<p>I have a container that keeps crashing in my k8s cluster for unknown reasons. The container's process is an nginx server. The container appears to be receiving a SIGQUIT signal.</p>
<h5>Dockerfile</h5>
<pre><code># build environment
FROM node:16-alpine as build
WORKDIR /app
ENV PATH /app/node_modules/.bin:$PATH
COPY package.json ./
COPY package-lock.json ./
RUN npm ci --silent
RUN npm install react-scripts@3.4.1 -g --silent
COPY . ./
RUN npm run build

# production environment
FROM nginx:stable-alpine
COPY --from=build /app/build /usr/share/nginx/html
EXPOSE 80
CMD [&quot;nginx&quot;, &quot;-g&quot;, &quot;daemon off;&quot;]
</code></pre>
<h5>container logs</h5>
<pre><code>/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2021/11/11 06:40:37 [notice[] 1#1: using the &quot;epoll&quot; event method
2021/11/11 06:40:37 [notice[] 1#1: nginx/1.20.1
2021/11/11 06:40:37 [notice[] 1#1: built by gcc 10.2.1 20201203 (Alpine 10.2.1_pre1) 
2021/11/11 06:40:37 [notice[] 1#1: OS: Linux 5.4.120+
2021/11/11 06:40:37 [notice[] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2021/11/11 06:40:37 [notice[] 1#1: start worker processes
2021/11/11 06:40:37 [notice[] 1#1: start worker process 32
2021/11/11 06:40:37 [notice[] 1#1: start worker process 33
10.15.128.65 - - [11/Nov/2021:06:40:41 +0000] &quot;\x16\x03\x01\x01\x00\x01\x00\x00\xFC\x03\x03&gt;\x85O#\xCC\xB9\xA5j\xAB\x8D\xC1PpZ\x18$\xE5ah\xDF7\xB1\xFF\xAD\x22\x050\xC3.+\xB6+ \x0F}S)\xC9\x1F\x0BY\x15_\x10\xC6\xAAF\xAA\x9F\x9E_@dG\x01\xF5vzt\xB50&amp;;\x1E\x15\x00&amp;\xC0/\xC00\xC0+\xC0,\xCC\xA8\xCC\xA9\xC0\x13\xC0\x09\xC0\x14\xC0&quot; 400 157 &quot;-&quot; &quot;-&quot; &quot;-&quot;
10.15.128.65 - - [11/Nov/2021:06:40:44 +0000] &quot;\x16\x03\x01\x01\x00\x01\x00\x00\xFC\x03\x03\xD8['\xE75x'\xC3}+v\xC9\x83\x84\x96EKn\xC5\xB6}\xEE\xBE\xD9Gp\xE9\x1BX&lt;n\xB2 \xD9n\xD1\xC5\xFC\xF2\x8D\x92\xAC\xC0\xA8mdF\x17B\xA3y9\xDD\x98b\x0E\x996\xB6\xA5\xAB\xEB\xD4\xDA&quot; 400 157 &quot;-&quot; &quot;-&quot; &quot;-&quot;
10.15.128.65 - - [11/Nov/2021:06:40:47 +0000] &quot;\x16\x03\x01\x01\x00\x01\x00\x00\xFC\x03\x03Fy\x03N\x0E\x11\x89k\x7F\xC5\x00\x90w}\xEB{\x7F\xB1=\xF0&quot; 400 157 &quot;-&quot; &quot;-&quot; &quot;-&quot;
2021/11/11 06:40:47 [notice[] 1#1: signal 3 (SIGQUIT) received, shutting down
2021/11/11 06:40:47 [notice[] 32#32: gracefully shutting down
2021/11/11 06:40:47 [notice[] 32#32: exiting
2021/11/11 06:40:47 [notice[] 33#33: gracefully shutting down
2021/11/11 06:40:47 [notice[] 32#32: exit
2021/11/11 06:40:47 [notice[] 33#33: exiting
2021/11/11 06:40:47 [notice[] 33#33: exit
2021/11/11 06:40:47 [notice[] 1#1: signal 17 (SIGCHLD) received from 33
2021/11/11 06:40:47 [notice[] 1#1: worker process 33 exited with code 0
2021/11/11 06:40:47 [notice[] 1#1: signal 29 (SIGIO) received
2021/11/11 06:40:47 [notice[] 1#1: signal 17 (SIGCHLD) received from 32
