Binary Talks

Update 1.1: nginx Check Plugin for Nagios

06.16.09 | 1 Comment

logo_nagiosLast week I’ve got an E-Mail by Jordi, who’s blogging at terraquis.net, with a few suggestions to the nginx check plugin I’ve recently released. He made two significant changes to the plugin:

  1. His version runs with bash only, but except bc all external calls have been replaced by bash built-ins
  2. There’s no temporary file anymore which has to be written to a temporary directory, nginx_status page output is saved into a variable

The plugin therefore runs much faster than my initial version of the plugin: 14-16ms plus the 1 second sleep interval between the two nginx_status checks.

And then I realized that writing output to a temporary file is just one thing: plain stupid. Why writing files when an information can be stored in a variable where it stays in memory?
Well, I can’t really say why I walked this way when I’ve written the first plugins, but I eventually had the right idea when I’ve written the Hadoop DFS check. There I already store the information within variables. The only guess why I did this is that I’ve assumed that storing longer output in variables just would be too much.

But anyway, there has to be room for improvements, right? Therefore, expect a few reworks within the next days, …

The script

Below is the revised script I’ve already uploaded yesterday to Nagios and MonitoringExchange. It runs much faster than the initial version and doesn’t write files anymore. You may also stick to the output below or do the SVN way.

user@host: ~ $ svn co svn://svn.matejunkie.com/nagios-plugins/stable/check_nginx/ check_nginx/
#!/bin/sh
 
#   This program is free software; you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 2 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
PROGNAME=`basename $0`
VERSION="Version 1.1,"
AUTHOR="2009, Mike Adolphs (http://www.matejunkie.com/)"
 
ST_OK=0
ST_WR=1
ST_CR=2
ST_UK=3
hostname="localhost"
port=80
path_pid=/var/run
name_pid="nginx.pid"
status_page="nginx_status"
pid_check=1
secure=0
 
print_version() {
    echo "$VERSION $AUTHOR"
}
 
print_help() {
    print_version $PROGNAME $VERSION
    echo ""
    echo "$PROGNAME is a Nagios plugin to check whether nginx is running."
    echo "It also parses the nginx's status page to get requests and"
    echo "connections per second as well as requests per connection. You"
    echo "may have to alter your nginx configuration so that the plugin"
    echo "can access the server's status page."
    echo "The plugin is highly configurable for this reason. See below for"
    echo "available options."
    echo ""
    echo "$PROGNAME -H localhost -P 80 -p /var/run -n nginx.pid "
	echo "  -s nginx_statut -o /tmp [-w INT] [-c INT] [-S] [-N]"
    echo ""
    echo "Options:"
    echo "  -H/--hostname)"
    echo "     Defines the hostname. Default is: localhost"
    echo "  -P/--port)"
    echo "     Defines the port. Default is: 80"
    echo "  -p/--path-pid)"
    echo "     Path where nginx's pid file is being stored. You might need"
    echo "     to alter this path according to your distribution. Default"
    echo "     is: /var/run"
    echo "  -n/--name_pid)"
    echo "     Name of the pid file. Default is: nginx.pid"
    echo "  -N/--no-pid-check)"
    echo "     Turn this on, if you don't want to check for a pid file"
    echo "     whether nginx is running, e.g. when you're checking a"
    echo "     remote server. Default is: off"
    echo "  -s/--status-page)"
    echo "     Name of the server's status page defined in the location"
    echo "     directive of your nginx configuration. Default is:"
    echo "     nginx_status"
    echo "  -S/--secure)"
    echo "     In case your server is only reachable via SSL, use this"
    echo "     this switch to use HTTPS instead of HTTP. Default is: off"
    echo "  -w/--warning)"
    echo "     Sets a warning level for requests per second. Default is: off"
    echo "  -c/--critical)"
    echo "     Sets a critical level for requests per second. Default is:"
	echo "     off"
    exit $ST_UK
}
 
