feat: add way to inject custom prom-client instance (#100)

SkeLLLa · Jan 14, 2024 · aa873d8 · aa873d8
1 parent 8d62106
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Showing 6 changed files with 47 additions and 7 deletions.
diff --git a/README.md b/README.md
@@ -133,6 +133,8 @@ See for details [docs](docs/api/fastify-metrics.imetricspluginoptions.md)
 | [endpoint?](./docs/api/fastify-metrics.imetricspluginoptions.endpoint.md)             | string \| null \| [`Fastify.RouteOptions`](https://www.fastify.io/docs/api/latest/Reference/Routes/#routes-options) | `'/metrics'`        |
 | [name?](./docs/api/fastify-metrics.imetricspluginoptions.name.md)                     | string                                                                                                              | `'metrics'`         |
 | [routeMetrics?](./docs/api/fastify-metrics.imetricspluginoptions.routemetrics.md)     | [IRouteMetricsConfig](./docs/api/fastify-metrics.iroutemetricsconfig.md)                                            | `{ enabled: true }` |
+| [promClient?](./docs/api/fastify-metrics.imetricspluginoptions.promclient.md)         | `prom-client` instance \| null                                                                                                    | `null`              |
+
 
 #### Route metrics
 

diff --git a/docs/api/fastify-metrics.imetricspluginoptions.md b/docs/api/fastify-metrics.imetricspluginoptions.md
@@ -16,8 +16,9 @@ export interface IMetricsPluginOptions
 
 | Property                                                                              | Modifiers | Type                                                                | Description                                                                                                          |
 | ------------------------------------------------------------------------------------- | --------- | ------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------- |
-| [clearRegisterOnInit](./fastify-metrics.imetricspluginoptions.clearregisteroninit.md) |           | boolean                                                             | Clears the prom-client global registry before adding metrics. Default to <code>false</code>                          |
-| [defaultMetrics](./fastify-metrics.imetricspluginoptions.defaultmetrics.md)           |           | [IDefaultMetricsConfig](./fastify-metrics.idefaultmetricsconfig.md) | Default prom-client metrics config. Collect prometheus recommended and node.js specific metrics like event loop lag. |
-| [endpoint](./fastify-metrics.imetricspluginoptions.endpoint.md)                       |           | string \| null \| RouteOptions                                      | Endpoint to expose metrics in prometheus format. <code>null</code> - disables metrics exposure                       |
-| [name](./fastify-metrics.imetricspluginoptions.name.md)                               |           | string                                                              | Plugin name that will be registered in fastify instance.                                                             |
-| [routeMetrics](./fastify-metrics.imetricspluginoptions.routemetrics.md)               |           | [IRouteMetricsConfig](./fastify-metrics.iroutemetricsconfig.md)     | Per route metrics config. Collect response time metric on requests                                                   |
+| [clearRegisterOnInit](./fastify-metrics.imetricspluginoptions.clearregisteroninit.md) |           | boolean                                                             | Clears the prom-client global registry before adding metrics. Defaults to <code>false</code>.                        |
+| [defaultMetrics](./fastify-metrics.imetricspluginoptions.defaultmetrics.md)           |           | [IDefaultMetricsConfig](./fastify-metrics.idefaultmetricsconfig.md) | Default prom-client metrics config. Collects Prometheus recommended and Node.js specific metrics like event loop lag.|
+| [endpoint](./fastify-metrics.imetricspluginoptions.endpoint.md)                       |           | string \| null \| RouteOptions                                      | Endpoint to expose metrics in Prometheus format. <code>null</code> - disables metrics exposure.                      |
+| [name](./fastify-metrics.imetricspluginoptions.name.md)                               |           | string                                                              | Plugin name that will be registered in Fastify instance.                                                             |
+| [routeMetrics](./fastify-metrics.imetricspluginoptions.routemetrics.md)               |           | [IRouteMetricsConfig](./fastify-metrics.iroutemetricsconfig.md)     | Per route metrics config. Collects response time metric on requests.                                                  |
+| [promClient](./fastify-metrics.imetricspluginoptions.promclient.md)                   |           | `Client` \| null                                                    | Optional. Allows overriding the internally used Prometheus client instance. Defaults to `null`.                       |
diff --git a/src/__tests__/inject-prom-client.spec.ts b/src/__tests__/inject-prom-client.spec.ts
@@ -0,0 +1,27 @@
+import { afterEach, describe, expect, test } from '@jest/globals';
+import fastify from 'fastify';
+import type promClient from 'prom-client';
+import fastifyPlugin from '../';
+
+describe('metrics plugin', () => {
+  let app = fastify();
+
+  afterEach(async () => {
+    await app.close();
+  });
+
+  test('uses provided prom-client instance', async () => {
+    const testPromClient = {} as unknown as typeof promClient;
+
+    app = fastify();
+    await app.register(fastifyPlugin, {
+      promClient: testPromClient,
+      endpoint: '/metrics',
+      defaultMetrics: { enabled: false },
+      routeMetrics: { enabled: false },
+    });
+    await app.ready();
+
+    expect(app.metrics.client).toEqual(testPromClient);
+  });
+});
diff --git a/src/fastify-metrics.ts b/src/fastify-metrics.ts
@@ -46,6 +46,7 @@ export const DEFAULT_OPTIONS: IMetricsPluginOptions = {
   defaultMetrics: {
     enabled: true,
   },
+  promClient: null,
 };
 
 /**

diff --git a/src/index.ts b/src/index.ts
@@ -57,11 +57,13 @@ export default fastifyPlugin<Partial<IMetricsPluginOptions>>(
   async (fastify, options) => {
     const { name = 'metrics', clearRegisterOnInit = false } = options;
 
+    const promClient = options.promClient ?? client;
+
     if (clearRegisterOnInit) {
-      client.register.clear();
+      promClient.register.clear();
     }
 
-    const fm = new FastifyMetrics({ client, fastify, options });
+    const fm = new FastifyMetrics({ client: promClient, fastify, options });
     fastify.decorate<IFastifyMetrics>(name, fm);
   },
   {

diff --git a/src/types.ts b/src/types.ts
@@ -240,6 +240,13 @@ export interface IRouteMetricsConfig {
  * @public
  */
 export interface IMetricsPluginOptions {
+  /**
+   * PromClient instance to override default internal promClient
+   *
+   * @defaultValue promClient
+   */
+  promClient: typeof client | null;
+
   /**
    * Endpoint to expose metrics in prometheus format. `null` - disables metrics
    * exposure