feat: added metrics

.gitignore

@@ -105,3 +105,5 @@ dist
 
 # reports of jest tests
 reports
+
+src/version.ts

README.md

@@ -114,6 +114,11 @@ This package allows you to configure various options for loading and managing co
 - **Default**: `./config`
 - **Description**: The path to the local configuration folder.
 
+### `metricsRegistry`
+- **Type**: `promClient.Registry`
+- **Optional**: `true`
+- **Description**: The prometheus registry to use for metrics. If not provided, metrics are not provided.
+
 ## Environment Variable Configuration
 
 The following environment variables can be used to configure the options:
@@ -243,6 +248,11 @@ try {
   ```
 - **Description**: This error occurs when there is a version mismatch between the remote and local schemas. The payload includes the versions of both the remote and local schemas.
 
+### `promClientNotInstalledError`
+- **Code**: `8`
+- **Payload**: `Error`
+- **Description**: This error occurs when the `prom-client` package is not installed. The payload contains the error object.
+
 # Debugging
 If for some reason you want to debug the package you can either use the `getConfigParts` or the `getResolvedOptions` functions described in the API or use the more powerful debug logger.
 

package.json

@@ -16,12 +16,14 @@
     "prelint": "npm run format",
     "lint": "eslint .",
     "lint:fix": "eslint --fix .",
+    "pretest": "npm run generate:version",
     "test": "cross-env SUPPRESS_NO_CONFIG_WARNING=true NODE_CONFIG_STRICT_MODE=false jest --config=./tests/configurations/jest.config.js",
-    "prebuild": "npm run clean",
+    "prebuild": "npm run clean && npm run generate:version",
     "build": "tsc --project tsconfig.build.json",
     "start": "npm run build && cd dist && node ./index.js",
     "clean": "rimraf dist",
-    "prepublish": "npm run build"
+    "prepublish": "npm run build",
+    "generate:version": "node scripts/generateVersionFile.mjs"
   },
   "repository": {
     "type": "git",
@@ -61,7 +63,13 @@
     "undici": "^6.18.2"
   },
   "peerDependencies": {
-    "@map-colonies/schemas": "^1.0.0"
+    "@map-colonies/schemas": "^1.0.0",
+    "prom-client": "^15.0.0"
+  },
+  "peerDependenciesMeta": {
+    "prom-client": {
+      "optional": true
+    }
   },
   "devDependencies": {
     "@commitlint/cli": "^11.0.0",
@@ -80,6 +88,7 @@
     "prettier": "^2.2.1",
     "pretty-quick": "^3.1.0",
     "ts-jest": "^29.1.5",
-    "typescript": "^5.4.5"
+    "typescript": "^5.4.5",
+    "prom-client": "^15.0.0"
   }
 }

scripts/generateVersionFile.mjs

@@ -0,0 +1,10 @@
+import { writeFileSync } from 'fs';
+import { readPackageJsonSync } from '@map-colonies/read-pkg';
+
+const packageJson = readPackageJsonSync();
+const version = packageJson.version;
+const versionFile = 'src/version.ts';
+
+const content = `/* prettier-ignore */\n/* eslint-disable*/\nexport const PACKAGE_VERSION = '${version}';\n`;
+
+writeFileSync(versionFile, content);

src/config.ts

@@ -4,14 +4,15 @@ import configPkg from 'config';
 import semver from 'semver';
 import lodash, { type GetFieldType } from 'lodash';
 import { getEnvValues } from './env';
-import { BaseOptions, ConfigOptions, ConfigInstance } from './types';
+import { BaseOptions, ConfigOptions, ConfigInstance, Config } from './types';
 import { loadSchema } from './schemas';
 import { getOptions, initializeOptions } from './options';
 import { getRemoteConfig, getServerCapabilities } from './httpClient';
 import { ajvConfigValidator, validate } from './validator';
 import { createDebug } from './utils/debug';
 import { LOCAL_SCHEMAS_PACKAGE_VERSION } from './constants';
 import { createConfigError } from './errors';
+import { initializeMetrics } from './metrics';
 
 const debug = createDebug('config');
 
@@ -30,11 +31,12 @@ export async function config<T extends { [typeSymbol]: unknown; $id: string }>(
 ): Promise<ConfigInstance<T[typeof typeSymbol]>> {
   // handle package options
   debug('config called with options: %j', { ...options, schema: options.schema.$id });
-  const { schema: baseSchema, ...unvalidatedOptions } = options;
+  const { schema: baseSchema, metricsRegistry, ...unvalidatedOptions } = options;
   const { configName, offlineMode, version, ignoreServerIsOlderVersionError } = initializeOptions(unvalidatedOptions);
 
   let remoteConfig: object | T = {};
 
+  let serverConfigResponse: Config | undefined = undefined;
   // handle remote config
   if (offlineMode !== true) {
     debug('handling fetching remote data');
@@ -58,7 +60,7 @@ export async function config<T extends { [typeSymbol]: unknown; $id: string }>(
     }
 
     // get the remote config
-    const serverConfigResponse = await getRemoteConfig(configName, version);
+    serverConfigResponse = await getRemoteConfig(configName, version);
 
     if (serverConfigResponse.schemaId !== baseSchema.$id) {
       debug('schema version mismatch. local: %s, remote: %s', baseSchema.$id, serverConfigResponse.schemaId);
@@ -100,6 +102,10 @@ export async function config<T extends { [typeSymbol]: unknown; $id: string }>(
