JaCoCo -- Extract coverage data from Kubernetes pods

jacoco_extract_data.sh

#!/usr/bin/env bash

set -e -u -o pipefail

if [ "${#}" -lt 4 ]; then
  echo "Usage: ${0} <path-to-jacococli.jar> <kubernetes-context> <kubernetes-namespace> <kubernetes-pod-selector>"
  echo "For selector syntax, see https://kubernetes.io/docs/concepts/overview/working-with-objects/labels."
  exit 1
fi

JACOCO_CLI_LOCAL="$(realpath "${1}")"
CONTEXT="${2}"
NAMESPACE="${3}"
POD_SELECTOR="${4}"

# All resources are stored in a temporary directory.
TMP_DIR='/tmp/jacoco-export'
mkdir -p "${TMP_DIR}"
pushd "${TMP_DIR}"

# Fetch coverage data from all pods.
kubectl get pods \
  --context="${CONTEXT}" \
  --namespace="${NAMESPACE}" \
  --selector="${POD_SELECTOR}" \
  --no-headers \
  -o custom-columns=":metadata.name" \
  | while read POD; do
    # One pod at a time, open a tunnel, connect to the JaCoCo agent to fetch
    # the coverage data and close the tunnel again.
    echo $CONTEXT - $POD
    (
      kubectl port-forward \
        --context="${CONTEXT}" \
        --namespace "${NAMESPACE}" \
        "${POD}" \
        "6300:6300" &
      trap "kill ${!}" ERR EXIT HUP INT TERM
      java -jar "${JACOCO_CLI_LOCAL}" dump --destfile "jacoco-${POD}.exec"
    )
  done

# Merge the coverage data into a single file.
java -jar "${JACOCO_CLI_LOCAL}" merge --destfile jacoco.exec jacoco-*.exec
popd