Merge branch 'db-query-time-prom-metric' into 'main'

basic (and incredibly stupid but potentially genius) db_query_time histogram

See merge request soapbox-pub/ditto!400

src/db/KyselyLogger.ts

@@ -1,5 +1,6 @@
 import { Stickynotes } from '@soapbox/stickynotes';
 import { Logger } from 'kysely';
+import { dbQueryTimeHistogram } from '@/metrics.ts';
 
 /** Log the SQL for queries. */
 export const KyselyLogger: Logger = (event) => {
@@ -9,6 +10,8 @@ export const KyselyLogger: Logger = (event) => {
     const { query, queryDurationMillis } = event;
     const { sql, parameters } = query;
 
+    dbQueryTimeHistogram.observe(queryDurationMillis);
+
     console.debug(
       sql,
       JSON.stringify(parameters),

src/metrics.ts

@@ -1,4 +1,4 @@
-import { Counter, Gauge } from 'prom-client';
+import { Counter, Gauge, Histogram } from 'prom-client';
 
 export const httpRequestCounter = new Counter({
   name: 'http_requests_total',
@@ -67,3 +67,8 @@ export const dbAvailableConnectionsGauge = new Gauge({
   name: 'db_available_connections',
   help: 'Number of available connections in the database pool',
 });
+
+export const dbQueryTimeHistogram = new Histogram({
+  name: 'db_query_duration_seconds',
+  help: 'Duration of database queries',
+});