[Automation] - Stop the runner image build writing cache it never reads

cypress/jenkins/Jenkinsfile

@@ -1,7 +1,7 @@
 #!groovy
 // Jenkinsfile — CI pipeline for Rancher Dashboard E2E tests
 //
-// Stages: Pre-Clean → Preflight → Checkout → Run Tests → Grab Results
+// Stages: Pre-Clean → Preflight → Checkout → Disk → Run Tests → Grab Results
 //   finally: Clean Test Environment → Cleanup Executor → Test Report
 
 def branch = "${env.BRANCH}" != 'null' && "${env.BRANCH}" != '' ? "${env.BRANCH}" : 'master'
@@ -68,6 +68,10 @@ node('harvester-vpn-1') {
                 ])
                 // init.sh clones qa-infra-automation at runtime
               }
+              // In the repo, so it cannot run before Checkout.
+              stage('Disk') {
+                sh 'cypress/jenkins/disk-report.sh before'
+              }
               stage('Run Tests') {
                 timeout(time: 180, unit: 'MINUTES') {
                   testExitCode = sh(script: 'cypress/jenkins/init.sh', returnStatus: true)
@@ -112,6 +116,9 @@ node('harvester-vpn-1') {
                   rm -f "${WORKSPACE}/qa-infra-automation/ansible/testing/dashboard-e2e/vars.yaml" 2>/dev/null || true
                   rm -f "${WORKSPACE}/qa-infra-automation/ansible/testing/dashboard-e2e/.env" 2>/dev/null || true
                 """
+                if (fileExists('cypress/jenkins/disk-report.sh')) {
+                  sh 'cypress/jenkins/disk-report.sh after'
+                }
               }
               try {
                 stage('Test Report') {

cypress/jenkins/disk-report.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+#
+# disk-report.sh <before|after> - report agent disk usage around a build.
+#
+# The agent's disk is shared by every executor and by other jobs, and nothing
+# reports what a build costs it. This prints a few lines at each end of a build
+# so growth is attributable to the build that caused it.
+#
+# Read only, apart from a counter under /tmp used to print the delta.
+#
+set -uo pipefail
+
+DISK_PHASE="${1:?usage: disk-report.sh <before|after>}"
+
+ws="${WORKSPACE:-$PWD}"
+tag="[disk:${DISK_PHASE}]"
+stamp="/tmp/jenkins-disk-${EXECUTOR_NUMBER:-0}.before"
+
+avail_kb=$(df -P "$ws" 2>/dev/null | awk 'NR==2 {print $4}')
+avail_kb=${avail_kb:-0}
+
+# The preflight guard measures the workspace, which may not be where images and
+# cache actually live.
+root=$(docker info --format '{{.DockerRootDir}}' 2>/dev/null)
+if [ -n "$root" ]; then
+  df -P "$root" 2>/dev/null |
+    awk -v t="${tag}" -v r="$root" 'NR==2 {print t " docker root " r ": " int($4/1024/1024) "GB free of " int($2/1024/1024) "GB"}'
+else
+  df -P "$ws" 2>/dev/null |
+    awk -v t="${tag}" 'NR==2 {print t " workspace: " int($4/1024/1024) "GB free of " int($2/1024/1024) "GB"}'
+fi
+
+# Totals rather than a catalogue. A build that reuses cached layers leaves these
+# unchanged, so a jump between the two phases is this build's doing.
+#
+# Counted from the end because the type name is one word or two, and the
+# percentage suffix on RECLAIMABLE is stripped first so every row has the same
+# shape.
+docker system df 2>/dev/null | sed 's/ ([0-9]*%)//' |
+  awk -v t="${tag}" '
+    $1 == "Images" || $1 == "Containers" { printf "%s %-11s %9s total, %9s reclaimable\n", t, $1, $(NF-1), $NF }
+    $1 == "Build"                        { printf "%s %-11s %9s total, %9s reclaimable\n", t, "BuildCache", $(NF-1), $NF }' ||
+  echo "${tag} docker unavailable"
+
+if [ "${DISK_PHASE}" = "before" ]; then
+  echo "${avail_kb}" > "${stamp}" 2>/dev/null || true
+elif [ -f "${stamp}" ]; then
+  before_kb=$(cat "${stamp}" 2>/dev/null || echo 0)
+  if [ "${before_kb}" -gt 0 ] 2>/dev/null; then
+    # Other executors share the disk, so this is net movement rather than this
+    # build's own footprint, and may be negative.
+    delta_mb=$(( (before_kb - avail_kb) / 1024 ))
+    if [ "${delta_mb}" -ge 0 ]; then
+      echo "${tag} net change over this build: ${delta_mb}MB consumed"
+    else
+      echo "${tag} net change over this build: $(( -delta_mb ))MB released"
+    fi
+  fi
+  rm -f "${stamp}" 2>/dev/null || true
+fi
+exit 0

cypress/jenkins/init.sh

@@ -38,10 +38,14 @@ clone_qa_infra() {
   echo "[init] qa-infra-automation (${QA_INFRA_BRANCH}) at $(git -C "${QA_INFRA_DIR}" rev-parse --short HEAD)"
 }
 
-# Build the runner image from Dockerfile.quickstart
+# Build the runner image from Dockerfile.quickstart.
+#
+# Cached rather than --no-cache: Pre-Clean removes this tag every build, so the
+# image is rebuilt regardless, and --no-cache only added a cold build plus a
+# BuildKit cache record per layer that nothing on the agent reclaims.
 build_runner_image() {
   echo "[init] Building ${RUNNER_IMAGE} image..."
-  docker build -q --no-cache -f "${PLAYBOOK_DIR}/Dockerfile.quickstart" \
+  docker build -q -f "${PLAYBOOK_DIR}/Dockerfile.quickstart" \
     -t "${RUNNER_IMAGE}" "${PLAYBOOK_DIR}"
 }