#!/bin/bash

#

# Script to make a proxy (ie HAProxy) capable of monitoring Galera cluster nodes properly

#

# Author: Olaf van Zandwijk <olaf.vanzandwijk@nedap.com>

# Author: Raghavendra Prabhu <raghavendra.prabhu@percona.com>

# Author: Ryan O'Hara <rohara@redhat.com>

#

# Documentation and download: https://github.com/olafz/percona-clustercheck

#

# Based on the original script from Unai Rodriguez

#

if [ -f @INSTALL_SYSCONFDIR@/sysconfig/clustercheck ]; then

    . @INSTALL_SYSCONFDIR@/sysconfig/clustercheck

fi

MYSQL_USERNAME="${MYSQL_USERNAME-clustercheckuser}"

MYSQL_PASSWORD="${MYSQL_PASSWORD-clustercheckpassword!}"

MYSQL_HOST="${MYSQL_HOST:-127.0.0.1}"

MYSQL_PORT="${MYSQL_PORT:-3306}"

ERR_FILE="${ERR_FILE:-/dev/null}"

AVAILABLE_WHEN_DONOR=${AVAILABLE_WHEN_DONOR:-0}

AVAILABLE_WHEN_READONLY=${AVAILABLE_WHEN_READONLY:-1}

DEFAULTS_EXTRA_FILE=${DEFAULTS_EXTRA_FILE:-@INSTALL_SYSCONFDIR@/my.cnf}

#Timeout exists for instances where mysqld may be hung

TIMEOUT=10

if [[ -r $DEFAULTS_EXTRA_FILE ]];then

    MYSQL_CMDLINE="mysql --defaults-extra-file=$DEFAULTS_EXTRA_FILE -nNE \

                    --connect-timeout=$TIMEOUT \

                    --user=${MYSQL_USERNAME} --password=${MYSQL_PASSWORD} \

                    --host=${MYSQL_HOST} --port=${MYSQL_PORT}"

else

    MYSQL_CMDLINE="mysql -nNE --connect-timeout=$TIMEOUT \

                    --user=${MYSQL_USERNAME} --password=${MYSQL_PASSWORD} \

                    --host=${MYSQL_HOST} --port=${MYSQL_PORT}"

fi

#

# Perform the query to check the wsrep_local_state

#

WSREP_STATUS=$($MYSQL_CMDLINE -e "SHOW STATUS LIKE 'wsrep_local_state';" \

    2>${ERR_FILE} | tail -1 2>>${ERR_FILE})

if [[ "${WSREP_STATUS}" == "4" ]] || [[ "${WSREP_STATUS}" == "2" && ${AVAILABLE_WHEN_DONOR} == 1 ]]

then

    # Check only when set to 0 to avoid latency in response.

    if [[ $AVAILABLE_WHEN_READONLY -eq 0 ]];then

        READ_ONLY=$($MYSQL_CMDLINE -e "SHOW GLOBAL VARIABLES LIKE 'read_only';" \

                    2>${ERR_FILE} | tail -1 2>>${ERR_FILE})

        if [[ "${READ_ONLY}" == "ON" ]];then

            # Galera cluster node local state is 'Synced', but it is in

            # read-only mode. The variable AVAILABLE_WHEN_READONLY is set to 0.

            # => return HTTP 503

            # Shell return-code is 1

            echo -en "HTTP/1.1 503 Service Unavailable\r\n"

            echo -en "Content-Type: text/plain\r\n"

            echo -en "Connection: close\r\n"

            echo -en "Content-Length: 35\r\n"

            echo -en "\r\n"

            echo -en "Galera cluster node is read-only.\r\n"

            sleep 0.1

            exit 1

        fi

    fi

    # Galera cluster node local state is 'Synced' => return HTTP 200

    # Shell return-code is 0

    echo -en "HTTP/1.1 200 OK\r\n"

    echo -en "Content-Type: text/plain\r\n"

    echo -en "Connection: close\r\n"

    echo -en "Content-Length: 32\r\n"

    echo -en "\r\n"

    echo -en "Galera cluster node is synced.\r\n"

    sleep 0.1

    exit 0

else

    # Galera cluster node local state is not 'Synced' => return HTTP 503

    # Shell return-code is 1

    echo -en "HTTP/1.1 503 Service Unavailable\r\n"

    echo -en "Content-Type: text/plain\r\n"

    echo -en "Connection: close\r\n"

    echo -en "Content-Length: 36\r\n"

    echo -en "\r\n"

    echo -en "Galera cluster node is not synced.\r\n"

    sleep 0.1

    exit 1

fi