2021/11/11 06:40:47 [notice[] 1#1: worker process 32 exited with code 0
2021/11/11 06:40:47 [notice[] 1#1: exit
</code></pre>
<h5>kubectl get pod PODNAME --output=yaml</h5>
<pre><code>apiVersion: v1
kind: Pod
metadata:
  annotations:
    seccomp.security.alpha.kubernetes.io/pod: runtime/default
  creationTimestamp: &quot;2021-11-11T06:40:30Z&quot;
  generateName: sgb-web-master-fb9f995fb-
  labels:
    app: sgb-web-master
    pod-template-hash: fb9f995fb
  name: sgb-web-master-fb9f995fb-zwhgl
  namespace: default
  ownerReferences:
  - apiVersion: apps/v1
    blockOwnerDeletion: true
    controller: true
    kind: ReplicaSet
    name: sgb-web-master-fb9f995fb
    uid: 96ebf43d-e2e6-4632-a536-764bcab8daeb
  resourceVersion: &quot;66168456&quot;
  uid: ed80b0d0-6681-4c2a-8edd-16c8ef6bee86
spec:
  containers:
  - env:
    - name: PORT
      value: &quot;80&quot;
    image: cflynnus/saigonbros-web:master-d70f3001d130bf986da236a08e1fded4b64e8097
    imagePullPolicy: Always
    livenessProbe:
      failureThreshold: 3
      httpGet:
        path: /
        port: 80
        scheme: HTTPS
      initialDelaySeconds: 3
      periodSeconds: 3
      successThreshold: 1
      timeoutSeconds: 1
    name: saigonbros-web
    ports:
    - containerPort: 80
      name: sgb-web-port
      protocol: TCP
    resources:
      limits:
        cpu: 500m
        ephemeral-storage: 1Gi
        memory: 2Gi
      requests:
        cpu: 500m
        ephemeral-storage: 1Gi
        memory: 2Gi
    securityContext:
      capabilities:
        drop:
        - NET_RAW
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-rkwb2
      readOnly: true
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  nodeName: gk3-autopilot-cluster-1-default-pool-43dd48b9-tf0n
  preemptionPolicy: PreemptLowerPriority
  priority: 0
  readinessGates:
  - conditionType: cloud.google.com/load-balancer-neg-ready
  restartPolicy: Always
  schedulerName: gke.io/optimize-utilization-scheduler
  securityContext:
    seccompProfile:
      type: RuntimeDefault
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - name: kube-api-access-rkwb2
    projected:
      defaultMode: 420
      sources:
      - serviceAccountToken:
          expirationSeconds: 3607
          path: token
      - configMap:
          items:
          - key: ca.crt
            path: ca.crt
          name: kube-root-ca.crt
      - downwardAPI:
          items:
          - fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace
            path: namespace
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: null
    message: 'Pod is in NEG &quot;Key{\&quot;k8s1-301c19bd-default-sgb-web-master-80-48ae70f6\&quot;,
      zone: \&quot;asia-southeast1-a\&quot;}&quot;. NEG is not attached to any BackendService with
      health checking. Marking condition &quot;cloud.google.com/load-balancer-neg-ready&quot;
      to True.'
