feat(kpis): track total fingerprints used per model

Author: coderbyheart

kpis/totalFingerprintsUsed.spec.ts

@@ -0,0 +1,69 @@
+import {
+	DynamoDBClient,
+	type ScanInput,
+	type ScanOutput,
+} from '@aws-sdk/client-dynamodb'
+import assert from 'assert'
+import { describe, it, mock } from 'node:test'
+import { totalFingerprintsUsed } from './totalFingerprintsUsed.ts'
+
+await describe('totalFingerprintsUsed()', async () => {
+	await it('should return the total number of fingerprints used per model', async () => {
+		const send = mock.fn<(args: { input: ScanInput }) => Promise<ScanOutput>>(
+			async () => ({
+				Items: [
+					{
+						model: { S: 'model1' },
+						lastSeen: { S: '2023-01-01T12:34:56.000Z' },
+					},
+					{
+						model: { S: 'model1' },
+						lastSeen: { S: '2023-01-02T12:34:56.000Z' },
+					},
+					{
+						model: { S: 'model2' },
+						lastSeen: { S: '2023-01-01T12:34:56.000Z' },
+					},
+				],
+			}),
+		)
+		const db = new DynamoDBClient({})
+		db.send = send
+		const TableName = 'test-table'
+
+		const result = await totalFingerprintsUsed(db, TableName)()
+		assert.deepStrictEqual(
+			result,
+			new Map([
+				['model1', 2],
+				['model2', 1],
+			]),
+		)
+
+		assert.deepStrictEqual(send.mock.calls.length, 1)
+		assert.deepEqual(send.mock.calls[0]!.arguments[0].input, {
+			ExclusiveStartKey: undefined,
+			Limit: undefined,
+			TableName,
+			ExpressionAttributeNames: {
+				'#model': 'model',
+				'#lastSeen': 'lastSeen',
+			},
+			ProjectionExpression: '#model',
+			FilterExpression: 'attribute_exists(#lastSeen)',
+		})
+	})
+
+	await it('should return an empty map if no items are found', async () => {
+		const send = mock.fn<(args: { input: ScanInput }) => Promise<ScanOutput>>(
+			async () => ({}),
+		)
+		const db = new DynamoDBClient({})
+		db.send = send
+		const TableName = 'test-table'
+
+		const result = await totalFingerprintsUsed(db, TableName)()
+		assert.deepStrictEqual(result, new Map())
+		assert.equal(result.size, 0)
+	})
+})

kpis/totalFingerprintsUsed.ts

@@ -0,0 +1,29 @@
+import { type DynamoDBClient, paginateScan } from '@aws-sdk/client-dynamodb'
+import { unmarshall } from '@aws-sdk/util-dynamodb'
+
+/**
+ * Returns the total number of fingerprints used per model.
+ */
+export const totalFingerprintsUsed =
+	(db: DynamoDBClient, TableName: string) =>
+	async (): Promise<Map<string, number>> => {
+		const results = paginateScan(
+			{ client: db },
+			{
+				TableName,
+				ExpressionAttributeNames: {
+					'#model': 'model',
+					'#lastSeen': 'lastSeen',
+				},
+				ProjectionExpression: '#model',
+				FilterExpression: 'attribute_exists(#lastSeen)',
+			},
+		)
+		const countPerModel = new Map<string, number>()
+		for await (const { Items } of results) {
+			for (const item of (Items ?? []).map((i) => unmarshall(i))) {
+				countPerModel.set(item.model, (countPerModel.get(item.model) ?? 0) + 1)
+			}
+		}
+		return countPerModel
+	}

lambda/kpis.ts

@@ -14,6 +14,7 @@ import {
 import middy from '@middy/core'
 import { dailyActiveDevices } from '../kpis/dailyActiveDevices.ts'
 import { dailyActiveFingerprints } from '../kpis/dailyActiveFingerprints.ts'
+import { totalFingerprintsUsed } from '../kpis/totalFingerprintsUsed.ts'
 
 const { lastSeenTableName, devicesTableName, stackName } = fromEnv({
 	lastSeenTableName: 'LAST_SEEN_TABLE_NAME',
@@ -25,6 +26,7 @@ const ssm = new SSMClient({})
 const db = new DynamoDBClient({})
 const getDailyActiveDevices = dailyActiveDevices(db, lastSeenTableName)
 const getDailyActiveFingerprints = dailyActiveFingerprints(db, devicesTableName)
+const getTotalFingerprintsUsed = totalFingerprintsUsed(db, devicesTableName)
 
 const { track, metrics } = metricsForComponent('KPIs')
 
@@ -51,6 +53,12 @@ const h = async () => {
 				)
 			},
 		),
+		getTotalFingerprintsUsed().then((totalFingerprintsUsedPerModel) => {
+			console.log({ totalFingerprintsUsedPerModel })
+			for (const [model, count] of totalFingerprintsUsedPerModel) {
+				track(`totalFingerprintsUsed:${model}`, MetricUnit.Count, count)
+			}
+		}),
 		// Current month's nRF Cloud costs
 		...(await getAllAccounts({ ssm, stackName })).map(async (account) => {
 			const settingsPromise =