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Update FAILOVER.rst

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Ian Barwick
2015-03-26 11:40:51 +09:00
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FAILOVER.rst
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@@ -1,11 +1,11 @@
===================================================== ====================================================
PostgreSQL Automatic Fail-Over - User Documentation PostgreSQL Automatic Failover - User Documentation
===================================================== ====================================================
Automatic Failover Automatic Failover
================== ==================
repmgr allows setups for automatic failover when it detects the failure of the master node. repmgr allows for automatic failover when it detects the failure of the master node.
Following is a quick setup for this. Following is a quick setup for this.
Installation Installation
@@ -14,34 +14,33 @@ Installation
For convenience, we define: For convenience, we define:
**node1** **node1**
is the hostname fully qualified of the Master server, IP 192.168.1.10 is the fully qualified domain name of the Master server, IP 192.168.1.10
**node2** **node2**
is the hostname fully qualified of the Standby server, IP 192.168.1.11 is the fully qualified domain name of the Standby server, IP 192.168.1.11
**witness** **witness**
is the hostname fully qualified of the server used for witness, IP 192.168.1.12 is the fully qualified domain name of the server used as a witness, IP 192.168.1.12
**Note:** It is not recommanded to use name defining status of a server like «masterserver», **Note:** We don't recommend using names with the status of a server like «masterserver»,
this is a name leading to confusion once a failover take place and the Master is because it would be confusing once a failover takes place and the Master is
now on the «standbyserver». now on the «standbyserver».
Summary Summary
------- -------
2 PostgreSQL servers are involved in the replication. Automatic fail-over need 2 PostgreSQL servers are involved in the replication. Automatic failover needs
to vote to decide what server it should promote, thus an odd number is required a vote to decide what server it should promote, so an odd number is required.
and a witness-repmgrd is installed in a third server where it uses a PostgreSQL A witness-repmgrd is installed in a third server where it uses a PostgreSQL
cluster to communicate with other repmgrd daemons. cluster to communicate with other repmgrd daemons.
1. Install PostgreSQL in all the servers involved (including the server used for 1. Install PostgreSQL in all the servers involved (including the witness server)
witness)
2. Install repmgr in all the servers involved (including the server used for witness) 2. Install repmgr in all the servers involved (including the witness server)
3. Configure the Master PostreSQL 3. Configure the Master PostreSQL
4. Clone the Master to the Standby using "repmgr standby clone" command 4. Clone the Master to the Standby using "repmgr standby clone" command
5. Configure repmgr in all the servers involved (including the server used for witness) 5. Configure repmgr in all the servers involved (including the witness server)
6. Register Master and Standby nodes 6. Register Master and Standby nodes
@@ -66,14 +65,14 @@ Install repmgr following the steps in the README file.
Configure PostreSQL Configure PostreSQL
------------------- -------------------
Log in node1. Log in to node1.
Edit the file postgresql.conf and modify the parameters:: Edit the file postgresql.conf and modify the parameters::
listen_addresses='*' listen_addresses='*'
wal_level = 'hot_standby' wal_level = 'hot_standby'
archive_mode = on archive_mode = on
archive_command = 'cd .' # we can also use exit 0, anything that archive_command = 'cd .' # we can also use exit 0, anything that
# just does nothing # just does nothing
max_wal_senders = 10 max_wal_senders = 10
wal_keep_segments = 5000 # 80 GB required on pg_xlog wal_keep_segments = 5000 # 80 GB required on pg_xlog
@@ -117,9 +116,9 @@ Create the ssh-key for the postgres user and copy it to other servers::
Clone Master Clone Master
------------ ------------
Log in node2. Log in to node2.
Clone the node1 (the current Master):: Clone node1 (the current Master)::
su - postgres su - postgres
repmgr -d repmgr -U repmgr -h node1 standby clone repmgr -d repmgr -U repmgr -h node1 standby clone
@@ -133,7 +132,7 @@ And check everything is fine in the server log.
