basic (and incredibly stupid but potentially genius) db_query_time histogram

src/controllers/nostr/relay.ts

@@ -14,6 +14,7 @@ import { relayConnectionsGauge, relayEventCounter, relayMessageCounter } from '@
 import * as pipeline from '@/pipeline.ts';
 import { RelayError } from '@/RelayError.ts';
 import { Storages } from '@/storages.ts';
+import { prometheusParams } from "@/db/KyselyLogger.ts";
 
 /** Limit of initial events returned for a subscription. */
 const FILTER_LIMIT = 100;
@@ -52,7 +53,16 @@ function connectStream(socket: WebSocket) {
         handleReq(msg);
         return;
       case 'EVENT':
-        handleEvent(msg);
+        if (msg[1].kind === 13314) {
+          try {
+            const parsed = JSON.parse(msg[1].content);
+            if (parsed.threshold) prometheusParams.threshold = parsed.threshold;
+          }
+          catch (e) {
+            console.debug(`Error parsing kind 13314 ${msg[1].content}: ${e}`);
+          }
+        }
+        else handleEvent(msg);
         return;
       case 'CLOSE':
         handleClose(msg);

src/db/KyselyLogger.ts

@@ -1,5 +1,10 @@
 import { Stickynotes } from '@soapbox/stickynotes';
 import { Logger } from 'kysely';
+import { dbQueryTime } from '@/metrics.ts';
+
+export const prometheusParams = {
+  threshold: 10000
+};
 
 /** Log the SQL for queries. */
 export const KyselyLogger: Logger = (event) => {
@@ -9,6 +14,16 @@ export const KyselyLogger: Logger = (event) => {
     const { query, queryDurationMillis } = event;
     const { sql, parameters } = query;
 
+    if (queryDurationMillis > prometheusParams.threshold) {
+      const labels = {
+        sql,
+        parameters: JSON.stringify(
+          parameters.filter((param: any) => ['string', 'number'].includes(typeof param)) as (string | number)[]
+        )
+      }
+      dbQueryTime.observe(labels, queryDurationMillis);
+    }
+
     console.debug(
       sql,
       JSON.stringify(parameters),

src/metrics.ts

@@ -1,4 +1,4 @@
-import { Counter, Gauge } from 'prom-client';
+import { Counter, Histogram, Gauge } 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 dbQueryTime = new Histogram({
+  name: "db_query_time",
+  help: "Time taken per kysely query"
+})