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#!/bin/bash
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#
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# Script to make a proxy (ie HAProxy) capable of monitoring Galera cluster nodes properly
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#
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# Author: Olaf van Zandwijk <olaf.vanzandwijk@nedap.com>
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# Author: Raghavendra Prabhu <raghavendra.prabhu@percona.com>
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# Author: Ryan O'Hara <rohara@redhat.com>
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#
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# Documentation and download: https://github.com/olafz/percona-clustercheck
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#
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# Based on the original script from Unai Rodriguez
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#
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if [ -f @INSTALL_SYSCONFDIR@/sysconfig/clustercheck ]; then
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    . @INSTALL_SYSCONFDIR@/sysconfig/clustercheck
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fi
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MYSQL_USERNAME="${MYSQL_USERNAME-clustercheckuser}"
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MYSQL_PASSWORD="${MYSQL_PASSWORD-clustercheckpassword!}"
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MYSQL_HOST="${MYSQL_HOST:-127.0.0.1}"
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MYSQL_PORT="${MYSQL_PORT:-3306}"
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ERR_FILE="${ERR_FILE:-/dev/null}"
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AVAILABLE_WHEN_DONOR=${AVAILABLE_WHEN_DONOR:-0}
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AVAILABLE_WHEN_READONLY=${AVAILABLE_WHEN_READONLY:-1}
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DEFAULTS_EXTRA_FILE=${DEFAULTS_EXTRA_FILE:-@INSTALL_SYSCONFDIR@/my.cnf}
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#Timeout exists for instances where mysqld may be hung
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TIMEOUT=10
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if [[ -r $DEFAULTS_EXTRA_FILE ]];then
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    MYSQL_CMDLINE="mysql --defaults-extra-file=$DEFAULTS_EXTRA_FILE -nNE \
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                    --connect-timeout=$TIMEOUT \
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                    --user=${MYSQL_USERNAME} --password=${MYSQL_PASSWORD} \
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                    --host=${MYSQL_HOST} --port=${MYSQL_PORT}"
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else
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    MYSQL_CMDLINE="mysql -nNE --connect-timeout=$TIMEOUT \
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                    --user=${MYSQL_USERNAME} --password=${MYSQL_PASSWORD} \
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                    --host=${MYSQL_HOST} --port=${MYSQL_PORT}"
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fi
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#
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# Perform the query to check the wsrep_local_state
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#
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WSREP_STATUS=$($MYSQL_CMDLINE -e "SHOW STATUS LIKE 'wsrep_local_state';" \
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    2>${ERR_FILE} | tail -1 2>>${ERR_FILE})
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if [[ "${WSREP_STATUS}" == "4" ]] || [[ "${WSREP_STATUS}" == "2" && ${AVAILABLE_WHEN_DONOR} == 1 ]]
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then
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    # Check only when set to 0 to avoid latency in response.
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    if [[ $AVAILABLE_WHEN_READONLY -eq 0 ]];then
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        READ_ONLY=$($MYSQL_CMDLINE -e "SHOW GLOBAL VARIABLES LIKE 'read_only';" \
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                    2>${ERR_FILE} | tail -1 2>>${ERR_FILE})
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        if [[ "${READ_ONLY}" == "ON" ]];then
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            # Galera cluster node local state is 'Synced', but it is in
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            # read-only mode. The variable AVAILABLE_WHEN_READONLY is set to 0.
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            # => return HTTP 503
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            # Shell return-code is 1
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            echo -en "HTTP/1.1 503 Service Unavailable\r\n"
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            echo -en "Content-Type: text/plain\r\n"
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            echo -en "Connection: close\r\n"
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            echo -en "Content-Length: 35\r\n"
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            echo -en "\r\n"
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            echo -en "Galera cluster node is read-only.\r\n"
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            sleep 0.1
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            exit 1
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        fi
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    fi
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    # Galera cluster node local state is 'Synced' => return HTTP 200
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    # Shell return-code is 0
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    echo -en "HTTP/1.1 200 OK\r\n"
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    echo -en "Content-Type: text/plain\r\n"
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    echo -en "Connection: close\r\n"
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    echo -en "Content-Length: 32\r\n"
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    echo -en "\r\n"
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    echo -en "Galera cluster node is synced.\r\n"
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    sleep 0.1
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    exit 0
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else
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    # Galera cluster node local state is not 'Synced' => return HTTP 503
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    # Shell return-code is 1
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    echo -en "HTTP/1.1 503 Service Unavailable\r\n"
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    echo -en "Content-Type: text/plain\r\n"
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    echo -en "Connection: close\r\n"
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    echo -en "Content-Length: 36\r\n"
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    echo -en "\r\n"
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    echo -en "Galera cluster node is not synced.\r\n"
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    sleep 0.1
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    exit 1
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fi