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Replaces existing legacy documentation.
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FAILOVER.rst
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====================================================
PostgreSQL Automatic Failover - User Documentation
====================================================
Automatic Failover
==================
repmgr allows for automatic failover when it detects the failure of the master node.
Following is a quick setup for this.
Installation
============
For convenience, we define:
**node1**
is the fully qualified domain name of the Master server, IP 192.168.1.10
**node2**
is the fully qualified domain name of the Standby server, IP 192.168.1.11
**witness**
is the fully qualified domain name of the server used as a witness, IP 192.168.1.12
**Note:** We don't recommend using names with the status of a server like «masterserver»,
because it would be confusing once a failover takes place and the Master is
now on the «standbyserver».
Summary
-------
2 PostgreSQL servers are involved in the replication. Automatic failover needs
a vote to decide what server it should promote, so an odd number is required.
A witness-repmgrd is installed in a third server where it uses a PostgreSQL
cluster to communicate with other repmgrd daemons.
1. Install PostgreSQL in all the servers involved (including the witness server)
2. Install repmgr in all the servers involved (including the witness server)
3. Configure the Master PostreSQL
4. Clone the Master to the Standby using "repmgr standby clone" command
5. Configure repmgr in all the servers involved (including the witness server)
6. Register Master and Standby nodes
7. Initiate witness server
8. Start the repmgrd daemons in all nodes
**Note** A complete High-Availability design needs at least 3 servers to still have
a backup node after a first failure.
Install PostgreSQL
------------------
You can install PostgreSQL using any of the recommended methods. You should ensure
it's 9.0 or later.
Install repmgr
--------------
Install repmgr following the steps in the README file.
Configure PostreSQL
-------------------
Log in to node1.
Edit the file postgresql.conf and modify the parameters::
listen_addresses='*'
wal_level = 'hot_standby'
archive_mode = on
archive_command = 'cd .' # we can also use exit 0, anything that
# just does nothing
max_wal_senders = 10
wal_keep_segments = 5000 # 80 GB required on pg_xlog
hot_standby = on
shared_preload_libraries = 'repmgr_funcs'
Edit the file pg_hba.conf and add lines for the replication::
host repmgr repmgr 127.0.0.1/32 trust
host repmgr repmgr 192.168.1.10/30 trust
host replication all 192.168.1.10/30 trust
**Note:** It is also possible to use a password authentication (md5), .pgpass file
should be edited to allow connection between each node.
Create the user and database to manage replication::
su - postgres
createuser -s repmgr
createdb -O repmgr repmgr
Restart the PostgreSQL server::
pg_ctl -D $PGDATA restart
And check everything is fine in the server log.
Create the ssh-key for the postgres user and copy it to other servers::
su - postgres
ssh-keygen # /!\ do not use a passphrase /!\
cat ~/.ssh/id_rsa.pub > ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys
exit
rsync -avz ~postgres/.ssh/authorized_keys node2:~postgres/.ssh/
rsync -avz ~postgres/.ssh/authorized_keys witness:~postgres/.ssh/
rsync -avz ~postgres/.ssh/id_rsa* node2:~postgres/.ssh/
rsync -avz ~postgres/.ssh/id_rsa* witness:~postgres/.ssh/
Clone Master
------------
Log in to node2.
Clone node1 (the current Master)::
su - postgres
repmgr -d repmgr -U repmgr -h node1 standby clone
Start the PostgreSQL server::
pg_ctl -D $PGDATA start
And check everything is fine in the server log.
Configure repmgr
----------------
Log in to each server and configure repmgr by editing the file
/etc/repmgr/repmgr.conf::
cluster=my_cluster
node=1
node_name=earth
conninfo='host=192.168.1.10 dbname=repmgr user=repmgr'
master_response_timeout=60
reconnect_attempts=6
reconnect_interval=10
failover=automatic
promote_command='promote_command.sh'
follow_command='repmgr standby follow -f /etc/repmgr/repmgr.conf'
**cluster**
is the name of the current replication.
**node**
is the number of the current node (1, 2 or 3 in the current example).
