Jmap can't connect to make a dump

Question

We have an open beta of an app which occasionally causes the heapspace to overflow. The JVM reacts by going on a permanent vacation.

To analyze this I would like to

Answer 1

In my case it is not as simple as check the user :(

I have a script called collectd-java which invokes jstat and jmap. I've checked by top that such script is launched, as expected, by the user owning the JVM. However, jstat gives me what I need and jmap can't attach. Here is the script - the echo stuff is just the format I need to present the values:

HOSTNAME="${COLLECTD_HOSTNAME:-localhost}"
INTERVAL="${COLLECTD_INTERVAL:-60}"
MAIN_CLASS="my.fully.qualified.MainClass"
PID=$(pgrep -f ${MAIN_CLASS})

get_jstat_classloaderdata() {
VALUE=`jstat -class $PID 1 1 | awk '{print $1}' | grep -vi loaded`
echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-java_classloader_loaded\" interval=$INTERVAL N:$VALUE"

VALUE=`jstat -class $PID 1 1 | awk '{print $2}' | grep -vi bytes`
echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-java_classloader_bytesload\" interval=$INTERVAL N:$VALUE"

VALUE=`jstat -class $PID 1 1 | awk '{print $3}' | grep -vi unload`
echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-java_classloader_unloaded\" interval=$INTERVAL N:$VALUE"

VALUE=`jstat -class $PID 1 1 | awk '{print $4}' | grep -vi bytes`
echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-java_classloader_bytesunload\" interval=$INTERVAL N:$VALUE"

VALUE=`jstat -class $PID 1 1 | awk '{print $5}' | grep -vi time`
echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-java_classloader_time\" interval=$INTERVAL N:$VALUE"
}

get_jmap_heapdata() {
        VALUE=$(jmap -heap ${PID} | grep MinHeapFreeRatio |awk '{print $3}')
        echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-jmap_minheapfreeratio\" interval=$INTERVAL N:$VALUE"

        VALUE=$(jmap -heap ${PID} | grep   MaxHeapFreeRatio|awk '{print $3}')
        echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-jmap_maxheapfreeratio\" interval=$INTERVAL N:$VALUE"

        VALUE=$(jmap -heap ${PID} | grep   MaxHeapSize|awk '{print $3}')
        echo "PUTVAL \"$HOSTNAME/exec-cecoco/gauge-jmap_maxheapsize\" interval=$INTERVAL N:$VALUE"
}
##Do it
get_jmap_heapdata
get_jstat_classloaderdata

Jstat succeeds and jmap fails. Does anyone understands it ?