   // freeze the merged config so it can't be modified by the package user
   Object.freeze(validatedConfig);
 
+  if (metricsRegistry) {
+    initializeMetrics(metricsRegistry, baseSchema.$id, serverConfigResponse?.version);
+  }
+
   function get<TPath extends string>(path: TPath): GetFieldType<T[typeof typeSymbol], TPath> {
     debug('get called with path: %s', path);
     // eslint-disable-next-line @typescript-eslint/no-unsafe-return

src/errors.ts

@@ -9,6 +9,7 @@ const configErrors = {
   schemaNotFoundError: { code: 5, payload: {} as { schemaPath: string } },
   schemasPackageVersionMismatchError: { code: 6, payload: {} as { remotePackageVersion: string; localPackageVersion: string } },
   schemaVersionMismatchError: { code: 7, payload: {} as { remoteSchemaVersion: string; localSchemaVersion: string } },
+  promClientNotInstalledError: { code: 8, payload: {} as { message: string } },
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
 } as const satisfies Record<string, { code: number; payload: any }>;
 

src/metrics.ts

@@ -0,0 +1,59 @@
+import type { Registry } from 'prom-client';
+import { getOptions } from './options';
+import { PACKAGE_VERSION } from './version';
+import { LOCAL_SCHEMAS_PACKAGE_VERSION } from './constants';
+import { createDebug } from './utils/debug';
+import { createConfigError } from './errors';
+
+const debug = createDebug('metrics');
+const MILLISECONDS_PER_SECOND = 1000;
+
+let promClient: typeof import('prom-client') | undefined;
+
+function loadPromClient(): void {
+  if (promClient === undefined) {
+    debug('loading prom-client');
+    try {
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+      promClient = require('prom-client');
+    } catch (error) {
+      console.log('error', error);
+
+      throw createConfigError('promClientNotInstalledError', 'prom-client is not installed and metrics was initialized', error as Error);
+    }
+  }
+}
+
+export function initializeMetrics(registry: Registry, schemaId: string, actualVersion: number | undefined): void {
+  debug('initializing metrics');
+  loadPromClient();
+
+  if (promClient === undefined) {
+    return;
+  }
+
+  const { offlineMode, configName, version } = getOptions();
+  const gauge = new promClient.Gauge({
+    name: 'config_time_of_last_fetch_unix_timestamp',
+    help: 'The time of the last fetch of the configuration in unix timestamp',
+    labelNames: ['name', 'request_version', 'actual_version', 'offline_mode', 'schemas_package_version', 'package_version', 'schema_id'],
+  });
+
+  /* eslint-disable @typescript-eslint/naming-convention */
+  gauge.set(
+    {
+      name: configName,
+      request_version: version,
+      actual_version: actualVersion,
+      offline_mode: String(offlineMode ?? false),
+      schemas_package_version: LOCAL_SCHEMAS_PACKAGE_VERSION,
+      package_version: PACKAGE_VERSION,
+      schema_id: schemaId,
+    },
+
+    Date.now() / MILLISECONDS_PER_SECOND
+  );
+
+  /* eslint-enable @typescript-eslint/naming-convention */
+  registry.registerMetric(gauge);
+}

src/types.ts

@@ -1,5 +1,6 @@
 import { typeSymbol } from '@map-colonies/schemas/build/schemas/symbol';
 import { JSONSchemaType } from 'ajv';
+import type { Registry } from 'prom-client';
 
 type Prettify<T> = {
   [K in keyof T]: T[K];
@@ -77,6 +78,11 @@ export type ConfigOptions<T extends SchemaWithType> = Prettify<
      * The schema of the configuration object.
      */
     schema: T;
+    /**
+     * The registry for the metrics. If not provided, the metrics will not be registered.
+     * Depends on the prom-client package being installed.
+     */
+    metricsRegistry?: Registry;
   }
 >;
 

tests/metrics.spec.ts

@@ -0,0 +1,40 @@
+import { Registry } from 'prom-client';
+import { getOptions } from '../src/options';
+import { BaseOptions } from '../src/types';
+import { initializeMetrics } from '../src/metrics';
+import { PACKAGE_VERSION } from '../src/version';
+import { LOCAL_SCHEMAS_PACKAGE_VERSION } from '../src/constants';
+
+jest.mock('../src/options');
+
+const mockedGetOptions = getOptions as jest.MockedFunction<typeof getOptions>;
+
+mockedGetOptions.mockReturnValue({
+  offlineMode: false,
+  configName: 'avi',
+  version: 1,
+} as BaseOptions);
+
+describe('httpClient', () => {
+  beforeEach(() => {});
+
+  describe('#initializeMetrics', () => {
+    it('should initialize the metrics in the registry with the correct labels', async () => {
+      const registry = new Registry();
+      initializeMetrics(registry, 'schema', 1);
+
+      const metric = (await registry.getMetricsAsJSON())[0];
+      expect(metric).toHaveProperty('name', 'config_time_of_last_fetch_unix_timestamp');
+      expect(metric).toHaveProperty('values[0].labels', {
+        /* eslint-disable @typescript-eslint/naming-convention */
+        actual_version: 1,
+        name: 'avi',
+        offline_mode: 'false',
+        package_version: PACKAGE_VERSION,
+        request_version: 1,
+        schema_id: 'schema',
+        schemas_package_version: LOCAL_SCHEMAS_PACKAGE_VERSION,
+      });
+    });
+  });
+});