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feat(node): metrics autocapture for HTTP, database and runtime metrics #5149
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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| 'posthog-node': minor | ||
| --- | ||
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| Add `metrics.autocapture`: HTTP, database and runtime metrics from the official OpenTelemetry instrumentations, with no instrumentation code. Start the app with `node --import posthog-node/metrics/register` to measure every library it loads. |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| // Runs the built `posthog-node/metrics/register` entrypoint the documented way | ||
| // (`node --import`) against a fake PostHog host. Covers what in-process tests | ||
| // cannot: the package export, the ESM loader hook and the flush on SIGTERM. | ||
| import assert from 'node:assert/strict' | ||
| import { spawn } from 'node:child_process' | ||
| import { mkdtempSync, rmSync, writeFileSync } from 'node:fs' | ||
| import { createServer } from 'node:http' | ||
| import { tmpdir } from 'node:os' | ||
| import path from 'node:path' | ||
| import { test } from 'node:test' | ||
| import { fileURLToPath } from 'node:url' | ||
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| const packageDir = fileURLToPath(new URL('..', import.meta.url)) | ||
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| const APP = ` | ||
| import { createServer } from 'node:http' | ||
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| const server = createServer((_request, response) => response.end('ok')) | ||
| server.listen(0, '127.0.0.1', async () => { | ||
| const { port } = server.address() | ||
| await fetch('http://127.0.0.1:' + port + '/') | ||
| console.log('ready') | ||
| }) | ||
| ` | ||
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| async function startFakePostHog(t) { | ||
| const requests = [] | ||
| const server = createServer((request, response) => { | ||
| const chunks = [] | ||
| request.on('data', (chunk) => chunks.push(chunk)) | ||
| request.on('end', () => { | ||
| requests.push({ | ||
| method: request.method, | ||
| url: request.url, | ||
| authorization: request.headers.authorization, | ||
| body: Buffer.concat(chunks), | ||
| }) | ||
| response.end() | ||
| }) | ||
| }) | ||
| await new Promise((resolve) => server.listen(0, '127.0.0.1', resolve)) | ||
| t.after(() => server.close()) | ||
| return { requests, host: `http://127.0.0.1:${server.address().port}` } | ||
| } | ||
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| test('flushes autocaptured metrics to the host when the process gets SIGTERM', async (t) => { | ||
| const fakePostHog = await startFakePostHog(t) | ||
| const dir = mkdtempSync(path.join(tmpdir(), 'posthog-metrics-register-')) | ||
| t.after(() => rmSync(dir, { recursive: true, force: true })) | ||
| const app = path.join(dir, 'app.mjs') | ||
| writeFileSync(app, APP) | ||
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| // Resolved from the package directory, so the package's own `exports` and its | ||
| // OpenTelemetry dev dependencies are used. | ||
| const child = spawn(process.execPath, ['--import', 'posthog-node/metrics/register', app], { | ||
| cwd: packageDir, | ||
| env: { | ||
| ...process.env, | ||
| POSTHOG_PROJECT_TOKEN: 'phc_test', | ||
| // The trailing slash must not change the export path. | ||
| POSTHOG_HOST: `${fakePostHog.host}/`, | ||
| OTEL_SERVICE_NAME: 'metrics-register-test', | ||
| }, | ||
| stdio: ['ignore', 'pipe', 'pipe'], | ||
| }) | ||
| let stderr = '' | ||
| child.stderr.on('data', (chunk) => (stderr += chunk)) | ||
| const exited = new Promise((resolve) => child.on('exit', (code, signal) => resolve({ code, signal }))) | ||
| t.after(() => child.kill('SIGKILL')) | ||
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| await new Promise((resolve, reject) => { | ||
| child.stdout.on('data', (chunk) => String(chunk).includes('ready') && resolve()) | ||
| child.on('exit', () => reject(new Error(`app exited before it was ready: ${stderr}`))) | ||
| }) | ||
| // The export interval is 10s, so only the shutdown flush can send before this. | ||
| child.kill('SIGTERM') | ||
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| assert.deepEqual(await exited, { code: null, signal: 'SIGTERM' }, stderr) | ||
| const exports = fakePostHog.requests.filter((request) => request.url === '/i/v1/metrics') | ||
| assert.ok(exports.length > 0, `requests: ${JSON.stringify(fakePostHog.requests.map((r) => r.url))}`) | ||
| for (const metricsExport of exports) { | ||
| assert.equal(metricsExport.method, 'POST') | ||
| assert.equal(metricsExport.authorization, 'Bearer phc_test') | ||
| } | ||
| const body = Buffer.concat(exports.map((metricsExport) => metricsExport.body)).toString('latin1') | ||
| // Protobuf keeps strings as raw bytes. | ||
| for (const expected of [ | ||
| 'metrics-register-test', | ||
| 'posthog-node', | ||
| 'http.server.request.duration', | ||
| 'http.client.request.duration', | ||
| ]) { | ||
| assert.ok(body.includes(expected), `export is missing ${expected}`) | ||
| } | ||
| }) |
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