Configure repmgr Configure repmgr
---------------- ----------------
Log in each server and configure repmgr by editing the file Log in to each server and configure repmgr by editing the file
/etc/repmgr/repmgr.conf:: /etc/repmgr/repmgr.conf::
cluster=my_cluster cluster=my_cluster
@@ -154,13 +153,13 @@ Log in each server and configure repmgr by editing the file
**node_name** **node_name**
is an identifier for every node. is an identifier for every node.
**conninfo** **conninfo**
is used to connect to the local PostgreSQL server (where the configuration file is) from any node. In the witness server configuration it is needed to add a 'port=5499' to the 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** **master_response_timeout**
is the maximum amount of time we are going to wait before deciding the master has died and start failover procedure. is the maximum amount of time we are going to wait before deciding the master has died and start the failover procedure.
**reconnect_attempts** **reconnect_attempts**
is the number of times we will try to reconnect to master after a failure has been detected and before start failover procedure. 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** **reconnect_interval**
is the amount of time between retries to reconnect to master after a failure has been detected and before start failover procedure. is the amount of time between retries to reconnect to master after a failure has been detected and before start the failover procedure.
**failover** **failover**
configure behavior: *manual* or *automatic*. configure behavior: *manual* or *automatic*.
**promote_command** **promote_command**
@@ -171,14 +170,14 @@ Log in each server and configure repmgr by editing the file
Register Master and Standby Register Master and Standby
--------------------------- ---------------------------
Log in node1. Log in to node1.
Register the node as Master:: Register the node as Master::
su - postgres su - postgres
repmgr -f /etc/repmgr/repmgr.conf master register repmgr -f /etc/repmgr/repmgr.conf master register
Log in node2. Register it as a standby:: Log in to node2. Register it as a standby::
su - postgres su - postgres
repmgr -f /etc/repmgr/repmgr.conf standby register repmgr -f /etc/repmgr/repmgr.conf standby register
@@ -186,23 +185,30 @@ Log in node2. Register it as a standby::
Initialize witness server Initialize witness server
------------------------- -------------------------
Log in witness. Log in to witness.
Initialize the witness server:: Initialize the witness server::
su - postgres su - postgres
repmgr -d repmgr -U repmgr -h 192.168.1.10 -D $WITNESS_PGDATA -f /etc/repmgr/repmgr.conf witness create repmgr -d repmgr -U repmgr -h 192.168.1.10 -D $WITNESS_PGDATA -f /etc/repmgr/repmgr.conf witness create
It needs information to connect to the master to copy the configuration of the cluster, also it needs to know where it should initialize it's own $PGDATA. The witness server needs the following information from the command
As part of the procees it also ask for the superuser password so it can connect when needed. line:
* Connection details for the current master, to copy the cluster
configuration.
* A location for initializing its own $PGDATA.
It will also ask for the superuser password on the witness database so
it can reconnect when needed.
Start the repmgrd daemons Start the repmgrd daemons
------------------------- -------------------------
Log in node2 and witness. Log in to node2 and witness::
su - postgres su - postgres
repmgrd -f /etc/repmgr/repmgr.conf --daemonize -> /var/log/postgresql/repmgr.log 2>&1 repmgrd -f /etc/repmgr/repmgr.conf --daemonize -> /var/log/postgresql/repmgr.log 2>&1
**Note:** The Master does not need a repmgrd daemon. **Note:** The Master does not need a repmgrd daemon.
@@ -212,12 +218,12 @@ Suspend Automatic behavior
Edit the repmgr.conf of the node to remove from automatic processing and change:: Edit the repmgr.conf of the node to remove from automatic processing and change::
failover=manual failover=manual
Then, signal repmgrd daemon:: Then, signal repmgrd daemon::
su - postgres su - postgres
kill -HUP `pidof repmgrd` kill -HUP $(pidof repmgrd)
Usage Usage
===== =====