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CloudWatch

In-memory CloudWatch implementation supporting metric data, alarms, and metric queries.

Supported Operations

Operation Description
PutMetricData Publish custom metric data points
GetMetricStatistics Query metric statistics over a time range
GetMetricData Query one or more metrics with math expressions
ListMetrics List available metrics with optional filters
PutMetricAlarm Create or update a metric alarm
DescribeAlarms Get alarm details and state
DeleteAlarms Delete one or more alarms
ListTagsForResource List tags on an alarm
TagResource Add tags to an alarm
UntagResource Remove tags from an alarm

AWS CLI Examples

# Publish a custom metric
aws --endpoint-url http://localhost:8000 cloudwatch put-metric-data \
    --namespace MyApp \
    --metric-name RequestCount \
    --value 42 \
    --unit Count

# Query metric statistics
aws --endpoint-url http://localhost:8000 cloudwatch get-metric-statistics \
    --namespace MyApp \
    --metric-name RequestCount \
    --start-time 2024-01-01T00:00:00Z \
    --end-time 2024-01-02T00:00:00Z \
    --period 3600 \
    --statistics Sum

# Create an alarm
aws --endpoint-url http://localhost:8000 cloudwatch put-metric-alarm \
    --alarm-name HighErrorRate \
    --namespace MyApp \
    --metric-name ErrorCount \
    --threshold 100 \
    --comparison-operator GreaterThanThreshold \
    --evaluation-periods 1 \
    --period 300 \
    --statistic Sum

# Describe alarms
aws --endpoint-url http://localhost:8000 cloudwatch describe-alarms

# List metrics
aws --endpoint-url http://localhost:8000 cloudwatch list-metrics \
    --namespace MyApp

Known Limitations

  • Alarm state transitions do not trigger actions (SNS notifications, Auto Scaling, etc.).
  • Composite alarms are not supported.
  • Metric Insights queries in GetMetricData are not fully evaluated; basic SUM/AVG/MIN/MAX are supported.
  • CloudWatch dashboards, anomaly detection, and contributor insights are not implemented.
  • Metrics older than the in-memory retention window are not evicted automatically.