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Synch Replication - Synch rep 0114

From

"Patil, Smita (NSN - IN/Bangalore)"

Date:

30 January 2009, 10:48:24

Hi,

I have been testing in recent, the Synch Replication(Synch rep 0114 (Jan 14, 2009) ) on PostgreSQL version 8.4 (

postgresql-8.4devel_20081229.tar.bz2)

I followed the steps in Readme as well used the test script provided in patch for the setup.

As per wiki, I am able to bring up the walsender and the walreceiver process in a single server as well when primary and seconday are setup on different nodes(making necessary changes to the test script)

Then I am able to see the walsender and walreceiver process are in progress.

Then I try to insert some records into the table created (within the script) as below:

./psql
psql (8.4devel)
Type "help" for help.

postgres=# insert into temp values(5,'e');

I get the following output :

Standby 6820 FATAL: unexpected EOF on replication connection: lost synchronization with server: got message type "c", length -805175295

Primary 6821 LOG: unexpected EOF on replication connection
Primary 6821 LOG: replication done at: write 0/1000000 (file 000000010000000000000000), flush 0/1000000 (file 000000010000000000000000)
Standby 6820 LOG: replication done at: write 0/1000000 (file 000000010000000000000000), flush 0/1000000 (file 000000010000000000000000)
Standby 6812 LOG: could not open file "pg_xlog/000000010000000000000001" (log file 0, segment 1): No such file or directory
Standby 6812 LOG: redo done at 0/4A983C
Standby 6812 PANIC: could not open file "pg_xlog/000000010000000000000000" (log file 0, segment 0): No such file or directory
Standby 6809 LOG: startup process (PID 6812) was terminated by signal 6: Aborted
Standby 6809 LOG: aborting startup due to startup process failure
INSERT 0 1

After this, I see both walsender and walreceiver are down and writer process is still running.

Is this because, there is no provision of replication between primary and secondary?

Or is it because write transactions are not supported?

In case where primary and standby are run on two different nodes, I am able to bring up the walsender and walreceiver process.

But atleast read transactions( records inserted in primary ) are not getting reflected in the standby node.

In such cases I would like to know about what exact features are working with this patch?

Because, in the Readme section of Synch Replication wiki, it is mentioned to check whether the walsender and walreceiver process are in progress.

How about replication and read - write transactions?

Also with the latest patch Synch rep 0128 (Jan 28, 2009), Am getting compilation errors.

Please let me about the correct status of the Synch Replication about what features are working properly.

Regards,
Smita Patil

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Re: Synch Replication - Synch rep 0114

From

Fujii Masao

Date:

30 January 2009, 11:17:57

Hi,

On Fri, Jan 30, 2009 at 8:05 PM, Patil, Smita (NSN - IN/Bangalore)
<smita.patil@nsn.com> wrote:
> Hi,
> I have been testing in recent, the Synch Replication(Synch rep 0114 (Jan 14,
> 2009) ) on PostgreSQL version 8.4 (
> postgresql-8.4devel_20081229.tar.bz2)

Thanks for your testing and report!

I'm afraid that the base HEAD version
(postgresql-8.4devel_20081229.tar.bz2) is old,
which might have caused the following error. So, please try to apply
synch-rep v0128
patch to the latest HEAD, and test it.

If you can use cvs, the following document might be helpful for you to
get the latest HEAD.
http://www.postgresql.org/docs/8.3/static/anoncvs.html

> As per wiki, I am able to bring up the walsender and the walreceiver process
> in a single server as well when primary and seconday are setup on different
> nodes(making necessary changes to the test script)

What kind of change was required?

> Then I am able to see the walsender and walreceiver process are in progress.

Good!

> Then I try to insert some records into the table created (within the script)
> as below:
> ./psql
> psql (8.4devel)
> Type "help" for help.
>
> postgres=# insert into temp values(5,'e');

Please let me know the DDL of creating "temp" table. I'll test it also on
my machine.

> After this, I see both walsender and walreceiver are down and writer process
> is still running.
> Is this because, there is no provision of replication between primary and
> secondary?

Yes, it's because unexpected error terminated replication (ie. walsender
and walreceiver). But, such termination of replication doesn't affect the
primary's normal processing, so walwriter was still running on the primary.

> Or is it because write transactions are not supported?

Write transactions are also supported like original postgres.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

Synch Replication

From

"K, Niranjan (NSN - IN/Bangalore)"

Date:

03 February 2009, 10:57:18

Hi,

I tried using the Synchronous replication and I'am unable to replicate
the queries (Ex. create table temp1(int int);).

I have downloaded the latest postgres dev snapshot and the latest sync
replication patch from wiki.

I have attached the log file which has the trace statements displayed on
the console. I actually changed the 'test_synch_rep.sh', so that the
standby database will put detailed trace messages.

I'am actaully getting error related to history file.

Could you please help regarding this.

regards,
Niranjan