Setting an uptime alert

Cloning the sample app

The sample app is available on GitHub at GoogleCloudPlatform/getting-started-python .

1. Clone the repository.

     git 
    clone 
    https 
    : 
    // 
    github 
    . 
    com 
    / 
    GoogleCloudPlatform 
    / 
    getting 
    - 
    started 
    - 
    python 
    . 
    git 
    
   

2. Go to the sample directory.

     cd 
    getting 
    - 
    started 
    - 
    python 
    / 
    gce 
    
   

3. Because the app only returns "Hello World!", it requires no configuration, and you can run it right away.

     gcloud 
    app 
    deploy 
    
   

4. To see the returned message, enter the following URL in your browser:

   https:// PROJECT_ID . REGION_ID .r.appspot.com

   Replace the following:

   • PROJECT_ID : Your Google Cloud project ID
   • REGION_ID : A code that App Engine assigns to your app

Creating an uptime check

After you deploy your app, you can use Monitoring to create an uptime check. The check continually pings your deployed app to ensure that it's returning a healthy response.

1. In the Google Cloud console, go to the Uptime checks page:

   Go to Uptime checks

   If you use the search bar to find this page, then select the result whose subheading is Monitoring .

2. Click Create Uptime Check.

3. Give your check a title, such as Check Hello World , and then click Next.

4. In the Targetsection, you specify what the uptime check is to monitor:

   1. Because you deployed to App Engine, change Resource Typeto App Engineinstead of URL. ( URLis for generating a custom URL on a Compute Engine instance.)
   2. Select the Serviceto be monitored by the uptime check.
   3. Leave Pathblank to default to the main index page.
   4. Leave Check frequencyat the default of 1minute.
   5. Click Next.

5. Leave the Response Validationfields at their default values and click Next.

6. In the Alert & Notificationsection, you specify how you are notified if an alert occurs:

   • Ensure that the toggle's label is Alerting is enabled.
   • Leave the name and duration fields at their default values.

   • To add a notification channel to the alerting policy, in the text box labeled Notification channels, click Menu. Select the channels to add and click OK. The notifications are grouped alphabetically for each channel type.

     To add an entry to the checkbox list, click Manage notification channelsand follow the instructions. When you return to this dialog, click Refresh refresh .

7. Click Create. When the create action is successful, the message Check and alert createdis displayed and then the Uptime checksdashboard page is displayed.

   In the uptime checks dashboard, your new uptime check is listed. If you click the check name, then you open the detail view for that uptime check. This view displays several charts, shows the uptime percentage and the configuration information, and lists the configured alert policies. To view a policy, click its name.

   You can also view the alert policy by starting at the Alertingpage. From the alerting page, the Policiespane lists a subset of policies. To view a list of all policies, click See all policies.

Simulating an outage

Now that the uptime check is created, you can simulate an outage by changing your app to respond with an HTTP 404 Sorry, we can't find that page error rather than an HTTP 200 OK response.

1. The following code shows where the Hello World app returns only a 'Hello World!' message, and that the status code of the response defaults to 200 OK . To view this code in the Hello World app, use the view function.

     # Copyright 2019 Google LLC 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. 
    from 
     
    flask 
     
    import 
    Flask 
    app 
    = 
    Flask 
    ( 
    __name__ 
    ) 
    @app 
    . 
    route 
    ( 
    '/' 
    , 
    methods 
    = 
    [ 
    'GET' 
    ]) 
    def 
     
    say_hello 
    (): 
    return 
    "Hello, world!" 
    if 
    __name__ 
    == 
    '__main__' 
    : 
    app 
    . 
    run 
    ( 
    host 
    = 
    '127.0.0.1' 
    , 
    port 
    = 
    8080 
    , 
    debug 
    = 
    True 
    ) 
    
   

2. To cause the Hello World app to return an HTTP 404 error code, change the return line by adding a 404 value to the second part of the return value.

    return 
     
    'Hello World' 
   ,  
    404 
   

3. Deploy the new, intentionally broken app.

   gcloud  
   app  
   deploy

   Within half an hour, you'll receive an email message that states that your uptime check is failing.