Re: Running Multiple Postmasters

["Joshua D. Drake" <jd@commandprompt.com>]

Hello,

We do it all the time at Command Prompt. That is how we do the managed shared hosting. Every customer gets a private
data directory that is on its own TCP port.

J


Clay Luther wrote:

I am wondering if it is possible, or even advisable, to run two postmasters on a single system.

 

For example, we have an embedded system with a normal runtime partition (called the "A") in which the PGDATA is /var/lib/pgsql/data. We also have a offline partition which is a copy of the runtime partition, but is mounted under /partB -- PGDATA here is /partB/var/lib/pgsql/data.

 

During upgrades, we will alter the installation on the B partition, then swap the paritions after a reboot.

 

However, during upgrades, we may need to migrate data from the A partition databases to the B partition databases.

 

For database migrations, I was hoping I could do the following (remember, a postmaster is already running on /var/lib/pgsql/data):

 

1) Alter the the postgresql.conf of the B partition PGDATA, setting the tcp/ip port to 54321.

2) Start the "B" postmaster, pg_ctl -D /partB/var/lib/pgsql/data start

3) Use ODBC/JDBC to perform necessary migration from A databases to B databases.

4) pg_ctl -D /partB/var/lib/pgsql/data stop

5) Set B postgresql.conf tcp/ip port to 5432.

6) Reboot (higher level systems will automatically swap the A and B partitions, so B becomes A and A becomes the new B).

 

Conceptually clear, but I wanted to know if there was anything I needed to be worried about.

 

Thanks.

 

---

Clay

claycle@cisco.com

(972) 813-5004

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