alexamies · March 12, 2020 18:13 · Mar 12, 2020
diff --git a/README.md b/README.md
@@ -0,0 +1,51 @@
+# How to debug an unresponsive App Engine Flex app
+
+You can debug an unhealthy app using Google Cloud Logging and other GCP tools
+even if the app has become unresponsive. A test app is provided that simulates
+the problem in an experiment for the purpose of explaining the debugging process
+with App Engine Flex.
+
+Prerequisites:
+1. GCP Project with billing enabled
+2. Google Cloud SDK installed
+
+The app randomly stalls on incoming requests by going to sleep.
+
+Follow these steps to deploy and run the app.
+
+Set your project as the default in gcloud
+
+```shell
+GOOGLE_CLOUD_PROJECT=[Your project]
+gcloud config set project $GOOGLE_CLOUD_PROJECT
+```
+
+Enable App Engine
+
+```shell
+gcloud app create
+```
+
+Deploy the app
+
+```shell
+gcloud app deploy
+```
+
+Browse to the app
+
+```shell
+gcloud app browse
+```
+
+Set up Apache Bench In the Cloud Shell or Linux command line
+
+```shell
+sudo apt-get install apache2-utils
+```
+
+Send some requests to your app
+
+```shell
+ab -n 1000 -c 5 https://${GOOGLE_CLOUD_PROJECT}.appspot.com/
+```
diff --git a/an_unhealthy_app_demo.md b/an_unhealthy_app_demo.md
@@ -0,0 +1,3 @@
+# How to debug an unresponsive App Engine Flex app
+
+See the README.md for details on how to run this
diff --git a/app.yaml b/app.yaml
@@ -0,0 +1,18 @@
+runtime: python
+env: flex
+entrypoint: gunicorn -b :$PORT main:app
+runtime_config:
+  python_version: 3
+manual_scaling:
+  instances: 1
+resources:
+  cpu: 1
+  memory_gb: 0.5
+  disk_size_gb: 10
+readiness_check:
+  path: "/readiness_check"
+  check_interval_sec: 5
+  timeout_sec: 4
+  failure_threshold: 2
+  success_threshold: 2
+  app_start_timeout_sec: 300
diff --git a/main.py b/main.py
@@ -0,0 +1,75 @@
+# Copyright 2020 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Simulate an unhealthy app for demonstration of troubleshooting"""
+
+import logging
+import random
+import sys
+import time
+from flask import Flask, g
+
+
+app = Flask(__name__)
+
+
+def get_app_healthy() -> bool:
+  """Get the application health"""
+  if 'app_healthy' not in g:
+    g.app_healthy = True
+  return g.app_healthy
+
+
+def set_app_healthy(value: bool):
+  """Set the application health"""
+  if 'app_healthy' not in g:
+    g.app_healthy = value
+  g.app_healthy = value
+
+
+@app.route('/')
+def home():
+  """1 out of 20 requests change the app to an unhealthy state"""
+  msg = 'Welcome to the home page!\n'
+  if not get_app_healthy():
+    msg = 'Changing to an unhealthy state'
+    logging.error(msg)
+    #sys.exit(1) # exit the process
+    time.sleep(90) # seconds
+    return msg
+  r = random.uniform(0.0, 1.0)
+  if r > 0.95:
+    msg = 'App is unhealthy'
+    logging.error(msg)
+    set_app_healthy(False)
+    time.sleep(90) # seconds
+  return msg
+
+
+@app.route('/readiness_check')
+def readiness_check():
+  #Respond to the load balancer's readiness check
+  msg = 'OK\n'
+  r = random.uniform(0.0, 1.0)
+  if r > 0.9:
+    msg = 'App is refuses to start'
+    logging.error(msg)
+    sys.exit(1)
+  return msg
+
+
+if __name__ == '__main__':
+  logging.basicConfig(level=logging.INFO)
+  logging.info('Starting up')
+  app.run(host='127.0.0.1', port=8080)
diff --git a/requirements.txt b/requirements.txt
@@ -0,0 +1,2 @@
+Flask==1.1.1
+gunicorn==20.0.4
Original file line number	Diff line number	Diff line change
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		# How to debug an unresponsive App Engine Flex app

		See the README.md for details on how to run this