**node_name**
is an identifier for every node.
**conninfo**
is used to connect to the local PostgreSQL server (where the configuration file is) from any node. In the witness server configuration you need to add a 'port=5499' to the conninfo.
**master_response_timeout**
is the maximum amount of time we are going to wait before deciding the master has died and start the failover procedure.
**reconnect_attempts**
is the number of times we will try to reconnect to master after a failure has been detected and before start the failover procedure.
**reconnect_interval**
is the amount of time between retries to reconnect to master after a failure has been detected and before start the failover procedure.
**failover**
configure behavior: *manual* or *automatic*.
**promote_command**
the command executed to do the failover (including the PostgreSQL failover itself). The command must return 0 on success.
**follow_command**
the command executed to address the current standby to another Master. The command must return 0 on success.
Register Master and Standby
---------------------------
Log in to node1.
Register the node as master::
su - postgres
repmgr -f /etc/repmgr/repmgr.conf master register
This will also create the repmgr schema and functions.
Log in to node2. Register it as a standby::
su - postgres
repmgr -f /etc/repmgr/repmgr.conf standby register
Initialize witness server
-------------------------
Log in to witness.
Initialize the witness server::
su - postgres
repmgr -d repmgr -U repmgr -h 192.168.1.10 -D $WITNESS_PGDATA -f /etc/repmgr/repmgr.conf witness create
The witness server needs the following information from the command
line:
* Connection details for the current master, to copy the cluster
configuration.
* A location for initializing its own $PGDATA.
repmgr will also ask for the superuser password on the witness database so
it can reconnect when needed (the command line option --initdb-no-pwprompt
will set up a password-less superuser).
By default the witness server will listen on port 5499; this value can be
overridden by explicitly providing the port number in the conninfo string
in repmgr.conf. (Note that it is also possible to specify the port number
with the -l/--local-port option, however this option is now deprecated and
will be overridden by a port setting in the conninfo string).
Start the repmgrd daemons
-------------------------
Log in to node2 and witness::
su - postgres
repmgrd -f /etc/repmgr/repmgr.conf --daemonize -> /var/log/postgresql/repmgr.log 2>&1
**Note:** The Master does not need a repmgrd daemon.
Suspend Automatic behavior
==========================
Edit the repmgr.conf of the node to remove from automatic processing and change::
failover=manual
Then, signal repmgrd daemon::
su - postgres
kill -HUP $(pidof repmgrd)
Usage
=====
The repmgr documentation is in the README file (how to build, options, etc.)

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repmgr quickstart guide
=======================
This quickstart guide provides some annotated examples on basic
`repmgr` setup. It assumes you are familiar with PostgreSQL replication
concepts setup and Linux/UNIX system administration.
For the purposes of this guide, we'll assume the database user will be
`repmgr_usr` and the database will be `repmgr_db`.
Master setup
------------
1. Configure PostgreSQL
- create user and database:
```
CREATE ROLE repmgr_usr LOGIN SUPERUSER;
CREATE DATABASE repmgr_db OWNER repmgr_usr;
```
- configure `postgresql.conf` for replication (see README.md for sample
settings)
- update `pg_hba.conf`, e.g.:
```
host repmgr_db repmgr_usr 192.168.1.0/24 trust
host replication repmgr_usr 192.168.1.0/24 trust
```
Restart the PostgreSQL server after making these changes.
2. Create the `repmgr` configuration file:
$ cat /path/to/repmgr/node1/repmgr.conf
cluster=test
node=1
node_name=node1
conninfo='host=repmgr_node1 user=repmgr_usr dbname=repmgr_db'
pg_bindir=/path/to/postgres/bin
(For an annotated `repmgr.conf` file, see `repmgr.conf.sample` in the
repository's root directory).
