...
When a new node is installed, it needs to be connected to the master manually. This can be done with the following script from our tools-repository:
| Code Block |
|---|
| title | Verification commandsLet a new host join the cluster |
|---|
| linenumbers | true |
|---|
|
# postgres-joinMaster.sh <master_host>
Stopping PostgreSQL
Cleaning up old cluster directory
Starting base backup as replicator
pg_basebackup: initiating base backup, waiting for checkpoint to complete
pg_basebackup: checkpoint completed
40842/40842 kB (100%), 1/1 tablespace
NOTICE: WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup
pg_basebackup: base backup completed
Startging PostgreSQL |
WARNING: This script deletes the database on the host where it is run. Do NOT run this script on the master node, as that will cause data loss!
When a node is joined to the cluster it generates a configfile at '/var/lib/postgresql/9.6/main/recovery.conf' which makes this database server connect to that host everytime it starts.
Failover
...
If the primary database server fails hard, and is not coming back a new master needs to be selected. Then the remaining slaves needs to be configured to stream from the new master. After this point, if the old master comes back, it is a seperate database-server (ie: split-brain), and it should thus be configured as a slave server listening to the new master.
Promote slave to master
| Code Block |
|---|
| title | Let a new host join the cluster |
|---|
| linenumbers | true |
|---|
|
root@pgsql1:~# touch /var/lib/postgresql/9.6/main/triggerfile |
Make other slaves follow the new master
| Code Block |
|---|
| title | Let a new host join the cluster |
|---|
| linenumbers | true |
|---|
|
root@pgsql2:~# postgres-joinMaster.sh pgsql1
Stopping PostgreSQL
Cleaning up old cluster directory
Starting base backup as replicator
pg_basebackup: initiating base backup, waiting for checkpoint to complete
pg_basebackup: checkpoint completed
40741/40741 kB (100%), 1/1 tablespace
NOTICE: WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup
pg_basebackup: base backup completed
Add trigger config
Startging PostgreSQL |
Make sure that the keepalive ip for postgres is assigned to the new master
After a new master is selected, make sure the new master is has gotten the postgres IP from keepalived. (In this case it is the IP-address 192.168.254.41)
| Code Block |
|---|
| title | Let a new host join the cluster |
|---|
| linenumbers | true |
|---|
|
root@pgsql1:~# ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens32: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:50:56:8d:1f:aa brd ff:ff:ff:ff:ff:ff
inet 192.168.254.5/26 brd 192.168.254.63 scope global ens32
valid_lft forever preferred_lft forever
inet 192.168.254.41/32 scope global ens32
valid_lft forever preferred_lft forever
inet6 2001:700:1d00:ec10:250:56ff:fe8d:1faa/64 scope global mngtmpaddr dynamic
valid_lft 2591813sec preferred_lft 604613sec
inet6 fe80::250:56ff:fe8d:1faa/64 scope link
valid_lft forever preferred_lft forever |
