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| Deletions are marked like this. | Additions are marked like this. |
| Line 1: | Line 1: |
| INCOMPLETE DO NOT USE |
|
| Line 7: | Line 5: |
| * 192.168.1.58 redis01 * 192.168.1.59 redis02 * 192.168.1.60 redis03 |
* 192.168.1.59 redis01 (master) * 192.168.1.60 redis02 (replica) * 192.168.1.61 redis03 (replica) |
| Line 21: | Line 19: |
| Make sure the apache servers can reach redis. Change `bind 127.0.0.1` in `/etc/redis/redis.conf`. Each of the redis servers needs to listen on its own IP-address. | Change the contents of the redis configuration file in `/etc/redis/redis.conf`. |
| Line 23: | Line 21: |
| Add the IP-address for each of the servers. Each of the redis servers needs to listen on its own IP-address. | |
| Line 24: | Line 23: |
| bind 127.0.0.1 192.168.1.58 | bind 192.168.1.59 127.0.0.1 ::1 |
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| Stop the redis server on all hosts. | Enable redis to listen on the network, instead of only listening on the loopback device. {{{ protected-mode no }}} Now restart the redis master {{{ service redis-server restart }}} And stop the replicas |
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| To enable replication we need to consider one of the redis servers the master. Here it will be redis01. On the two other hosts add the following to `/etc/redis/redis.conf`. | On each of the replicas, set them up af a replica of the master |
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| slaveof 192.168.1.58 6379 | replicaof 192.168.1.59 6379 |
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| Start the redis servers again, but start it on redis01 first. | Start the replicas again |
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| service redis-server start | services redis-server start |
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| redis01 should now be the master. | |
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| === Redis Sentinel === The same goes for `/etc/redis/sentinel.conf` |
You should now be able to see the replicas from the master `redis-cli -h 192.168.1.59`. |
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| bind 127.0.0.1 192.168.1.58 | 192.168.1.59:6379> info replication # Replication role:master connected_slaves:2 slave0:ip=192.168.1.60,port=6379,state=online,offset=2615,lag=0 slave1:ip=192.168.1.61,port=6379,state=online,offset=2615,lag=1 master_replid:79a21f08669303e71990ea8819830f30c94384c6 master_replid2:0000000000000000000000000000000000000000 master_repl_offset:2615 second_repl_offset:-1 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:1 repl_backlog_histlen:2615 |
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| * https://www.haproxy.com/blog/haproxy-advanced-redis-health-check/ | |
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| * https://blog.usejournal.com/first-step-to-redis-cluster-7712e1c31847 * https://www.linode.com/docs/applications/big-data/how-to-install-and-configure-a-redis-cluster-on-ubuntu-1604/ * https://www.willandskill.se/en/setup-a-highly-available-redis-cluster-with-sentinel-and-haproxy/ * https://www.tecmint.com/setup-redis-replication-in-centos-8/ * https://www.tecmint.com/setup-redis-high-availability-with-sentinel-in-centos-8/ * https://www.tecmint.com/setup-redis-cluster-in-centos-8/ * https://stackoverflow.com/questions/39568561/how-to-solve-redis-cluster-waiting-for-the-cluster-to-join-issue |
Redis
Redis is an in memory data structure storage. It will be used to share PHP-sessions between the apache servers. To guarantee a robust deployment three redis servers will be configured.
- 192.168.1.59 redis01 (master)
- 192.168.1.60 redis02 (replica)
- 192.168.1.61 redis03 (replica)
Software
apt-get install redis-server redis-sentinel
Configuration
Redis Server
Change the contents of the redis configuration file in /etc/redis/redis.conf.
Add the IP-address for each of the servers. Each of the redis servers needs to listen on its own IP-address.
bind 192.168.1.59 127.0.0.1 ::1
Enable redis to listen on the network, instead of only listening on the loopback device.
protected-mode no
Now restart the redis master
service redis-server restart
And stop the replicas
service redis-server stop
On each of the replicas, set them up af a replica of the master
replicaof 192.168.1.59 6379
Start the replicas again
services redis-server start
You should now be able to see the replicas from the master redis-cli -h 192.168.1.59.
192.168.1.59:6379> info replication # Replication role:master connected_slaves:2 slave0:ip=192.168.1.60,port=6379,state=online,offset=2615,lag=0 slave1:ip=192.168.1.61,port=6379,state=online,offset=2615,lag=1 master_replid:79a21f08669303e71990ea8819830f30c94384c6 master_replid2:0000000000000000000000000000000000000000 master_repl_offset:2615 second_repl_offset:-1 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:1 repl_backlog_histlen:2615
References
https://www.haproxy.com/blog/haproxy-advanced-redis-health-check/
https://blog.usejournal.com/first-step-to-redis-cluster-7712e1c31847
https://www.willandskill.se/en/setup-a-highly-available-redis-cluster-with-sentinel-and-haproxy/
https://www.tecmint.com/setup-redis-replication-in-centos-8/
https://www.tecmint.com/setup-redis-high-availability-with-sentinel-in-centos-8/