while test -n "$1"; do
    case "$1" in
        -help|-h)
            print_help
            exit $ST_UK
            ;;
        --version|-v)
            print_version $PROGNAME $VERSION
            exit $ST_UK
            ;;
        --hostname|-H)
            hostname=$2
            shift
            ;;
        --port|-P)
            port=$2
            shift
            ;;
        --path-pid|-p)
            path_pid=$2
            shift
            ;;
        --name-pid|-n)
            name_pid=$2
            shift
            ;;
        --no-pid-check|-N)
            pid_check=0
            ;;
        --status-page|-s)
            status_page=$2
            shift
            ;;
        --secure|-S)
            secure=1
            ;;
        --warning|-w)
            warning=$2
            shift
            ;;
        --critical|-c)
            critical=$2
            shift
            ;;
        *)
            echo "Unknown argument: $1"
            print_help
            exit $ST_UK
            ;;
        esac
    shift
done
 
get_wcdiff() {
    if [ ! -z "$warning" -a ! -z "$critical" ]
    then
        wclvls=1
 
        if [ ${warning} -ge ${critical} ]
        then
            wcdiff=1
        fi
    elif [ ! -z "$warning" -a -z "$critical" ]
    then
        wcdiff=2
    elif [ -z "$warning" -a ! -z "$critical" ]
    then
        wcdiff=3
    fi
}
 
val_wcdiff() {
    if [ "$wcdiff" = 1 ]
    then
        echo "Please adjust your warning/critical thresholds. The warning \
must be lower than the critical level!"
        exit $ST_UK
    elif [ "$wcdiff" = 2 ]
    then
        echo "Please also set a critical value when you want to use \
warning/critical thresholds!"
        exit $ST_UK
    elif [ "$wcdiff" = 3 ]
    then
        echo "Please also set a warning value when you want to use \
warning/critical thresholds!"
        exit $ST_UK
    fi
}
 
check_pid() {
    if [ -f "$path_pid/$name_pid" ]
    then
        retval=0
    else
        retval=1
    fi
}
 
get_status() {
    if [ "$secure" = 1 ]
    then
        wget_opts="-O- -q -t 3 -T 3 --no-check-certificate"
        out1=`wget ${wget_opts} http://${hostname}:${port}/${status_page}`
        sleep 1
        out2=`wget ${wget_opts} http://${hostname}:${port}/${status_page}`
    else        
        wget_opts="-O- -q -t 3 -T 3"
        out1=`wget ${wget_opts} http://${hostname}:${port}/${status_page}`
        sleep 1
        out2=`wget ${wget_opts} http://${hostname}:${port}/${status_page}`
    fi
 
    if [ -z "$out1" -o -z "$out2" ]
    then
        echo "UNKNOWN - Local copy/copies of $status_page is empty."
        exit $ST_UK
    fi
}
 
get_vals() {
    tmp1_reqpsec=`echo ${out1}|awk '{print $10}'`
    tmp2_reqpsec=`echo ${out2}|awk '{print $10}'`
    reqpsec=`expr $tmp2_reqpsec - $tmp1_reqpsec`
 
    tmp1_conpsec=`echo ${out1}|awk '{print $9}'`
    tmp2_conpsec=`echo ${out2}|awk '{print $9}'`
    conpsec=`expr $tmp2_conpsec - $tmp1_conpsec`
 
    reqpcon=`echo "scale=2; $reqpsec / $conpsec" | bc -l`
    if [ "$reqpcon" = ".99" ]
    then
        reqpcon="1.00"
    fi
}
 
do_output() {
    output="nginx is running. $reqpsec requests per second, $conpsec \
connections per second ($reqpcon requests per connection)"
}
 
do_perfdata() {
    perfdata="'reqpsec'=$reqpsec 'conpsec'=$conpsec 'conpreq'=$reqpcon"
}
 
