CloudWatch

A Monitoring solution for AWS. Many AWS service send data to CloudWatch by default.

basic monitoring is free (reporting once per 5 minute period).
detailed monitoring can be enabled on EC2 to get reports every minute

CloudWatch Metrics

Every metric has a:

timestamp
namespace: metrics in different namespaces are isolated from each other
dimensions: a key-value pair for additional filtering

Custom Metrics

Allow applications to send their own metrics to CloudWatch. Supports a max rate of 1/second.

CloudWatch Dashboard

Customisable home pages where widgets can be used to visualise CloudWatch data.

Alternatively data can be pulled using the GetMetricData API and visualised with 3rd party tools.

CloudWatch Logs

Lambda can send logs as soon as it has the right IAMPolicy
Ec2 needs the right IAMPolicy and have a CloudWatch Agent installed.

Terminology

event: a record of activity with a timestamp and message
stream: a group of events that all belong to the same resource
groups: a group of streams that share the same retention and permission settings

Cloud Watch Alarms

Initiate actions based on CloudWatchMetrics.

State

OK: metric is within defined threshold
ALARM: metric outside defined threshold
INSUFFICIENT DATA: alarm just started, not enough data or not available

Action

When an alarm is triggered (transition state) an action can be taken

an EC2 action
a scaling action
an SNS notification