[server] added metric for db pool queueing (#18477) (#18481)

Author: svenefftinge

components/server/src/init.ts

@@ -57,7 +57,7 @@ import { Server } from "./server";
 import { log, LogrusLogLevel } from "@gitpod/gitpod-protocol/lib/util/logging";
 import { TracingManager } from "@gitpod/gitpod-protocol/lib/util/tracing";
 import { TypeORM } from "@gitpod/gitpod-db/lib";
-import { dbConnectionsFree, dbConnectionsTotal } from "./prometheus-metrics";
+import { dbConnectionsEnqueued, dbConnectionsFree, dbConnectionsTotal } from "./prometheus-metrics";
 if (process.env.NODE_ENV === "development") {
     require("longjohn");
 }
@@ -85,6 +85,10 @@ export async function start(container: Container) {
             const activeConnections = pool._allConnections.length;
             const freeConnections = pool._freeConnections.length;
 
+            pool.on("enqueue", function () {
+                dbConnectionsEnqueued.inc();
+            });
+
             dbConnectionsTotal.set(activeConnections);
             dbConnectionsFree.set(freeConnections);
         } catch (error) {

components/server/src/prometheus-metrics.ts

@@ -47,6 +47,11 @@ export const dbConnectionsFree = new prometheusClient.Gauge({
     help: "Number of free connections in TypeORM pool",
 });
 
+export const dbConnectionsEnqueued = new prometheusClient.Counter({
+    name: "gitpod_typeorm_enqueued_connections",
+    help: "Number of times requests put on the queue, because the pool was maxed out.",
+});
+
 const loginCompletedTotal = new prometheusClient.Counter({
     name: "gitpod_login_completed_total",
     help: "Total number of logins completed into gitpod, by status",