# Here we go!
get_wcdiff
val_wcdiff
 
if [ ${pid_check} = 1 ]
then
    check_pid
    if [ "$retval" = 1 ]
    then
        echo "There's no pid file for nginx. Is nginx running? Please \
also make sure whether your pid path and name is correct."
        exit $ST_CR
    fi
fi
 
get_status
get_vals
do_output
do_perfdata
 
if [ -n "$warning" -a -n "$critical" ]
then
    if [ "$reqpsec" -ge "$warning" -a "$reqpsec" -lt "$critical" ]
    then
        echo "WARNING - ${output} | ${perfdata}"
	exit $ST_WR
    elif [ "$reqpsec" -ge "$critical" ]
    then
        echo "CRITICAL - ${output} | ${perfdata}"
	exit $ST_CR
    else
        echo "OK - ${output} | ${perfdata} ]"
	exit $ST_OK
    fi
else
    echo "OK - ${output} | ${perfdata}"
    exit $ST_OK
fi

Jordi’s script

This is Jordi’s bash built-in (plus bc) version which runs even faster. Feel free to copy the output below.

#!/bin/bash
 
#   This program is free software; you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 2 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
PROGNAME=`basename $0`
VERSION="Version 1.0,"
AUTHOR="2009, Mike Adolphs (http://www.matejunkie.com/)"
 
ST_OK=0
ST_WR=1
ST_CR=2
ST_UK=3
hostname="localhost"
port=80
path_pid=/var/run
name_pid="nginx.pid"
status_page="nginx_status"
pid_check=1
secure=0
 
print_version() {
    echo "$VERSION $AUTHOR"
}
 
print_help() {
    print_version $PROGNAME $VERSION
    echo ""
    echo "$PROGNAME is a Nagios plugin to check whether nginx is running."
    echo "It also parses the nginx's status page to get requests and"
    echo "connections per second as well as requests per connection. You"
    echo "may have to alter your nginx configuration so that the plugin"
    echo "can access the server's status page."
    echo "The plugin is highly configurable for this reason. See below for"
    echo "available options."
    echo ""
    echo "$PROGNAME -H localhost -P 80 -p /var/run -n nginx.pid "
	echo "  -s nginx_statut -o /tmp [-w INT] [-c INT] [-S] [-N]"
    echo ""
    echo "Options:"
    echo "  -H/--hostname)"
    echo "     Defines the hostname. Default is: localhost"
    echo "  -P/--port)"
    echo "     Defines the port. Default is: 80"
    echo "  -p/--path-pid)"
    echo "     Path where nginx's pid file is being stored. You might need"
    echo "     to alter this path according to your distribution. Default"
    echo "     is: /var/run"
    echo "  -n/--name_pid)"
    echo "     Name of the pid file. Default is: nginx.pid"
    echo "  -N/--no-pid-check)"
    echo "     Turn this on, if you don't want to check for a pid file"
    echo "     whether nginx is running, e.g. when you're checking a"
    echo "     remote server. Default is: off"
    echo "  -s/--status-page)"
    echo "     Name of the server's status page defined in the location"
    echo "     directive of your nginx configuration. Default is:"
    echo "     nginx_status"
    echo "  -o/--output-directory)"
    echo "     Unneeded. The option is preserved for backwards compatibility."
    echo "  -S/--secure)"
    echo "     In case your server is only reachable via SSL, use this"
    echo "     this switch to use HTTPS instead of HTTP. Default is: off"
    echo "  -w/--warning)"
    echo "     Sets a warning level for requests per second. Default is: off"
    echo "  -c/--critical)"
    echo "     Sets a critical level for requests per second. Default is:"
	echo "     off"
    exit $ST_UK
}
 
while test -n "$1"; do
    case "$1" in
        -help|-h)
            print_help
            exit $ST_UK
            ;;
        --version|-v)
            print_version $PROGNAME $VERSION
            exit $ST_UK
            ;;
        --hostname|-H)
            hostname=$2
            shift
            ;;
        --port|-P)
            port=$2
            shift
            ;;
        --path-pid|-p)
            path_pid=$2
            shift
            ;;
        --name-pid|-n)
            name_pid=$2
            shift
            ;;
        --no-pid-check|-N)
            pid_check=0
            ;;
        --status-page|-s)
            status_page=$2
            shift
            ;;
        --output-directory|-o)
            output_dir=$2
            shift
            ;;
        --secure|-S)
            secure=1
            ;;
        --warning|-w)
            warning=$2
            shift
            ;;
        --critical|-c)
            critical=$2
            shift
            ;;
        *)
            echo "Unknown argument: $1"
            print_help
            exit $ST_UK
            ;;
        esac
    shift
done
 
