Setting up AlertManager

Create Lambda function

Go to Lambda > Create a Lambda function > Blank function.
Do not configure any triggers at this time (just hit next).
Name: AlertManager
Description: AlertManager main: ingestor & alerter
Runtime: Node.js 4.3
Code entry type: Upload a .ZIP file
Download latest alertmanager.zip from releases -page (in GitHub) to your desktop and then upload to Lambda

Env variables:

ALERT_TOPIC = ARN of your alert topic (mine looked like arn:aws:sns:us-west-2:426466625513:AlertManager-alert)

Role config:

Handler: leave as is
Role: leave as is (Choose existing role)
Existing role: AlertManager

Advanced config:

Memory (MB): leave as is (128)
Timeout: 1 min

Okay now hit [ Create function ].

Add trigger for "alertmanager_alerts" DynamoDB table

Go to Triggers > Add > DynamoDB:

Table = alertmanager_alerts
Batch size = 1
Starting position = Trim horizon

Add trigger for "AlertManager-ingest" SNS topic

Go to Triggers > Add > SNS:

Topic = AlertManager-ingest

This topic allows the ingestor to receive alerts from Canary, CloudWatch & other SNS-compatible sources.