💩 The dumper 💩 Dump heap and thread dumps on an JVM-running app using Kubectl

kubernetes-jvm-dump-tool.sh

#!/usr/bin/env bash

# Usage: pod-dump <namespace> <pod-identifier>
# Summary: Grab a heap- and thread-dump of an app running on an active k8s pod ✨

if [ -z "$*" ]; then
    echo -e "
    Welcome to 💩 the Dumper 💩! 👋
    This will trigger a dump of heap and thread for a specific pod on a defined namespace. Is it safe?! Yes, this is fairly safe to run! Worst case?: Stop-the-world.
    @usage:
      pod-dump <namespace> <pod>
    @params:
      namespace: represents the k8s namespace
      pod: represents a deployed pod within the namespace
    @produces:
      dump : ./dumps/<the-dump>.{heap|thread}
    @examples:
      pod-dump my-awzm-namespace whatever-pod-name-1234abcdef
    @q/a:
      How to get the namespace?
        k get namespaces
      How to get the pods for a namespace?
        k get pods -n <namespace>
      What happens if I define wrong pod?
        The script runs, and you'll get an error in there somewhere. Read the error.
    ";
    exit 1
fi

if [ ! "$(command -v kubectl)" ]; then
  echo "💩⛔️ Oh no! No kubectl found! Install this tool first using e.g brew install kubectl"
  exit 1
fi

echo -e "
  Howdy 👋
  Welcome to 💩 the Dumper 💩
  Sit back, relax and await a proper dump which will pop on to your computer in a flash(ish)!"

namespace=${1}
podIdentifier=${2}
jvmPid=1
defaultDumpFolder=dumps
defaultDumpPath=./${defaultDumpFolder}
defaultHeapDumpName="dump-$(echo "${podIdentifier}" | cut -d "-" -f1)-$(date +"%Y-%m-%d_%H-%M").heap"
defaultHeapDumpPath="app/${defaultHeapDumpName}"
defaultHeapFile="${defaultDumpPath}"/${defaultHeapDumpName}
defaultThreadDumpName="dump-$(echo "${podIdentifier}" | cut -d "-" -f1)-$(date +"%Y-%m-%d_%H-%M").thread"
defaultThreadDumpPath="app/${defaultThreadDumpName}"
defaultThreadFile="${defaultDumpPath}"/${defaultThreadDumpName}

if [ -z "${namespace}" ]; then
  echo "💩⛔️ The Dumper isn't prepared with namespace. See the usage for more details"
  exit 1
fi
if [ -z "${podIdentifier}" ]; then
  echo "💩⛔ The Dumper isn't prepared with pod. See the usage for more details"
  exit 1
fi

echo -e "
  @params:
    namespace        : ${namespace}
    pod              : ${podIdentifier}
    heap dump path   : ${defaultHeapFile}
    thread dump path : ${defaultThreadFile}
"

if [ ! -d "${defaultDumpPath}" ]; then
  echo "💩️ Folder required for the Dumper not found. Creating ${defaultDumpPath}"
  mkdir "${defaultDumpFolder}"
fi

echo "⏱  (1/6) Creating heap dump on the pod ${podIdentifier}"
if [[ ! $(kubectl exec -n "${namespace}" "${podIdentifier}" -- jmap -dump:live,format=b,file="${defaultHeapDumpPath}" ${jvmPid}) ]]; then
  echo "⛔ The Dumper created no dumps. Check errors from kubectl. Wrong namespace/pod (${namespace}/${podIdentifier})?"
  exit 1
fi

echo "⏱  (2/6) Transferring heapdump over the wire from pod ${podIdentifier}"
kubectl cp -n "${namespace}" "${podIdentifier}":"${defaultHeapDumpPath}" "${defaultHeapFile}"
echo "⏱  (3/6) Removing heap dump on the pod ${podIdentifier}"
kubectl exec -n "${namespace}" "${podIdentifier}" -- rm "${defaultHeapDumpPath}"
echo "⏱  (4/6) Creating thread dump on the pod ${podIdentifier}"
kubectl exec -n "${namespace}" "${podIdentifier}" -- bash -c "jcmd ${jvmPid} Thread.print > ${defaultThreadDumpPath}"
echo "⏱  (5/6) Transferring thread dump over the wire from pod ${podIdentifier}"
kubectl cp -n "${namespace}" "${podIdentifier}":"${defaultThreadDumpPath}" "${defaultThreadFile}"
echo "⏱  (6/6) Removing thread dump on the pod ${podIdentifier}"
kubectl exec -n "${namespace}" "${podIdentifier}" -- rm "${defaultThreadDumpPath}"
echo -e "
Dumps transferred ✅
  @heap
    from => ${namespace}@${podIdentifier}:${defaultHeapDumpPath}
    to   => ${defaultHeapFile}
  @thread
    from => ${namespace}@${podIdentifier}:${defaultThreadDumpPath}
    to   => ${defaultThreadFile}
  Whats next? Open the file in JVisualVM or some other fancy tool to analyze the dumped file
"