#!/bin/bash
#
# Script to make a proxy (ie HAProxy) capable of monitoring Percona XtraDB Cluster nodes properly
#
# Author: Olaf van Zandwijk <olaf.vanzandwijk@nedap.com>
# Author: Raghavendra Prabhu <raghavendra.prabhu@percona.com>
#
# Documentation and download: https://github.com/olafz/percona-clustercheck
#
# Based on the original script from Unai Rodriguez
#
# This implementation depends on the presence of a ~/.my.cnf file for the mysql username and password.

if [[ $1 == '-h' || $1 == '--help' ]]; then
    echo "Usage: $0 <available_when_donor=0|1> <available_when_readonly=0|1> <log_file> <defaults_extra_file>"
    exit 1
fi

# if the disabled file is present, return 503. This allows
# admins to manually remove a node from a cluster easily.
if [ -e "/var/tmp/clustercheck.disabled" ]; then
    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: 51\r\n"
    echo -en "\r\n"
    echo -en "Percona XtraDB Cluster Node is manually disabled.\r\n"
    sleep 0.1
    exit 1
fi

AVAILABLE_WHEN_DONOR=${1:-1}
AVAILABLE_WHEN_READONLY=${2:-1}
ERR_FILE="${3:-/dev/null}"
DEFAULTS_EXTRA_FILE="${4:-/root/.my.cnf}"

#Timeout exists for instances where mysqld may be hung
TIMEOUT=10

EXTRA_ARGS=""
if [[ -r $DEFAULTS_EXTRA_FILE ]]; then
    MYSQL_CMDLINE="mysql --defaults-extra-file=$DEFAULTS_EXTRA_FILE --connect-timeout=$TIMEOUT ${EXTRA_ARGS}"
else
    MYSQL_CMDLINE="mysql --connect-timeout=$TIMEOUT ${EXTRA_ARGS}"
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 | awk '{print $2;}' 2>>${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 | awk '{print $2;}' 2>>${ERR_FILE})
        if [[ "${READ_ONLY}" == "ON" ]]; then
            # Percona XtraDB Cluster node local state is 'Synced', but it is in
            # read-only mode. The variable AVAILABLE_WHEN_READONLY is set to 0.
            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: 43\r\n"
            echo -en "\r\n"
            echo -en "Percona XtraDB Cluster Node is read-only.\r\n"
            sleep 0.1
            exit 1
        fi
     fi
    # Percona XtraDB Cluster node local state is 'Synced'
    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: 40\r\n"
    echo -en "\r\n"
    echo -en "Percona XtraDB Cluster Node is synced.\r\n"
    sleep 0.1
    exit 0
else
    # Percona XtraDB Cluster node local state is not 'Synced'
    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: 44\r\n"
    echo -en "\r\n"
    echo -en "Percona XtraDB Cluster Node is not synced.\r\n"
    sleep 0.1
    exit 1
fi