Making sure the deployment works fine

Our function deployed without any hassle, but how do we ensure that whole system is behaving correctly? To ensure everything is working fine, we can provide CodeDeploy with a list of variables to track during the deployment process, then cancel it, and shift all the traffic to the old version if the ALARM is triggered. With serverless, we can set the alarm using another plugin. Let's have a look at how to do this: 

1. Update the serverless.yml to set the alarm, as shown in the following code: 

service: my-canary-deployment
provider:
 name: aws
 runtime: nodejs6.10

plugins:
    - serverless-plugin-aws-alerts
    - serverless-plugin-canary-deployments

custom:
    alerts:
        dashboards: true

functions:
    hello:
         handler: handler.hello
         events:
             - http: get hello
         alarms:
             - name: test
                 namespace: 'AWS/Lambda'
                 metric: Errors
                 threshold: 1
                 statistic: Minimum
                 period: 60
                 evaluationPeriods: 1
                 comparisonOperator: GreaterThanOrEqualToThreshold
         deploymentSettings:
             type: Linear10PercentEvery1Minute
             alias: Live
             alarms:
                 - HelloTestAlarm

2. Let's deploy the function and see how it works, as shown in the following code: 

$ serverless deploy -v

Serverless: Packaging service...
Serverless: Excluding development dependencies...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading artifacts...
Serverless: Uploading service .zip file to S3 (611 B)...
Serverless: Validating template...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
CloudFormation - UPDATE_IN_PROGRESS - AWS::CloudFormation::Stack - my-canary-deployment-dev
CloudFormation - CREATE_IN_PROGRESS - AWS::CloudWatch::Dashboard - AlertsDashboard
CloudFormation - UPDATE_IN_PROGRESS - AWS::Lambda::Function - HelloLambdaFunction
CloudFormation - UPDATE_COMPLETE - AWS::Lambda::Function - HelloLambdaFunction
CloudFormation - CREATE_IN_PROGRESS - AWS::CloudWatch::Alarm - HelloTestAlarm
CloudFormation - CREATE_IN_PROGRESS - AWS::CloudWatch::Alarm - HelloTestAlarm
CloudFormation - CREATE_IN_PROGRESS - AWS::Lambda::Version - HelloLambdaVersionja19jdYXntxmsiUagZLZfDEMTshQJ8ApOagyYwmXE
CloudFormation - CREATE_COMPLETE - AWS::CloudWatch::Alarm - HelloTestAlarm
CloudFormation - CREATE_IN_PROGRESS - AWS::Lambda::Version - HelloLambdaVersionja19jdYXntxmsiUagZLZfDEMTshQJ8ApOagyYwmXE
CloudFormation - CREATE_COMPLETE - AWS::Lambda::Version - HelloLambdaVersionja19jdYXntxmsiUagZLZfDEMTshQJ8ApOagyYwmXE
CloudFormation - CREATE_IN_PROGRESS - AWS::CloudWatch::Dashboard - AlertsDashboard
CloudFormation - CREATE_COMPLETE - AWS::CloudWatch::Dashboard - AlertsDashboard
CloudFormation - UPDATE_IN_PROGRESS - AWS::CodeDeploy::DeploymentGroup - HelloLambdaFunctionDeploymentGroup
CloudFormation - UPDATE_COMPLETE - AWS::CodeDeploy::DeploymentGroup - HelloLambdaFunctionDeploymentGroup
CloudFormation - UPDATE_IN_PROGRESS - AWS::Lambda::Alias - HelloLambdaFunctionAliasLive
CloudFormation - UPDATE_IN_PROGRESS - AWS::Lambda::Alias - HelloLambdaFunctionAliasLive
CloudFormation - UPDATE_COMPLETE - AWS::Lambda::Alias - HelloLambdaFunctionAliasLive
CloudFormation - CREATE_IN_PROGRESS - AWS::ApiGateway::Deployment - ApiGatewayDeployment1530403890255
CloudFormation - CREATE_IN_PROGRESS - AWS::ApiGateway::Deployment - ApiGatewayDeployment1530403890255
CloudFormation - CREATE_COMPLETE - AWS::ApiGateway::Deployment - ApiGatewayDeployment1530403890255
CloudFormation - UPDATE_COMPLETE_CLEANUP_IN_PROGRESS - AWS::CloudFormation::Stack - my-canary-deployment-dev
CloudFormation - DELETE_IN_PROGRESS - AWS::ApiGateway::Deployment - ApiGatewayDeployment1530401797330
CloudFormation - DELETE_COMPLETE - AWS::ApiGateway::Deployment - ApiGatewayDeployment1530401797330
CloudFormation - DELETE_SKIPPED - AWS::Lambda::Version - HelloLambdaVersionW59z2S8rIu6lAv3dCyvgKLndpEosDs1l1kpbg6Lrg
CloudFormation - UPDATE_COMPLETE - AWS::CloudFormation::Stack - my-canary-deployment-dev

The deploy step will create an alarm in CodeDeploy and the CloudWatch dashboard, where we can see different graphs representing invocations and errors. You can log into AWS Console and go to CodeDeploy and CloudWatch to see how the alarm is created, and to see what the dashboard looks like.