    reason: LoadBalancerNegWithoutHealthCheck
    status: &quot;True&quot;
    type: cloud.google.com/load-balancer-neg-ready
  - lastProbeTime: null
    lastTransitionTime: &quot;2021-11-11T06:40:33Z&quot;
    status: &quot;True&quot;
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: &quot;2021-11-11T06:44:42Z&quot;
    message: 'containers with unready status: [saigonbros-web]'
    reason: ContainersNotReady
    status: &quot;False&quot;
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: &quot;2021-11-11T06:44:42Z&quot;
    message: 'containers with unready status: [saigonbros-web]'
    reason: ContainersNotReady
    status: &quot;False&quot;
    type: ContainersReady
  - lastProbeTime: null
    lastTransitionTime: &quot;2021-11-11T06:40:33Z&quot;
    status: &quot;True&quot;
    type: PodScheduled
  containerStatuses:
  - containerID: containerd://dfc32581c1edda1a221dc00cede918cfb93225e51e505ea7a9f935fc9ab893d5
    image: docker.io/cflynnus/saigonbros-web:master-d70f3001d130bf986da236a08e1fded4b64e8097
    imageID: docker.io/cflynnus/saigonbros-web@sha256:ff8d6d42511ed6520967007714dfbd46817fca06bb65ae984bc04a8b90346222
    lastState:
      terminated:
        containerID: containerd://dfc32581c1edda1a221dc00cede918cfb93225e51e505ea7a9f935fc9ab893d5
        exitCode: 0
        finishedAt: &quot;2021-11-11T06:44:41Z&quot;
        reason: Completed
        startedAt: &quot;2021-11-11T06:44:30Z&quot;
    name: saigonbros-web
    ready: false
    restartCount: 6
    started: false
    state:
      waiting:
        message: back-off 2m40s restarting failed container=saigonbros-web pod=sgb-web-master-fb9f995fb-zwhgl_default(ed80b0d0-6681-4c2a-8edd-16c8ef6bee86)
        reason: CrashLoopBackOff
  hostIP: 10.148.15.200
  phase: Running
  podIP: 10.15.128.103
  podIPs:
  - ip: 10.15.128.103
  qosClass: Guaranteed
  startTime: &quot;2021-11-11T06:40:33Z&quot;
</code></pre>

<p>Your liveness probe is configured as <code>HTTPS</code> on port 80. Just change it to <code>HTTP</code>. Look at the key <code>spec.containers.livenessProbe.httpGet.scheme</code>.</p>
<p>Kubernetes thinks that your pod isn't alive (bad liveness probe) and cause the SIGQUIT.<br />
Normally this will help you. When your pod isn't alive, then Kubernetes tries to restart the app for you.</p>
<hr />
<h3>Edit</h3>
<p>You can also identify that behavior in the logs of your nginx:</p>
<pre><code>10.15.128.65 - - [11/Nov/2021:06:40:41 +0000] &quot;\x16\x03\x01\x01\x00\x01\x00\x00\xFC\x03\x03&gt;\x85O#\xCC\xB9\xA5j\xAB\x8D\xC1PpZ\x18$\xE5ah\xDF7\xB1\xFF\xAD\x22\x050\xC3.+\xB6+ \x0F}S)\xC9\x1F\x0BY\x15_\x10\xC6\xAAF\xAA\x9F\x9E_@dG\x01\xF5vzt\xB50&amp;;\x1E\x15\x00&amp;\xC0/\xC00\xC0+\xC0,\xCC\xA8\xCC\xA9\xC0\x13\xC0\x09\xC0\x14\xC0&quot; 400 157 &quot;-&quot; &quot;-&quot; &quot;-&quot;
10.15.128.65 - - [11/Nov/2021:06:40:44 +0000] &quot;\x16\x03\x01\x01\x00\x01\x00\x00\xFC\x03\x03\xD8['\xE75x'\xC3}+v\xC9\x83\x84\x96EKn\xC5\xB6}\xEE\xBE\xD9Gp\xE9\x1BX&lt;n\xB2 \xD9n\xD1\xC5\xFC\xF2\x8D\x92\xAC\xC0\xA8mdF\x17B\xA3y9\xDD\x98b\x0E\x996\xB6\xA5\xAB\xEB\xD4\xDA&quot; 400 157 &quot;-&quot; &quot;-&quot; &quot;-&quot;
10.15.128.65 - - [11/Nov/2021:06:40:47 +0000] &quot;\x16\x03\x01\x01\x00\x01\x00\x00\xFC\x03\x03Fy\x03N\x0E\x11\x89k\x7F\xC5\x00\x90w}\xEB{\x7F\xB1=\xF0&quot; 400 157 &quot;-&quot; &quot;-&quot; &quot;-&quot;
2021/11/11 06:40:47 [notice[] 1#1: signal 3 (SIGQUIT) received, shutting down
</code></pre>
<p>There are the three configured liveness probes with a period of three seconds. They are unreadable, because kubernetes send TLS packets (which are in a plain-view not human readable).<br />
Immediately after that, there is the shutdown.</p>
<p>The other way is to read the description of your pod. There you can see, that <code>HTTPS</code> and port 80 are configured. <code>HTTPS</code> runs over port 443, so it must be a configuration error.</p>
