repmgr
======

To install repmgr and repmgrd follow this steps:

1) Extract the distribution tar file into the contrib directory of the 
   PostgreSQL distribution sources
2) Check your primary server is correctly configured
3) Write a suitable repmgr.conf for the node
4) Build repmgr programs 
5) Set up trusted copy between postgres accounts (this is only useful for the 
   STANDBY CLONE case)
6) repmgrd additional steps


Extract the distribution tar file 
=================================
cp repmgr.tar.gz ${postgresql_sources}/contrib/. 
cd ${postgresql_sources}/contrib 
tar xvzf repmgr-1.0.tar.gz


Check your primary server configuration
=======================================

PostgreSQL should have been previously built and installed on the system

postgresql.conf
---------------
listen_addresses='*'
wal_level = 'hot_standby'
archive_mode = on
archive_command = 'cd .'	 # we can also use exit 0, anything that just do 
                             # nothing
max_wal_senders = 10
wal_keep_segments = 5000     # 80 GB required on pg_xlog
hot_standby = on

Also you need to add the machines that will participate in the cluster in 
pg_hba.conf. 
NOTE: Is preferred that you have a repmgr user and database and just give 
access to that user, also if you put a password to the user you need to create
a .pgpass file
ie:

host     repmgr           repmgr      10.8.0.0/24         trust
host     replication      all         10.8.0.0/24         trust


Write a suitable repmgr.conf
============================

It should have these three parameters:

1) cluster: A string (single quoted) that identify the cluster we are on 
2) node: An integer that identify our node in the cluster
3) conninfo: A string (single quoted) that teach repmgr how to connect to this 
             node


Build repmgr programs
=====================

make repmgr
make repmgrd

make install (this will put the binaries on the same location as your postgres 
binaries)


Set up trusted copy between postgres accounts
---------------------------------------------

Initial copy between nodes uses the rsync program running over ssh.  For this 
to work, the postgres accounts on each system need to be able to access files 
on their partner node without a password.

First generate a ssh key, using an empty passphrase, and copy the resulting 
keys and a maching authorization file to a privledged user on the other system:

  [postgres@db1]$ ssh-keygen -t rsa
  Generating public/private rsa key pair.
  Enter file in which to save the key (/var/lib/pgsql/.ssh/id_rsa): 
  Enter passphrase (empty for no passphrase): 
  Enter same passphrase again: 
  Your identification has been saved in /var/lib/pgsql/.ssh/id_rsa.
  Your public key has been saved in /var/lib/pgsql/.ssh/id_rsa.pub.
  The key fingerprint is:
  aa:bb:cc:dd:ee:ff:aa:11:22:33:44:55:66:77:88:99 postgres@db1.domain.com
  [postgres@db1]$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
  [postgres@db1]$ chmod go-rwx ~/.ssh/*
  [postgres@db1]$ cd ~/.ssh
  [postgres@db1]$ scp id_rsa.pub id_rsa authorized_keys user@db2:

Login as that user on the other system, and install the files into the postgres 
user's account::

  [user@db2 ~]$ sudo chown postgres.postgres authorized_keys id_rsa.pub id_rsa
  [user@db2 ~]$ sudo mkdir -p ~postgres/.ssh
  [user@db2 ~]$ sudo chown postgres.postgres ~postgres/.ssh
  [user@db2 ~]$ sudo mv authorized_keys id_rsa.pub id_rsa ~postgres/.ssh
  [user@db2 ~]$ sudo chmod -R go-rwx ~postgres/.ssh

Now test that ssh in both directions works (you may have to accept some new 
known hosts in the process)


repmgrd additional steps
========================

To use the repmgrd (repmgr daemon) to monitor standby so we know how is going 
the replication and how far they are from primary, you need to execute the 
repmgr.sql script in the postgres database.

You also need to add a row for every node in the repl_node table