"Cloud Run error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable."

Question

I'm trying to build a container image that I will later use to update the code inside of a virtual machine. The docker image works fine as I can build and run it inside of my terminal. However, I keep getting an error when I try to deploy it to cloud run: "Cloud Run error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable." How can I fix this error?

The build log contains this:

Deploying container to Cloud Run service [SERVICE] in project [PROJECT_ID] region [REGION]
Deploying...
Creating Revision.......................................................................................................................................................................failed
Deployment failed
ERROR: (gcloud.run.deploy) Cloud Run error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable. Logs for this revision might contain more information.

The revision log contains this:

{
  "protoPayload": {
    "@type": "type.googleapis.com/google.cloud.audit.AuditLog",
    "status": {
      "code": 9,
      "message": "Ready condition status changed to False for Revision {REVISION_NAME} with message: Cloud Run error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable. Logs for this revision might contain more information.\n\nLogs URL:{URL_LINK}"
    },
    "serviceName": "run.googleapis.com",
    "resourceName": "{REVISION_NAME}",
    "response": {
      "metadata": {
        "name": "{REVISION_NAME}",
        "namespace": "{NAMESPACE}",
        "selfLink": "{SELFLINK}",
        "uid": "{UID}",
        "resourceVersion": "{RESOURCEVER}",
        "generation": 1,
        "creationTimestamp": "{TIMESTAMP}",
        "labels": {
          "serving.knative.dev/route": "{SERVICE}",
          "serving.knative.dev/configuration": "{SERVICE}",
          "serving.knative.dev/configurationGeneration": "15",
          "serving.knative.dev/service": "{SERVICE}",
          "serving.knative.dev/serviceUid": "{SERVICE_UID}",
          "cloud.googleapis.com/location": "{REGION}"
        },
        "annotations": {
          "run.googleapis.com/client-name": "gcloud",
          "serving.knative.dev/creator": "{NAMESPACE}@cloudbuild.gserviceaccount.com",
          "client.knative.dev/user-image": "gcr.io/{PROJECT_ID}/{IMAGE}",
          "run.googleapis.com/client-version": "357.0.0",
          "autoscaling.knative.dev/maxScale": "100"
        },
        "ownerReferences": [
          {
            "kind": "Configuration",
            "name": "{SERVICE}",
            "uid": "{UID}",
            "apiVersion": "serving.knative.dev/v1",
            "controller": true,
            "blockOwnerDeletion": true
          }
        ]
      },
      "apiVersion": "serving.knative.dev/v1",
      "kind": "Revision",
      "spec": {
        "containerConcurrency": 80,
        "timeoutSeconds": 300,
        "serviceAccountName": "{NAMESPACE}[email protected]",
        "containers": [
          {
            "image": "gcr.io/{PROJECT_ID}/{IMAGE}",
            "ports": [
              {
                "name": "h2c",
                "containerPort": 8080
              }
            ],
            "resources": {
              "limits": {
                "cpu": "1000m",
                "memory": "512Mi"
              }
            }
          }
        ]
      },
      "status": {
        "observedGeneration": 1,
        "conditions": [
          {
            "type": "Ready",
            "status": "False",
            "reason": "HealthCheckContainerError",
            "message": "Cloud Run error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable. Logs for this revision might contain more information.\n\nLogs URL:{LOG_LINK}",
            "lastTransitionTime": "{TIME}"
          },
          {
            "type": "Active",
            "status": "Unknown",
            "reason": "Reserve",
            "lastTransitionTime": "{TIME}",
            "severity": "Info"
          },
          {
            "type": "ContainerHealthy",
            "status": "False",
            "reason": "HealthCheckContainerError",
            "message": "Cloud Run error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable. Logs for this revision might contain more information.\n\nLogs URL:{LOG_LINK}",
            "lastTransitionTime": "{TIME}"
          },
          {
            "type": "ResourcesAvailable",
            "status": "True",
            "lastTransitionTime": "{TIME}"
          },
          {
            "type": "Retry",
            "status": "True",
            "reason": "ImmediateRetry",
            "message": "System will retry after 0:00:00 from lastTransitionTime for attempt 0.",
            "lastTransitionTime": "{TIME}",
            "severity": "Info"
          }
        ],
        "logUrl": "{LOG_LINK}",
        "imageDigest": "gcr.io/{PROJECT_ID}/{IMAGE_SHA}"
      },
      "@type": "type.googleapis.com/google.cloud.run.v1.Revision"
    }
  },
  "insertId": "{ID}",
  "resource": {
    "type": "cloud_run_revision",
    "labels": {
      "location": "{REGION}",
      "configuration_name": "{SERVICE}",
      "service_name": "{SERVICE}",
      "project_id": "{PROJECT_ID}",
      "revision_name": "{REVISION_NAME}"
    }
  },
  "timestamp": "{TIME}",
  "severity": "ERROR",
  "logName": "projects/{PROJECT_ID}/logs/cloudaudit.googleapis.com%2Fsystem_event",
  "receiveTimestamp": "{TIME}"
}

This is my cloudbuild.yaml:

steps:
- name: 'gcr.io/cloud-builders/docker'
  args: ['build', '-t', 'gcr.io/PROJECT_ID/IMAGE', '.']
- name: 'gcr.io/cloud-builders/docker'
  args: ['push', 'gcr.io/PROJECT_ID/IMAGE']
- name: 'gcr.io/google.com/cloudsdktool/cloud-sdk'
  entrypoint: gcloud
  args: ['run', 'deploy', 'SERVICE-NAME', '--image', 'gcr.io/PROJECT_ID/IMAGE', '--region', 'REGION', '--port', '8080']
images:
- gcr.io/PROJECT_ID/IMAGE

This is my Dockerfile:

FROM python:3.9.7-slim-buster

WORKDIR /app

COPY . .

CMD [ "python3", "hello.py" ]

This is the code in hello.py:

print("Hello World")

Answer 1

When Cloud Run starts your container, a health check is sent to the container. Your container is not responding to the health check. Therefore, Cloud Run determines that your service is failing.

Cloud Run requires that a container provide service/process/program that listens for and responds to HTTP requests.

Your hello.py file only prints a message to stdout. Your program does not start a process to listen for requests.

A very simple example that converts your example into a working program:

import os

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
        return "Hello world"

if __name__ == '__main__':
        app.run(debug=True, host='0.0.0.0', port=int(os.environ.get('PORT', 8080)))

Note: You will need to add a file requirements.txt to your build to include Flask. Create requirements.txt in the same location as Dockerfile.

requirements.txt:

Flask==2.0.1