Feat: Add Prometheus metrics

CHANGELOG.md

@@ -5,6 +5,39 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [CalVer](https://calver.org/).
 
+## [unreleased]
+
+### Added
+- It is now possible to expose prometheus metrics from vidi. To enable metrics on the `/metrics`-endpoint, enable it in `config.js`. note that the default port is `9100`.
+  ```json
+  "metrics": {
+    "enabled": true,
+  },
+  ```
+- Currently the metrics consists of:
+
+  1. Print Controller (print.js)
+  - `vidi_controllers_print_print_requests_total` (Counter): Counts the total number of print requests processed. Labels: scale, format, status, template, db. Helps track print request volume.
+  - `vidi_controllers_print_duration_milliseconds` (Histogram): Measures the duration of print operations in milliseconds. Labels: format, template, db, scale. Buckets: 100, 500, 1000, 2000, 5000, 10000, 30000, 60000, 120000, 240000 milliseconds.
+
+  2. WMS Controller (wms.js)
+  - `vidi_controllers_gc2_wms_requests_total` (Counter): Counts the total number of WMS requests processed. Labels: db, request_type, status.
+  - `vidi_controllers_gc2_wms_request_duration_milliseconds` (Histogram): Measures the duration of WMS requests in milliseconds. Labels: db, request_type. Buckets: 100, 500, 1000, 2000, 5000, 10000, 30000, 60000, 120000, 240000 milliseconds.
+  - `vidi_controllers_gc2_wms_response_size_bytes` (Histogram): Measures the size of WMS responses in bytes. Labels: db, request_type. Buckets: 1000, 10000, 100000, 1000000, 10000000, 100000000 bytes.
+
+  3. SQL Controller (sql.js)
+  - `vidi_controllers_gc2_sql_queries_total` (Counter): Counts the total number of SQL queries processed. Labels: db, format, status.
+  - `vidi_controllers_gc2_sql_query_duration_milliseconds` (Histogram): Measures the duration of SQL queries in milliseconds. Labels: db, format. Buckets: 100, 500, 1000, 2000, 5000, 10000, 30000, 60000, 120000, 240000 milliseconds.
+  - `vidi_controllers_gc2_sql_response_size_bytes` (Histogram): Measures the size of SQL query responses in bytes. Labels: db, format. Buckets: 1000, 10000, 100000, 1000000, 10000000, 100000000 bytes.
+
+  4. Express server
+  - `vidi_http_request` (Histogram): Measures the duration of HTTP-endpoints in seconds. Labels: status_code, method, path. Buckets: 0.003, 0.03, 0.1, 0.3, 1.5, 10 seconds.
+
+  5. Error Monitoring
+  - `vidi_uncaught_exceptions_total` (Counter): Counts uncaught exceptions and unhandled promise rejections. Labels: type, origin. Helps track application stability.
+  - `vidi_socket_errors_total` (Counter): Counts socket.io connection and server errors. Labels: event, namespace. Helps monitor real-time communication issues.
+
+
 ## [2025.6.2] - 2025-19-6
 
 ### Added

controllers/gc2/sql.js

@@ -7,10 +7,23 @@
 var express = require('express');
 var router = express.Router();
 var config = require('../../config/config.js').gc2;
+var metrics = require('../../modules/metrics');
 var request = require('request');
 var fs = require('fs');
 
 var query = function (req, response) {
+    // Get SQL metrics if enabled
+    const sqlMetrics = metrics.isEnabled() ? metrics.getSqlMetrics() : null;
+
+    // Start timing the query
+    let startTime;
+    if (sqlMetrics) {
+        startTime = Date.now();
+    }
+
+    // Track response size
+    let responseSize = 0;
+
     req.setTimeout(0); // no timeout
     var db = req.params.db,
         q = req.body.q || req.query.q,
@@ -89,16 +102,36 @@ var query = function (req, response) {
         if (!store) {
             response.writeHead(res.statusCode, headers);
         }
+
+        // Track query status in the counter
+        if (sqlMetrics) {
+            sqlMetrics.counter.inc({
+                db: db,
+                format: format,
+                status: res.statusCode >= 400 ? 'error' : 'success'
+            });
+        }
     });
 
     rem.on('data', function (chunk) {
+        responseSize += chunk.length;
         if (store) {
             writeStream.write(chunk, 'binary');
         } else {
             response.write(chunk);
         }
     });
+
     rem.on('end', function () {
+        // End timer and record duration with labels
+        if (sqlMetrics) {
+            const durationMs = Date.now() - startTime;
+            sqlMetrics.duration.observe({ db: db, format: format }, durationMs);
+
+            // Record response size
+            sqlMetrics.responseSize.observe({ db: db, format: format }, responseSize);
+        }
+
         if (store) {
             console.log("Result saved");
             response.send({"success": true, "file": fileName});

controllers/gc2/wms.js

@@ -7,9 +7,29 @@
 const express = require('express');
 const router = express.Router();
 const config = require('../../config/config.js').gc2;
+const metrics = require('../../modules/metrics');
 const request = require('request');
 
 const proxifyRequest = (req, response) => {
+    // Get WMS metrics if enabled
+    const wmsMetrics = metrics.isEnabled() ? metrics.getWmsMetrics() : null;
+
+    // Start timing the request
+    let startTime;
+    if (wmsMetrics) {
+        startTime = Date.now();
+    }
+
+    // Track response size
+    let responseSize = 0;
+
+    // Determine request type (WMS, mapcache, gmaps)
+    const requestType = req.url.includes('/mapcache/') ? 
+        (req.url.includes('/gmaps/') ? 'gmaps' : 'mapcache') : 'wms';
+
+    // Get db from params
+    const db = req.params.db;
+
     let requestURL = config.host + encodeURI(decodeURIComponent(req.url.substr(4)));
 
     // Rewrite URL in case of subUser
@@ -26,7 +46,35 @@ const proxifyRequest = (req, response) => {
         options.headers = {Cookie: "PHPSESSID=" + req.session.gc2SessionId + ";"}
     }
 
-    request(options).pipe(response);
+    const wmsRequest = request(options);
+
+    wmsRequest.on('response', function(res) {
+        // Track request status in the counter
+        if (wmsMetrics) {
+            wmsMetrics.counter.inc({
+                db: db,
+                request_type: requestType,
+                status: res.statusCode >= 400 ? 'error' : 'success'
+            });
+        }
+    });
+
+    wmsRequest.on('data', function(chunk) {
+        responseSize += chunk.length;
+    });
+
+    wmsRequest.on('end', function() {
+        // End timer and record duration with labels
+        if (wmsMetrics) {
+            const durationMs = Date.now() - startTime;
+            wmsMetrics.duration.observe({ db: db, request_type: requestType }, durationMs);
+
+            // Record response size
+            wmsMetrics.responseSize.observe({ db: db, request_type: requestType }, responseSize);
+        }
+    });
+
+    wmsRequest.pipe(response);
 };
 
 router.all('/api/wms/:db/:schema', proxifyRequest);