Guide pour faire du master/replica surveillé par HAProxy
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HowtoRedis.md
166
HowtoRedis.md
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@ -423,6 +423,172 @@ Sentinel doit pouvoir ecrire dans son fichier de configuration :
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chown redis: /etc/redis/sentinel.conf
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~~~
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## Load-balancing avec HAProxy
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Il est possible d'avoir un master et plusieurs replica derrière un proxy/load-balancer HAProxy (sur `172.19.3.100` dans l'exemple).
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~~~.haproxy
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frontend fe_redis
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mode tcp
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option tcplog
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bind 127.0.0.1:6379
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default_backend be_redis
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backend be_redis
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mode tcp
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balance first
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default-server maxconn 1024 check agent-check agent-port 16379 agent-inter 1s
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server srv1 172.20.3.200:6379
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server srv2 172.20.3.201:6379
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~~~
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Sur les serveurs avec Redis (`172.19.3.200` et `172.19.3.201` dans notre exemple), il faut installer le paquet `xinetd` puis créer une configuration `/etc/xinetd.d/haproxy-agent-redis-role` :
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~~~
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service haproxy-agent-redis-role
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{
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socket_type = stream
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bind = 172.19.3.200
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port = 16379
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protocol = tcp
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wait = no
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type = UNLISTED
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user = root
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server = /usr/share/scripts/haproxy-agent-redis-role.sh
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log_on_failure += USERID
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disable = no
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only_from = 172.19.3.100
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}
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~~~
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On active ce service dans `/etc/services` :
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~~~
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haproxy-agent-redis-role 16379/tcp
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~~~
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Puis on redémarre `xinetd` : `systemctl restart xinetd`
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Enfin, on installe le script qui sert d'agent `/usr/share/scripts/haproxy-agent-redis-role.sh` :
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~~~.bash
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#!/bin/sh
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set -u
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config_var() {
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variable=$1
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file=$2
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test -f "${file}" && grep -E "^${variable}\s+.+$" "${file}" | awk '{ print $2 }' | sed -e "s/^[\"']//" -e "s/[\"']$//"
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}
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get_role() {
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host=$(config_var "bind" "${conf_file}")
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port=$(config_var "port" "${conf_file}")
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pass=$(config_var "requirepass" "${conf_file}")
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if [ -n "${pass}" ]; then
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export REDISCLI_AUTH="${pass}"
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fi
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cmd="${redis_cli_bin} -h ${host} -p ${port} INFO REPLICATION"
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${cmd} 2>/dev/null | grep -Eo "role:\w+" | cut -d ':' -f2
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}
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get_status() {
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systemctl is-active "${1}"
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}
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redis_cli_bin=$(command -v redis-cli)
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if [ -z "${redis_cli_bin}" ]; then
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printf "%s\n" "down # missing redis"
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exit 1
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fi
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if [ $# -lt 1 ]; then
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service="redis-server.service"
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conf_file="/etc/redis/redis.conf"
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else
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service="redis-server@${1}.service"
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conf_file="/etc/redis-${1}/redis.conf"
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fi
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if [ ! -r "${conf_file}" ]; then
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printf "%s\n" "down # missing config"
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exit 3
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fi
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status=$(get_status "${service}")
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case "${status}" in
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active)
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printf "%s " "up"
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;;
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inactive)
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printf "%s\n" "stopped # systemd:${status}"
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exit 1
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;;
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failed)
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printf "%s\n" "fail # systemd:${status}"
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exit 1
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;;
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*)
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printf "%s\n" "down # systemd:${status}"
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exit 1
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;;
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esac
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role=$(get_role "${conf_file}")
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case "${role}" in
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master)
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printf "%s" "ready # role:master"
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;;
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slave)
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printf "%s" "maint # role:slave"
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;;
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*)
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printf "%s" "maint # role:unknown"
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;;
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esac
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printf "\n"
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exit 0
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~~~
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### Redis multi-instances
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Ce script est compatible avec la présence de multiples instances de Redis.
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Si on l'exécute avec un argument `foo` il cherchera une configuration `/etc/redis-foo/redis.conf` et un service systemd `redis-server@foo`.
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Il faudra alors déclarer autant de services xinetd que d'instances à surveiller :
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~~~
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haproxy-agent-redis-role-foo 16380/tcp
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haproxy-agent-redis-role-bar 16381/tcp
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~~~
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Et enfin, modifier les services pour ajouter le paramètre `server_args` :
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~~~
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service haproxy-agent-redis-role-foo
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{
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socket_type = stream
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bind = 172.19.3.200
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port = 16380
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protocol = tcp
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wait = no
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type = UNLISTED
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user = root
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server = /usr/share/scripts/haproxy-agent-redis-role.sh
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server_args = foo
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log_on_failure += USERID
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disable = no
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only_from = 172.19.3.100
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}
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~~~
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## Benchmarks
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