CloudWatch Metrics and Alarms: Start metric streams from the CLI

Part 552 of AWS from Zero. This is lesson 11 in the CloudWatch Metrics and Alarms track.

What we are learning

Use start-metric-streams to start one explicit CloudWatch Metrics and Alarms operation and capture its response for follow-up checks. This lesson identifies the required input shape, saves the raw response, and keeps inspection separate from execution.

The AWS CLI operation is aws cloudwatch start-metric-streams. Required operation inputs: --names (list). The modeled top-level response contains no modeled response body.

Before you run it

aws sts get-caller-identity
REGION="${AWS_REGION:-ap-south-1}"
aws cloudwatch start-metric-streams help

Use a sandbox account or an approved learning environment. Read the operation help before supplying identifiers, ARNs, network ranges, policy documents, or customer data.

Cost note: Custom metrics, alarms, dashboards, API requests, and advanced features can incur charges.

The command

aws cloudwatch start-metric-streams \
  --generate-cli-skeleton input > part-552-request.json
 
# Edit every placeholder in part-552-request.json, then run:
aws cloudwatch start-metric-streams \
  --cli-input-json file://part-552-request.json \
  --region "$REGION" \
  --output json > part-552-response.json

The response is saved to part-552-response.json so inspection is separate from execution. Review part-552-request.json, replace every placeholder, and remove unsupported optional fields before the real call.

Inspect the result

# A zero-byte response can be normal for operations without a response body.
wc -c part-552-response.json
aws cloudwatch help

Compare the returned identifiers and status fields with the account, Region, and resource you intended to target. For asynchronous operations, continue with the service's matching get, list, or describe command until it reaches a terminal state.

One tiny variation

test -s part-552-response.json \
  && node -e "console.log(require('./part-552-response.json'))" \
  || echo "The operation returned no response document."

This variation changes output inspection rather than adding another infrastructure concept. Keep the raw JSON while developing a query so a narrow projection does not hide an error or unexpected field.

Common mistake

Do not treat a zero exit code as proof that the intended state is active everywhere. AWS control planes can be eventually consistent, and some operations start asynchronous work.

Cleanup

# This operation is read-only, operational, or needs resource-specific rollback.
# Re-read the command output before changing shared infrastructure.
rm -f part-552-request.json part-552-response.json part-552-payload.bin part-552-debug.log

Local request and response files may contain account IDs, ARNs, names, or service configuration. Remove them when the lab is complete and follow dependency-aware cleanup for any AWS resource you created.

Next, we will learn CloudWatch Metrics and Alarms: Tag resource from the CLI.

Official AWS CLI reference