Merge branch 'pg-metrics' into 'main'

Collect database connections metrics

See merge request soapbox-pub/ditto!399

deno.json

@@ -50,7 +50,7 @@
     "iso-639-1": "npm:iso-639-1@2.1.15",
     "isomorphic-dompurify": "npm:isomorphic-dompurify@^2.11.0",
     "kysely": "npm:kysely@^0.27.3",
-    "kysely_deno_postgres": "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/f2948b86190a10faa293588775e162b3a8b52e70/mod.ts",
+    "kysely_deno_postgres": "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/b4725e74ad6ca359ba0e370b55dbb8bb845a8a83/mod.ts",
     "light-bolt11-decoder": "npm:light-bolt11-decoder",
     "linkify-plugin-hashtag": "npm:linkify-plugin-hashtag@^4.1.1",
     "linkify-string": "npm:linkify-string@^4.1.1",
@@ -59,6 +59,7 @@
     "nostr-relaypool": "npm:nostr-relaypool2@0.6.34",
     "nostr-tools": "npm:nostr-tools@2.5.1",
     "nostr-wasm": "npm:nostr-wasm@^0.1.0",
+    "postgres": "https://deno.land/x/postgres@v0.19.0/mod.ts",
     "prom-client": "npm:prom-client@^15.1.2",
     "question-deno": "https://raw.githubusercontent.com/ocpu/question-deno/10022b8e52555335aa510adb08b0a300df3cf904/mod.ts",
     "tldts": "npm:tldts@^6.0.14",

deno.lock

@@ -1391,6 +1391,10 @@
     "https://esm.sh/v135/kysely@0.17.1/denonext/dist/esm/index-nodeless.js": "6f73bbf2d73bc7e96cdabf941c4ae8c12f58fd7b441031edec44c029aed9532b",
     "https://gitlab.com/soapbox-pub/deno-safe-fetch/-/raw/v1.0.0/load.ts": "3f74ab08cf97d4a3e6994cb79422e9b0069495e017416858121d5ff8ae04ac2a",
     "https://gitlab.com/soapbox-pub/deno-safe-fetch/-/raw/v1.0.0/mod.ts": "5f505cd265aefbcb687cde6f98c79344d3292ee1dd978e85e5ffa84a617c6682",
+    "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/b4725e74ad6ca359ba0e370b55dbb8bb845a8a83/deps.ts": "b3dbecae69c30a5f161323b8c8ebd91d9af1eceb98fafab3091c7281a4b64fed",
+    "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/b4725e74ad6ca359ba0e370b55dbb8bb845a8a83/mod.ts": "662438fd3909984bb8cbaf3fd44d2121e949d11301baf21d6c3f057ccf9887de",
+    "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/b4725e74ad6ca359ba0e370b55dbb8bb845a8a83/src/PostgreSQLDriver.ts": "ea5a523bceeed420858b744beeb95d48976cb2b0d3f519a68b65a8229036cf6a",
+    "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/b4725e74ad6ca359ba0e370b55dbb8bb845a8a83/src/PostgreSQLDriverDatabaseConnection.ts": "11e2fc10a3abb3d0729613c4b7cdb9cb73b597fd77353311bb6707c73a635fc5",
     "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/f2948b86190a10faa293588775e162b3a8b52e70/deps.ts": "b3dbecae69c30a5f161323b8c8ebd91d9af1eceb98fafab3091c7281a4b64fed",
     "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/f2948b86190a10faa293588775e162b3a8b52e70/mod.ts": "662438fd3909984bb8cbaf3fd44d2121e949d11301baf21d6c3f057ccf9887de",
     "https://gitlab.com/soapbox-pub/kysely-deno-postgres/-/raw/f2948b86190a10faa293588775e162b3a8b52e70/src/PostgreSQLDriver.ts": "ac1a39e86fd676973bce215e19db1f26b82408b8f2bb09a3601802974ea7cec6",

src/controllers/metrics.ts

@@ -1,9 +1,15 @@
 import { register } from 'prom-client';
 
 import { AppController } from '@/app.ts';
+import { DittoDB } from '@/db/DittoDB.ts';
+import { dbAvailableConnectionsGauge, dbPoolSizeGauge } from '@/metrics.ts';
 
 /** Prometheus/OpenMetrics controller. */
 export const metricsController: AppController = async (c) => {
+  // Update some metrics at request time.
+  dbPoolSizeGauge.set(DittoDB.poolSize);
+  dbAvailableConnectionsGauge.set(DittoDB.availableConnections);
+
   const metrics = await register.metrics();
 
   const headers: HeadersInit = {

src/db/DittoDB.ts

@@ -37,6 +37,20 @@ export class DittoDB {
     return kysely;
   }
 
+  static get poolSize(): number {
+    if (Conf.db.dialect === 'postgres') {
+      return DittoPostgres.getPool().size;
+    }
+    return 1;
+  }
+
+  static get availableConnections(): number {
+    if (Conf.db.dialect === 'postgres') {
+      return DittoPostgres.getPool().available;
+    }
+    return 1;
+  }
+
   /** Migrate the database to the latest version. */
   static async migrate(kysely: Kysely<DittoTables>) {
     const migrator = new Migrator({

src/db/adapters/DittoPostgres.ts

@@ -1,5 +1,6 @@
 import { Kysely, PostgresAdapter, PostgresIntrospector, PostgresQueryCompiler } from 'kysely';
 import { PostgreSQLDriver } from 'kysely_deno_postgres';
+import { Pool } from 'postgres';
 
 import { Conf } from '@/config.ts';
 import { DittoTables } from '@/db/DittoTables.ts';
@@ -7,6 +8,14 @@ import { KyselyLogger } from '@/db/KyselyLogger.ts';
 
 export class DittoPostgres {
   static db: Kysely<DittoTables> | undefined;
+  static pool: Pool | undefined;
+
+  static getPool(): Pool {
+    if (!this.pool) {
+      this.pool = new Pool(Conf.databaseUrl, Conf.pg.poolSize);
+    }
+    return this.pool;
+  }
 
   // deno-lint-ignore require-await
   static async getInstance(): Promise<Kysely<DittoTables>> {
@@ -17,10 +26,7 @@ export class DittoPostgres {
             return new PostgresAdapter();
           },
           createDriver() {
-            return new PostgreSQLDriver(
-              { connectionString: Conf.databaseUrl },
-              Conf.pg.poolSize,
-            );
+            return new PostgreSQLDriver(DittoPostgres.getPool());
           },
           createIntrospector(db: Kysely<unknown>) {
             return new PostgresIntrospector(db);

src/metrics.ts

@@ -57,3 +57,13 @@ export const dbEventCounter = new Counter({
   help: 'Total number of database inserts',
   labelNames: ['kind'],
 });
+
+export const dbPoolSizeGauge = new Gauge({
+  name: 'db_pool_size',
+  help: 'Number of connections in the database pool',
+});
+
+export const dbAvailableConnectionsGauge = new Gauge({
+  name: 'db_available_connections',
+  help: 'Number of available connections in the database pool',
+});