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/*
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Express middleware for recording metrics about response time to requests.
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*/
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import { dirname } from "path";
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import { Router } from "express";
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import { get, new_histogram } from "@cocalc/server/metrics/metrics-recorder";
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import { join } from "path";
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import basePath from "@cocalc/backend/base-path";
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import getPool from "@cocalc/database/pool";
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import { getLogger } from "@cocalc/hub/logger";
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const log = getLogger("metrics");
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// initialize metrics
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const responseTimeHistogram = new_histogram("http_histogram", "http server", {
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  buckets: [0.01, 0.1, 1, 2, 5, 10, 20],
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  labels: ["path", "method", "code"],
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});
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// response time metrics
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function metrics(req, res, next) {
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  const resFinished = responseTimeHistogram.startTimer();
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  const originalEnd = res.end;
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  res.end = (...args) => {
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    originalEnd.apply(res, args);
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    if (!req.path) {
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      return;
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    }
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    // for regular paths, we ignore the file
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    const path = dirname(req.path).split("/").slice(0, 2).join("/");
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    resFinished({
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      path,
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      method: req.method,
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      code: res.statusCode,
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    });
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  };
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  next();
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}
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export function setupInstrumentation(router: Router) {
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  router.use(metrics);
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}
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async function isEnabled(pool): Promise<boolean> {
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  const { rows } = await pool.query(
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    "SELECT value FROM server_settings WHERE name='prometheus_metrics'",
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  );
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  const enabled = rows.length > 0 && rows[0].value == "yes";
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  log.info("isEnabled", enabled);
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  return enabled;
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}
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export function initMetricsEndpoint(router: Router) {
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  const endpoint = join(basePath, "metrics");
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  log.info("initMetricsEndpoint at ", endpoint);
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  // long cache so we can easily check before each response and it is still fast.
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  const pool = getPool("long");
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  router.get(endpoint, async (_req, res) => {
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    res.header("Content-Type", "text/plain");
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    res.header("Cache-Control", "no-cache, no-store");
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    if (!(await isEnabled(pool))) {
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      res.json({
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        error:
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          "Sharing of metrics at /metrics is disabled.  Metrics can be enabled in the site administration page.",
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      });
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      return;
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    }
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    const metricsRecorder = get();
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    if (metricsRecorder != null) {
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      res.send(await metricsRecorder.metrics());
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    } else {
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      res.json({ error: "Metrics recorder not initialized." });
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    }
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  });
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}
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