Module 2: Metrics

AWS CloudWatch is a monitoring and observability service that provides data and actionable insights for your applications. Key CloudWatch concepts include:

• Namespace: A container for metrics that share a common purpose or source
• Metric: A time-ordered set of data points representing values being measured
• Dimension: A name/value pair that uniquely identifies a metric
• Statistics: Aggregated data points for a specified period (sum, average, min, max, count)
• Period: The time interval over which statistics are applied
• Alarm: A resource that watches a single metric and performs actions based on the metric's value

Here's a basic example of creating a custom metric in Java using the AWS SDK:

// Create CloudWatch client
AmazonCloudWatch cloudWatch = AmazonCloudWatchClientBuilder.standard()
        .withRegion(Regions.US_WEST_2)
        .build();

// Define metric data
MetricDatum datum = new MetricDatum()
    .withMetricName("RequestLatency")
    .withUnit(StandardUnit.Milliseconds)
    .withValue(42.0)
    .withDimensions(new Dimension()
        .withName("ServiceName")
        .withValue("LoginService"));

// Create request and publish metric
PutMetricDataRequest request = new PutMetricDataRequest()
    .withNamespace("MyApplication")
    .withMetricData(datum);

PutMetricDataResult response = cloudWatch.putMetricData(request);

When implementing metrics, always consider:

• Using meaningful namespaces and dimensions for proper organization
• Selecting appropriate units for your measurements
• Emitting zeros for count metrics to enable accurate statistics calculation
• Choosing the appropriate aggregation period based on your monitoring needs

Percentiles are powerful statistics that help understand the distribution of your metric values:

• p50 (median): 50% of the data points are below this value
• p90: 90% of the data points are below this value
• p99: 99% of the data points are below this value

Percentiles are particularly useful for monitoring latency and response times, as they highlight the user experience better than averages.