#!/bin/sh
#
# Plugin for monitor JVM activity - Heap Usage -
#
# Usage:
#
#       Symlink into /etc/munin/plugins/ and add the monitored
#	alias name like :
#
#       ln -s /usr/share/munin/plugins/jstat__heap \
#	  /etc/munin/plugins/jstat_<jvm alias>_heap
#       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/)
#         OpenJDK 1.7 .. 11 (https://openjdk.java.net/)
#         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
        echo "sun"
  fi
}


print_config() {
    echo "graph_title Heap Usage $graphtitle"
    echo "graph_args --base 1024 -l 0"
    echo "graph_vlabel Heap Usage(Bytes)"
    echo "graph_info Heap Usage"
    echo "graph_category virtualization"

    if [ "${JDK_TYPE}" = "bea" ]; then
        echo "NurserySize.label NurserySize"
        echo "HeapSize.label HeapSize"
        echo "UsedHeapSize.label UsedHeapSize"
        echo "NurserySize.draw AREA"
        echo "HeapSize.draw STACK"
        echo "UsedHeapSize.draw STACK"
    else
        echo "Eden_Used.label Eden_Used"
        echo "Eden_Free.label Eden_Free"
        echo "Survivor0_Used.label Survivor0_Used"
        echo "Survivor0_Free.label Survivor0_Free"
        echo "Survivor1_Used.label Survivor1_Used"
        echo "Survivor1_Free.label Survivor1_Free"
        echo "Old_Used.label Old_Used"
        echo "Old_Free.label Old_Free"
        echo "Permanent_Used.label Permanent_Used"
        echo "Permanent_Free.label Permanent_Free"
        echo "Eden_Used.draw AREA"
        echo "Eden_Free.draw STACK"
        echo "Survivor0_Used.draw STACK"
        echo "Survivor0_Free.draw STACK"
        echo "Survivor1_Used.draw STACK"
        echo "Survivor1_Free.draw STACK"
        echo "Old_Used.draw STACK"
        echo "Old_Free.draw STACK"
        echo "Permanent_Used.draw STACK"
        echo "Permanent_Free.draw STACK"
    fi
}


print_stats() {
    local pid_num="$1"
    local awk_script
    if [ "${JDK_TYPE}" = "bea" ]; then
        # shellcheck disable=SC2016
        awk_script='{
            HeapSize = $1;
            NurserySize = $2;
            UsedHeapSize = $3;
            print "NurserySize.value " NurserySize * 1024;
            print "HeapSize.value " HeapSize * 1024;
            print "UsedHeapSize.value " UsedHeapSize * 1024; }'
    else
        # List & Order of columns of jstat changes with java versions
        # idx["YGC"] is index of YGC column in output (i.e. 13)
        # $idx["YGC"] then accesses the value at this position (taken from 2nd line of the output)
        # shellcheck disable=SC2016
        awk_script='
	    NR==1 { 
                for (i=1;i<=NF;i++) idx[$i]=i
            }
            NR==2 {
                S0F = $idx["S0C"] - $idx["S0U"];
                S1F = $idx["S1C"] - $idx["S1U"];
                EF  = $idx["EC"]  - $idx["EU"];
                OF  = $idx["OC"]  - $idx["OU"];
                # Java <8 has Permanent Generation (PU,PC columns), while >=8 has/names it Metaspace (MU,MC)
                if (idx["MU"] == "") {
                    idx["MU"] = idx["PU"];
                    idx["MC"] = idx["PC"];
                }
                MF  = $idx["MC"]  - $idx["MU"];
                print "Eden_Used.value " $idx["EU"] * 1024;
                print "Eden_Free.value " EF * 1024;
                print "Survivor0_Used.value " $idx["S0U"] * 1024;
                print "Survivor0_Free.value " S0F * 1024;
                print "Survivor1_Used.value " $idx["S1U"] * 1024;
                print "Survivor1_Free.value " S1F * 1024;
                print "Old_Used.value " $idx["OU"] * 1024;
                print "Old_Free.value " OF * 1024;
                print "Permanent_Used.value " $idx["MU"] * 1024;
                print "Permanent_Free.value " MF * 1024;
            }'
    fi
    "${JAVA_HOME}/bin/jstat" -gc "$pid_num" | awk "$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
fi

print_stats "$(cat "$pidfilepath")"