time
> pglogical isn't really focused on failover deployments as its main use
> case. The limitations in PostgreSQL's logical decoding and replication when
> it comes to handling of big xacts, sequences, etc mean it's still better
> suited to data movement/integration etc than HA.
>
> --
> Craig Ringer http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training & Services
>
>
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