#!/bin/sh
#
# Plugin for monitor JVM activity - GC Count -
#
# Usage:
#
#       Symlink into /etc/munin/plugins/ and add the monitored
#	alias name like :
#
#       ln -s /usr/share/munin/plugins/jstat__gccount \
#	  /etc/munin/plugins/jstat_<jvm alias>_gccount
#       This should, however, be given through autoconf and suggest.
#
# Requirements:
#
#	You need to execute your Java program under jsvc provided by
#	  http://jakarta.apache.org/commons/daemon/
#	which enables you to run your Java program with specified
#	pid file with -pidfile option.
#       A Brief setup documentation is also available at
#         http://tomcat.apache.org/tomcat-5.5-doc/setup.html
#
# Target:
#
#       Target Java Virtual Machine to monitor are:
#         Sun JDK 5.0 (http://java.sun.com/javase/)
#         Sun JDK 8.0 (http://java.sun.com/javase/)
#         BEA JRockit 5.0 (http://dev2dev.bea.com/jrockit/)
#
# Parameters:
#
#       config   (required)
#
# Config variables:
#
#       pidfilepath  - Which file path use. Defaults to '/var/run/jsvc.pid'
#       javahome     - override automatic detection of JRE directory
#       graphtitle   - Title of the graph (defaults to PID file location)
#

default_java_home=/usr/lib/jvm/default-java
[ -e "$default_java_home" ] || default_java_home=/usr/local/java/jdk

pidfilepath=${pidfilepath:-/var/run/jsvc.pid}
graphtitle=${graphtitle:-$pidfilepath}
JAVA_HOME=${javahome:-$default_java_home}

export JAVA_HOME


get_jdk_type() {
    local version
    if "${JAVA_HOME}/bin/java" -version 2>&1 | grep -qi 'jrockit'; then
        echo "bea"
    else
        version=$("${JAVA_HOME}/bin/java" -version 2>&1 | grep '^java version' | awk '{print $3}' | sed -e 's/\"//g' | cut -d'_' -f 1)
        if echo "$version" | grep -q '^1\.5\.'; then
            echo "sun15"
        else
            echo "sun"
        fi
  fi
}


print_config() {
    echo "graph_title GC Count $graphtitle"
    echo 'graph_args -l 0'
    echo 'graph_vlabel GC Count(times)'
    echo 'graph_total total'
    echo 'graph_info GC Count'
    echo 'graph_category virtualization'

    echo 'Young_GC.label Young_GC'
    echo 'Young_GC.min 0'
    if [ "${JDK_TYPE}" = "bea" ]; then
        echo 'Old_GC.label Old_GC'
        echo 'Old_GC.min 0'
    else
        echo 'Full_GC.label Full_GC'
        echo 'Full_GC.min 0'
    fi
}


print_stats() {
    local pid_num="$1"
    local awk_script
    if [ "${JDK_TYPE}" = "bea" ]; then
        # shellcheck disable=SC2016
        awk_script='{ YC = $4; OC = $5; print "Young_GC.value " YGC; print "Old_GC.value " FGC; }'
    elif [ "${JDK_TYPE}" = "sun15" ]; then
        # shellcheck disable=SC2016
        awk_script='{ YGC = $11; FGC = $13; print "Young_GC.value " YGC; print "Full_GC.value " FGC; }'
    else
        # example output of jstat for Java 1.8:
        #   S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT
        #   2048.0 2048.0 0.0 1344.0 694784.0 145013.5 1398272.0 414857.1 102400.0 96308.0 12544.0 11240.1 979 20.997 5 2.705 23.702
        # shellcheck disable=SC2016
        awk_script='{ YGC = $13; FGC = $15; print "Young_GC.value " YGC; print "Full_GC.value " FGC; }'
    fi
    "${JAVA_HOME}/bin/jstat" -gc "$pid_num" | tail -1 | awk "$awk_script"
}


#
# autoconf
#
if [ "$1" = "autoconf" ]; then

  if [ ! -x "${JAVA_HOME}/bin/jstat" ]; then
    echo "no (No jstat found in ${JAVA_HOME}/bin)"
  elif [ ! -f "$pidfilepath" ]; then
    echo "no (missing file $pidfilepath)"
  elif [ ! -r "$pidfilepath" ]; then
    echo "no (cannot read $pidfilepath)"
  else
    echo "yes"
  fi
  exit 0
fi


JDK_TYPE=$(get_jdk_type)


if [ "$1" = "config" ]; then
    print_config
    exit 0
fi

print_stats "$(cat "$pidfilepath")"
