varnishsync

#!/bin/bash
# Author: Björn Andersson <bjorn.andersson@piratpartiet.se>
#
# Piratpartiet has two servers running Varnish and keeping them both in sync
# started to get cumbersome. A quick search on Google gave nothing so I wrote
# this script to ease the maintenance of activating new configuration files on
# a Varnish farm.
#
# How the script works:
# - The directory holding the varnish configuration will be synced to all
#   hosts in $HOSTS using ssh as carrier
# - The currently active configuration on all hosts get cached
#   In case something goes awry this configuration will get activated again
# - All hosts will get the new configuration loaded.
#   If you pass an argument that name will be used + the current date and time
# - The configuration will be activated on all hosts, if an error occurs all
#   hosts that managed to get the new configuration activated will get their
#   configurations reverted to the old configuration.
#

HOSTS=(morgan rackham)
VARNISH_PATH=/etc/varnish/
VARNISH_VCL=/etc/varnish/vcl.conf
ADMIN_PORT=6082
RSYNC_PARAMS=-a
RSYNC_USER=varnishsync
VARNISHADM_PARAMS=''

###################
# Don't edit below

source /etc/default/varnish

CONF_NAME=''
if [ "${1}" = "" ] ; then
    CONF_NAME=`date "+reload-%Y%m%d-%H%M.%S"`
else
    CONF_NAME=`date "+${1}-%Y%m%d-%H%M.%S"`
fi

function copy_configuration_to
{
    HOST=$1
    `rsync $RSYNC_PARAMS $VARNISH_PATH $RSYNC_USER@$HOST:$VARNISH_PATH`
}

function load_configuration_on
{
    HOST=$1
    CONFIG_NAME=$2
    eval ssh $RSYNC_USER@$HOST "varnishadm -T localhost:$ADMIN_PORT $VARNISHADM_PARAMS vcl.load $CONFIG_NAME $VARNISH_VCL > /dev/null"
}

function use_configuration_on
{
    HOST=$1
    CONFIG_NAME=$2
    eval ssh $RSYNC_USER@$HOST "varnishadm -T localhost:$ADMIN_PORT $VARNISHADM_PARAMS vcl.use $CONFIG_NAME"
}

function old_configuration_name_on
{
    HOST=$1
    eval ssh $RSYNC_USER@$HOST "varnishadm -T localhost:$ADMIN_PORT $VARNISHADM_PARAMS vcl.list | awk '/active/ {print \$3}'"
}

function did_an_error_occur
{
    return_code=$1
    exit_code=$2
    message_on_error=$3
    if [ "${return_code}" != "0" ] ; then
        echo $message_on_error
        exit $exit_code
    fi
}

PREVIOUS_CONFIG=()

i=0
while [ "$i" -lt "${#HOSTS[@]}" ] ; do
    HOST=${HOSTS[$i]}

    i=`expr $i + 1`
    if [ $HOST = $INSTANCE ] ; then continue ; fi

    copy_configuration_to $HOST
    did_an_error_occur $? 1 "Error copying configuration to host ${HOST}!"
done

i=0
while [ "$i" -lt "${#HOSTS[@]}" ] ; do
    conf=$(old_configuration_name_on ${HOSTS[${i}]})
    did_an_error_occur $? 2 "An error occured trying to get the previous configuration name!"

    PREVIOUS_CONFIG[$i]=$conf
    i=`expr $i + 1`
done

# Time to start loading the configurations
i=0
while [ "$i" -lt "${#HOSTS[@]}" ] ; do
    HOST=${HOSTS[$i]}
    load_configuration_on $HOST $CONF_NAME
    did_an_error_occur $? 3 "Something went badly when trying to load the new configuration!"

    i=`expr $i + 1`
done

# Now all hosts should've loaded the new conf without problems so try and activate it.
# If something goes wrong with the activation revisit the previously done
# hosts, if any, and load their previous config instead
i=0
while [ "$i" -lt "${#HOSTS[@]}" ] ; do
    HOST=${HOSTS[$i]}
    use_configuration_on $HOST $CONF_NAME

    if [ "$?" != "0" ] ; then
        echo "An error occured trying to activate the new configuration on ${HOST}!"

        if [ "$i" -ne "0" ] ; then
            echo "Will try to re-active the old configuration on the hosts that succeeded"

            j=0
            while [ "$j" -lt "$i" ] ; do
                old_host=${HOSTS[$j]}
                prev_conf=${PREVIOUS_CONFIG[$j]}
                use_configuration_on $old_host $prev_conf
                if [ "$?" -eq "0" ] ; then
                    echo "${old_host} reverted to ${prev_conf}"
                else
                    echo "An error occured trying to revert ${old_host} to ${prev_conf}"
                    exit 5

                fi

                j=`expr $j + 1`
            done

            exit 4
        fi
    fi

    i=`expr $i + 1`
done