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feat(prometheus): add getMetricsRequestHandler-method to Prometheus #1879

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merged 11 commits into from
Feb 8, 2021
Merged

feat(prometheus): add getMetricsRequestHandler-method to Prometheus #1879

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c881208
feat(prometheus): add `getMetricsRequestHandler`-method to Prometheus…
tapico-weyert Jan 27, 2021
d4dbd22
Merge branch 'main' into expose-request-handler
weyert Jan 28, 2021
23c1f77
test(prometheus): add sinon to write unit test
tapico-weyert Jan 28, 2021
57715c7
style(prometheus): fix the linting issue
tapico-weyert Jan 28, 2021
2233775
Merge branch 'main' into expose-request-handler
vmarchaud Feb 1, 2021
e81465c
Merge branch 'main' into expose-request-handler
weyert Feb 2, 2021
548a7e3
Merge branch 'main' into expose-request-handler
weyert Feb 3, 2021
c1468ff
chore: regenerated package-lock.json file
tapico-weyert Feb 3, 2021
f67d72f
chore: merge main branch into feature branch
tapico-weyert Feb 7, 2021
5392643
fix: remove `package-lock.json` file from `exporter-prometheus`-package
tapico-weyert Feb 7, 2021
141c21c
chore: revert the deletion of `package-lock.json` in root
tapico-weyert Feb 8, 2021
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2 changes: 2 additions & 0 deletions packages/opentelemetry-exporter-prometheus/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -41,11 +41,13 @@
"devDependencies": {
"@types/mocha": "8.2.0",
"@types/node": "14.14.20",
"@types/sinon": "9.0.10",
"codecov": "3.8.1",
"gts": "2.0.2",
"mocha": "7.2.0",
"nyc": "15.1.0",
"rimraf": "3.0.2",
"sinon": "9.2.3",
"ts-mocha": "8.0.0",
"ts-node": "9.1.1",
"typescript": "3.9.7"
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12 changes: 12 additions & 0 deletions packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts
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Expand Up @@ -157,6 +157,18 @@ export class PrometheusExporter implements MetricExporter {
});
}

/**
* Request handler that responds with the current state of metrics
* @param request Incoming HTTP request of server instance
* @param response HTTP response objet used to response to request
*/
public getMetricsRequestHandler(
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This function names implies you are getting a handler, which is not the what is actually happening. I think it would be smarter to return a middleware that is compatible with express and other web frameworks:

public getMetricsRequestHandler() {
  const self = this;
  return function metricsHandler(req, res, next) {
	// req validation?
    // suppress instrumenting this method? optionally?
	// error handling?	

    self.exportMetrics(res);
  };
}

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@weyert weyert Jan 29, 2021 •
edited
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The idea I was having to return a raw handler which has the IncomingMessage, and ServerResponse arguments as we can't really be sure what the user's framework is. I was thinking the user could do something like this for Express:

app.get('/metrics', (req, res) => {
    return exporter.getMetricsRequestHandler(req, res)
})

while for Hapi you could do something like:

function HapiWrapper(exporter) {
    const handler = exporter.getMetricsRequestHandler()
    return async ( { raw }, h) {
         await handler(raw.req, raw.res)
         return h.close
    } 
}

while for Koa something like:

const router = app.router()
router.get('/metrics', async (ctx) => {
   await handle(ctx.req, ctx.res)
   ctx.respond = false
})

Probably would need to allow the handler to be async but the above the idea to offer most flexibility. Maybe the name needs to better reflect this?

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But you have a point maybe it should be returned with .bind(this)

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I agree with @weyert here, its better to use a simpler model that doesn't necessarely match express api so it can be used with every framework (at the cost of having a different usage)

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Thank you @vmarchaud :)

_request: IncomingMessage,
response: ServerResponse
) {
this._exportMetrics(response);
}

/**
* Request handler used by http library to respond to incoming requests
* for the current state of metrics by the Prometheus backend.
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19 changes: 19 additions & 0 deletions packages/opentelemetry-exporter-prometheus/test/PrometheusExporter.test.ts
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Expand Up @@ -24,9 +24,11 @@ import {
HistogramAggregator,
} from '@opentelemetry/metrics';
import * as assert from 'assert';
import * as sinon from 'sinon';
import * as http from 'http';
import { PrometheusExporter } from '../src';
import { mockAggregator, mockedHrTimeMs } from './util';
import { SinonStubbedInstance } from 'sinon';

describe('PrometheusExporter', () => {
mockAggregator(SumAggregator);
Expand Down Expand Up @@ -171,6 +173,23 @@ describe('PrometheusExporter', () => {
return done();
});
});

it('should able to call getMetricsRequestHandler function to generate response with metrics', () => {
const exporter = new PrometheusExporter({ preventServerStart: true });
const mockRequest: SinonStubbedInstance<http.IncomingMessage> = sinon.createStubInstance(
http.IncomingMessage
);
const mockResponse: SinonStubbedInstance<http.ServerResponse> = sinon.createStubInstance(
http.ServerResponse
);
exporter.getMetricsRequestHandler(
(mockRequest as unknown) as http.IncomingMessage,
(mockResponse as unknown) as http.ServerResponse
);
sinon.assert.calledOnce(mockResponse.setHeader);
sinon.assert.calledOnce(mockResponse.end);
assert.strictEqual(mockResponse.statusCode, 200);
});
});

describe('export', () => {
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