Feature/ccm 17116 metrics

[nhsd-angel-pastor]

Description

To summarise, the changes are:

• Updated the event publisher in typescript and in python to record the events published as a metric (see Confluence for the list of metrics )

• As the event publisher now publishes metrics, it needs the dimension environment, so adding in the configuration of all the lambdas the environment name
  -- Lifted the metric-handler from comms-mgr

• Consolidated existing metrics namespaces into the DL metrics namespace
  left as an environment variable the DL_METRICS_NAMESPACE in case we want to have a different namespace, e.g. Digital Letters/MESH, Digital Letters/PDM

• Kept as it was the existing metrics with configurable name.

See comment for the tests evidences.

Context

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.

[nhsd-angel-pastor]

Signature taken from https://github.com/NHSDigital/mesh-client/blob/3.2.3/mesh_client/__init__.py#L512

[nhsd-angel-pastor]

using list_messages method instead of iterate_all_messages because as per documentation the iterate is slower (see https://github.com/NHSDigital/mesh-client/blob/3.2.3/mesh_client/__init__.py#L839)

[Ian-Hodges]

The docstring should be on the first line after the function declaration

Suggested change

	def record(self, value, **kwargs):
	metric_name = kwargs.get('name', self.name)
	"""
	method for reporting metric
	"""
	def record(self, value, **kwargs):
	"""
	method for reporting metric
	"""
	metric_name = kwargs.get('name', self.name)

[Ian-Hodges]

I don't think the new "name override" logic has been covered in the unit tests.

[Ian-Hodges]

This seems a bit smelly to me. Mainly the hardcoding of the event name. Not sure if we need/want to change it now, but an option would be to pass in a metricName function.

Suggested change

	let key = event.type;
	if (event.type === PRINT_LETTER_TRANSITIONED_EVENT_TYPE) {
	const status = (event as Record<string, any>).data?.status as
	| string
	| undefined;
	if (status) key = `${event.type}_${status}`;
	}
	const key = this.config.metricKeyResolver?.(event) ?? event.type;

The updated method signature:

export interface EventPublisherDependencies {
  eventBusArn: string;
  dlqUrl: string;
  logger: Logger;
  sqsClient: SQSClient;
  eventBridgeClient: EventBridgeClient;
  metricHandler: MetricHandler;
  metricKeyResolver?: (event: PublishableEvent) => string;
}

/root/repos/nhs-notify-digital-letters/lambdas/print-status-handler/src/container.ts:

  const eventPublisher = new EventPublisher({
    eventBusArn: eventPublisherEventBusArn,
    dlqUrl: eventPublisherDlqUrl,
    logger,
    sqsClient,
    eventBridgeClient,
    metricHandler: new MetricHandler(dlMetricsNamespace, [
      { Name: 'Environment', Value: environment },
    ]),
    metricKeyResolver: (event) => {
      const status = (event as Record<string, unknown>).data &&
        ((event as Record<string, unknown>).data as Record<string, unknown>).status as string | undefined;
      return status ? `${event.type}_${status}` : event.type;
    },
  });