k8s-java-dump.sh

k8s-java-dump.sh

#! /bin/sh
set -e

# 1. Collect kubernetes namespace and pod name from the user into variables
while getopts "n:p:" opt; do
  case $opt in
    n) NAMESPACE="$OPTARG" ;;
    p) POD="$OPTARG" ;;
    *) echo "Usage: $0 -n <namespace> -p <pod>"; exit 1 ;;
  esac
done

if [ -z "$NAMESPACE" ] || [ -z "$POD" ]; then
  echo "Usage: $0 -n <namespace> -p <pod>"
  exit 1
fi

# 2. Execute jcmd to get the process id of the first running java process in the pod
# Extract the PID from the numeric ID from the first line of the response into a variable
PID=$(kubectl exec -n "$NAMESPACE" "$POD" -- java -m jdk.jcmd/sun.tools.jcmd.JCmd | awk 'NR==1 {print $1}')
echo "🆔 Found java executable at PID $PID"

# 3. Extract the container's home directory
CONTAINER_HOME=$(kubectl exec -n "$NAMESPACE" "$POD" -- sh -c 'echo $HOME')
echo "🏠 Located container home $CONTAINER_HOME"

# 4. Using the process ID, dump a heap file
echo "🧠 Dumping java memory..."
kubectl exec -n "$NAMESPACE" "$POD" -- rm -f "$CONTAINER_HOME"/heap.bin
kubectl exec -n "$NAMESPACE" "$POD" -- java -m jdk.jcmd/sun.tools.jmap.JMap -dump:live,format=b,file="$CONTAINER_HOME"/heap.bin "$PID"

# 5. Download the heap dump locally
echo "⬇️  Downloading dump file..."
rm -f ./heap.bin
kubectl exec -n "$NAMESPACE" "$POD" -- base64 "$CONTAINER_HOME"/heap.bin | base64 -d > ./heap.bin
echo "✅ Download complete"