3. Register the master node with `repmgr`:
$ repmgr -f /path/to/repmgr/node1/repmgr.conf --verbose master register
[2015-03-03 17:45:53] [INFO] repmgr connecting to master database
[2015-03-03 17:45:53] [INFO] repmgr connected to master, checking its state
[2015-03-03 17:45:53] [INFO] master register: creating database objects inside the repmgr_test schema
[2015-03-03 17:45:53] [NOTICE] Master node correctly registered for cluster test with id 1 (conninfo: host=localhost user=repmgr_usr dbname=repmgr_db)
Standby setup
-------------
1. Use `repmgr standby clone` to clone a standby from the master:
repmgr -D /path/to/standby/data -d repmgr_db -U repmgr_usr --verbose standby clone 192.168.1.2
[2015-03-03 18:18:21] [NOTICE] No configuration file provided and default file './repmgr.conf' not found - continuing with default values
[2015-03-03 18:18:21] [NOTICE] repmgr Destination directory ' /path/to/standby/data' provided
[2015-03-03 18:18:21] [INFO] repmgr connecting to upstream node
[2015-03-03 18:18:21] [INFO] repmgr connected to upstream node, checking its state
[2015-03-03 18:18:21] [INFO] Successfully connected to upstream node. Current installation size is 27 MB
[2015-03-03 18:18:21] [NOTICE] Starting backup...
[2015-03-03 18:18:21] [INFO] creating directory " /path/to/standby/data"...
[2015-03-03 18:18:21] [INFO] Executing: 'pg_basebackup -l "repmgr base backup" -h localhost -p 9595 -U repmgr_usr -D /path/to/standby/data '
NOTICE: pg_stop_backup complete, all required WAL segments have been archived
[2015-03-03 18:18:23] [NOTICE] repmgr standby clone (using pg_basebackup) complete
[2015-03-03 18:18:23] [NOTICE] HINT: You can now start your postgresql server
[2015-03-03 18:18:23] [NOTICE] for example : pg_ctl -D /path/to/standby/data start
Note that the `repmgr.conf` file is not required when cloning a standby.
However we recommend providing a valid `repmgr.conf` if you wish to use
replication slots, or want `repmgr` to log the clone event to the
`repl_events` table.
This will clone the PostgreSQL database files from the master, including its
`postgresql.conf` and `pg_hba.conf` files, and additionally automatically create
the `recovery.conf` file containing the correct parameters to start streaming
from the primary node.
2. Start the PostgreSQL server
3. Create the `repmgr` configuration file:
$ cat /path/node2/repmgr/repmgr.conf
cluster=test
node=2
node_name=node2
conninfo='host=repmgr_node2 user=repmgr_usr dbname=repmgr_db'
pg_bindir=/path/to/postgres/bin
4. Register the standby node with `repmgr`:
$ repmgr -f /path/to/repmgr/node2/repmgr.conf --verbose standby register
[2015-03-03 18:24:34] [NOTICE] Opening configuration file: /path/to/repmgr/node2/repmgr.conf
[2015-03-03 18:24:34] [INFO] repmgr connecting to standby database
[2015-03-03 18:24:34] [INFO] repmgr connecting to master database
[2015-03-03 18:24:34] [INFO] finding node list for cluster 'test'
[2015-03-03 18:24:34] [INFO] checking role of cluster node '1'
[2015-03-03 18:24:34] [INFO] repmgr connected to master, checking its state
[2015-03-03 18:24:34] [INFO] repmgr registering the standby
[2015-03-03 18:24:34] [INFO] repmgr registering the standby complete
[2015-03-03 18:24:34] [NOTICE] Standby node correctly registered for cluster test with id 2 (conninfo: host=localhost user=repmgr_usr dbname=repmgr_db)
This concludes the basic `repmgr` setup of master and standby. The records
created in the `repl_nodes` table should look something like this:
repmgr_db=# SELECT * from repmgr_test.repl_nodes;
id | type | upstream_node_id | cluster | name | conninfo | slot_name | priority | active
----+---------+------------------+---------+-------+----------------------------------------------------+-----------+----------+--------
1 | primary | | test | node1 | host=repmgr_node1 user=repmgr_usr dbname=repmgr_db | | 0 | t
2 | standby | 1 | test | node2 | host=repmgr_node2 user=repmgr_usr dbname=repmgr_db | | 0 | t
(2 rows)

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