AwsLambdaWebsiteMonitoring.md

Website monitoring using AWS

Basic instructions on how to use AWS for monitoring your websites. Note that I did not include instructions on creating the SNS topic, but check out the link in the Resources section for instructions on that one.

Creating a monitoring function

1. Go to Lambda
2. Click on Create Function button
3. Select a function from a lambda-canary blueprint
4. Enter a name like check_AzuriteMaps
5. Choose an existing role, service-role/lambda_canary_role
6. Under the Rule, select the one_minute rule
7. Enable the trigger
8. Leave the function code as it is
9. Under the site enivornment variable, enter the URL of the site
10. Under the 'expected`enivornment variable, enter the expected text on that site
11. Click on the Create Function button

Creating a new alarm

The following instructions will create an alarm that will run each minute and when it detects the website is down, it will send an email to the email address previously configured in the SNS topic Websites_status_alarms. It will only send this email once during the same failure (it will not repeat the emails after one minute). Once the website is up again, it will send a new email stating the alarm is now OK.

1. Go to CloudWatch
2. Click on the Alarms in the left menu.
3. Click on the Create Alarm button.
4. In the 1. Select Metric upper tab, in the Browse Metric combo box, select Lambda and then, under the Lambda > By Function Name, find appropriate function name (like check_azuritemaps) and choose Errors metric name.
5. Click on the 2. Define Alarm tab at the top of the dialog.
6. Name should be something that easily identifies which website is down (like AzuriteMaps is down).
7. Set Whenever to >= 1 (leave the default for 1 out of 1 datapoints).
8. Under Actions section, we will add two notifications (one for when the alarm is triggered and another for when the alarm is back to OK status): a. 'Whenever this alarm' should have State is ALARM. b. Send notification to should have Websites_status_alarms (a SNS topic which we previously configured to send email to our email address). c. Click on +Notification button and add another alarm, this time with State is OK
9. Period should be 1 minute.
10. Statistic: Standard, Average

Wait for one minute and then check the status of the alarm.

To repeat the procedure for other websites, you can easily copy the existing alarm definition and just change the targeted lambda function and the name of the alarm.

Disabling a Lambda function

1. On the Lambda function editing page, click on the CloudWatch Events box to open the events editor.
2. A list of events (or just one event called one_minute in this case) will be shown below. Uncheck the Enabled checkbox to the right of the event.
3. Save the edited Lambda function.

Resources

• Using AWS Lambda to check if your website is online: this one describes writing the NodeJS lambda function, but I find the existing lambda-canary blueprint quite enough.