/metrics doesn't show app's routes/controllers

[behrad]

I was expecting /metrics to show my strapi controllers/routes but I can't see my APIs stats inside.
Strapi version 3.5.3 (node v12.19.0)

[nboussarsaracn]

@wirehead simply installing the plugin and configuring it in config/middleware.js does not seem to work

@behrad do you have any news ? did you make it work somehow ?

[nboussarsaracn]

@behrad, I made it work but yes it does not appear in the controller routes - it just exposes /metrics route (assuming you did the configuration correctly)

[DanStockham]

The reason why that metrics are not being captured for prometheus is because everytime a request is invoked to an endpoint other than the /metrics endpoint, the context response object is always going to have 404 as it's status code.

{
  request: {
    method: 'GET',
    url: '/jobs',
    header: {
      host: 'localhost:1337',
      'user-agent': 'insomnia/2021.3.0',
      accept: '*/*'
    }
  },
  response: {
    status: 404,
    message: 'Not Found',
    header: [Object: null prototype] {
      vary: 'Origin',
      'strict-transport-security': 'max-age=31536000; includeSubDomains',
      'x-frame-options': 'SAMEORIGIN'
    }
  },
  app: { subdomainOffset: 2, proxy: false, env: 'development' },
  originalUrl: '/jobs',
  req: '<original node req>',
  res: '<original node res>',
  socket: '<original node socket>'
}

This is because the request-response cycle needs to complete so the response can be populated in the context

'use strict';

const apiMetrics = require('prometheus-api-metrics').koaMiddleware;
const HttpMetricsCollector = require('prometheus-api-metrics').HttpMetricsCollector;
HttpMetricsCollector.init();

module.exports = strapi => {

  return {
    initialize: function(cb) {
      const promSettings = strapi.config.middleware.settings.prom;
      const metricsPath = promSettings.metricsPath;
      const defaultMetricsInterval = promSettings.defaultMetricsInterval;
      const durationBuckets = promSettings.durationBuckets;
      const requestSizeBuckets = promSettings.requestSizeBuckets;
      const responseSizeBuckets = promSettings.responseSizeBuckets;
      const useUniqueHistogramName = promSettings.useUniqueHistogramName;
      const metricsPrefix = promSettings.metricsPrefix;
      const excludeRoutes = promSettings.excludeRoutes;
      const includeQueryParams = promSettings.includeQueryParams;

      const wrapped = apiMetrics({
        metricsPath,
        defaultMetricsInterval,
        durationBuckets,
        requestSizeBuckets,
        responseSizeBuckets,
        useUniqueHistogramName,
        metricsPrefix,
        excludeRoutes,
        includeQueryParams
      });

      strapi.app.use(async (ctx, next) => {
        await next(); //<-- this will move to controller action in the stack
        if (ctx.req.url === metricsPath) {
          return wrapped(ctx,next);
        } else if (ctx.req.url === `${metricsPath}.json`) {
          return wrapped(ctx,next);
        } else if ((ctx.response.status != 404)) {
          return wrapped(ctx,next);
        } else {
          return next();
        }
      });
    },
  };
};

In order for us to advance the request to the controller and then finally parse the correct reponse requires invoking the next keyword. This on the otherhand, will break the koaMiddleware as we're passing an already invoked next function.

Moving the middleware to the after configuration doesn't work and I haven't found a way to run the middleware after the controller has finished the request-response cycle

@wirehead Is there any way to can get around this?