Streaming Replication

Started by ning chanabout 13 years ago4 messagesgeneral
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#1ning chan
ninchan8328@gmail.com

Hi,
I am new to PG Streaming Replication and I have a simple question hopefully
someone can answer this easily.

I setup a Primary Hot Standby and they are connecting each other without
problem.
Looking at the wal sender process, both servers pointing to the same
location as follow:

Primary:
postgres 3018 0.0 0.1 203888 3024 ? Ss 19:25 0:00 postgres:
wal sender process postgres 10.89.94.31(43169) streaming 0/D913018

Standby:
postgres 3645 0.0 0.1 212556 3096 ? Ss 19:25 0:00 postgres:
wal receiver process streaming 0/D913018

My question is when looking at the standby processes, I see startup process
as follow:

postgres 3320 0.0 0.0 203048 2084 ? Ss 18:11 0:00 postgres:
startup process recovering 00000001000000000000000D

What is that suppose to mean?
Is it really recovering some data from WAL record in the pg_xlog folder?

Thanks~
Ning

#2Laurenz Albe
laurenz.albe@cybertec.at
In reply to: ning chan (#1)
Re: Streaming Replication

ning chan wrote:

I am new to PG Streaming Replication and I have a simple question hopefully someone can answer this
easily.

I setup a Primary Hot Standby and they are connecting each other without problem.
Looking at the wal sender process, both servers pointing to the same location as follow:

Primary:
postgres 3018 0.0 0.1 203888 3024 ? Ss 19:25 0:00 postgres: wal sender process postgres
10.89.94.31(43169) streaming 0/D913018

Standby:
postgres 3645 0.0 0.1 212556 3096 ? Ss 19:25 0:00 postgres: wal receiver process
streaming 0/D913018

My question is when looking at the standby processes, I see startup process as follow:
postgres 3320 0.0 0.0 203048 2084 ? Ss 18:11 0:00 postgres: startup process
recovering 00000001000000000000000D

What is that suppose to mean?
Is it really recovering some data from WAL record in the pg_xlog folder?

That indicates the WAL segment that is currently being
recovered, but not that WAL is read from a file in pg_xlog.

Yours,
Laurenz Albe

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#3ning chan
ninchan8328@gmail.com
In reply to: Laurenz Albe (#2)
Re: Streaming Replication

Hi Albe,
Thanks for your kind response.
The wordings is confusing, it gives me impression that the recovery is
going on.

On Tue, Jan 15, 2013 at 2:09 AM, Albe Laurenz <laurenz.albe@wien.gv.at>wrote:

Show quoted text

ning chan wrote:

I am new to PG Streaming Replication and I have a simple question

hopefully someone can answer this

easily.

I setup a Primary Hot Standby and they are connecting each other without

problem.

Looking at the wal sender process, both servers pointing to the same

location as follow:

Primary:
postgres 3018 0.0 0.1 203888 3024 ? Ss 19:25 0:00

postgres: wal sender process postgres

10.89.94.31(43169) streaming 0/D913018

Standby:
postgres 3645 0.0 0.1 212556 3096 ? Ss 19:25 0:00

postgres: wal receiver process

streaming 0/D913018

My question is when looking at the standby processes, I see startup

process as follow:

postgres 3320 0.0 0.0 203048 2084 ? Ss 18:11 0:00

postgres: startup process

recovering 00000001000000000000000D

What is that suppose to mean?
Is it really recovering some data from WAL record in the pg_xlog folder?

That indicates the WAL segment that is currently being
recovered, but not that WAL is read from a file in pg_xlog.

Yours,
Laurenz Albe

#4Fujii Masao
masao.fujii@gmail.com
In reply to: ning chan (#3)
Re: Streaming Replication

On Wed, Jan 16, 2013 at 1:22 AM, ning chan <ninchan8328@gmail.com> wrote:

Hi Albe,
Thanks for your kind response.
The wordings is confusing, it gives me impression that the recovery is going
on.

Yes. Walreceiver receives the WAL records from the master server, and writes
them to the pg_xlog directory. Then the startup process reads the WAL records
from the pg_xlog directory, and replays them.

Regards,

--
Fujii Masao

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