get_wcdiff() {
    if [ ! -z "$warning" -a ! -z "$critical" ]
    then
        wclvls=1
 
        if [ ${warning} -gt ${critical} ]
        then
            wcdiff=1
        fi
    elif [ ! -z "$warning" -a -z "$critical" ]
    then
        wcdiff=2
    elif [ -z "$warning" -a ! -z "$critical" ]
    then
        wcdiff=3
    fi
}
 
val_wcdiff() {
    if [ "$wcdiff" = 1 ]
    then
        echo "Please adjust your warning/critical thresholds. The warning \
must be lower than the critical level!"
        exit $ST_UK
    elif [ "$wcdiff" = 2 ]
    then
        echo "Please also set a critical value when you want to use \
warning/critical thresholds!"
        exit $ST_UK
    elif [ "$wcdiff" = 3 ]
    then
        echo "Please also set a warning value when you want to use \
warning/critical thresholds!"
        exit $ST_UK
    fi
}
 
check_pid() {
    if [ -f "$path_pid/$name_pid" ]
    then
        retval=0
    else
        retval=1
    fi
}
 
get_status() {
    url="http://${hostname}:${port}/${status_page}"
 
    if [ "$secure" = 1 ] ; then
        wget_opts="-O- -q -t 3 -t 3 --no-check-certificate"
    else
        wget_opts="-O- -q -t 3 -t 3"
    fi
 
    out1=$(wget ${wget_opts} ${url})
    sleep 1
    out2=$(wget ${wget_opts} ${url})
 
    # Both commands must return some content.
    if [ -z "${out1}" -o -z "${out2}" ] ; then
        echo "UNKNOWN - Local copy/copies of $status_page is empty."
        exit $ST_UK
    fi
}
 
get_vals() {
    # Convert into an array.
    values1=(${out1})
    values2=(${out2})
 
    reqpsec=$(( ${values2[9]} - ${values1[9]} ))
    conpsec=$(( ${values2[8]} - ${values1[8]} ))
 
    reqpcon=`echo "scale=2; $reqpsec / $conpsec" | bc -l`
    if [ "$reqpcon" = ".99" ]
    then
        reqpcon="1.00"
    fi
}
 
do_output() {
    output="nginx is running. $reqpsec requests per second, $conpsec \
connections per second ($reqpcon requests per connection)"
}
 
do_perfdata() {
    perfdata="'reqpsec'=$reqpsec 'conpsec'=$conpsec 'conpreq'=$reqpcon"
}
 
# Here we go!
get_wcdiff
val_wcdiff
 
if [ ${pid_check} = 1 ]
then
    check_pid
    if [ "$retval" = 1 ]
    then
        echo "There's no pid file for nginx. Is nginx running? Please \
also make sure whether your pid path and name is correct."
        exit $ST_CR
    fi
fi
 
get_status
get_vals
do_output
do_perfdata
 
if [ -n "$warning" -a -n "$critical" ]
then
    if [ "$reqpsec" -ge "$warning" -a "$reqpsec" -lt "$critical" ]
    then
        echo "WARNING - ${output} | ${perfdata}"
	exit $ST_WR
    elif [ "$reqpsec" -ge "$critical" ]
    then
        echo "CRITICAL - ${output} | ${perfdata}"
	exit $ST_CR
    else
        echo "OK - ${output} | ${perfdata} ]"
	exit $ST_OK
    fi
else
    echo "OK - ${output} | ${perfdata}"
    exit $ST_OK
fi

License

As always this little script is ment to be sh-compliant and released under the terms of the GPL Version 2 only. Feel free to subscribe via rss to get updates on this one. More options will be added in the future.

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