From d0b3b73fe4fc7ab930f5aa83ddcf26dd6f7aca46 Mon Sep 17 00:00:00 2001
From: devin ivy <devinivy@gmail.com>
Date: Wed, 16 Aug 2023 14:02:42 -0400
Subject: [PATCH] Handle db client errors on appview (#1481)

handle db client errors on bav
---
 packages/bsky/src/db/db.ts     |  4 ++++
 packages/bsky/tests/db.test.ts | 14 ++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/packages/bsky/src/db/db.ts b/packages/bsky/src/db/db.ts
index 7c984892ea1..51787023f20 100644
--- a/packages/bsky/src/db/db.ts
+++ b/packages/bsky/src/db/db.ts
@@ -3,6 +3,7 @@ import { Kysely, PostgresDialect } from 'kysely'
 import { Pool as PgPool, types as pgTypes } from 'pg'
 import DatabaseSchema, { DatabaseSchemaType } from './database-schema'
 import { PgOptions } from './types'
+import { dbLogger } from '../logger'
 
 export class Database {
   pool: PgPool
@@ -41,6 +42,7 @@ export class Database {
     }
 
     pool.on('connect', (client) => {
+      client.on('error', onClientError)
       // Used for trigram indexes, e.g. on actor search
       client.query('SET pg_trgm.word_similarity_threshold TO .4;')
       if (schema) {
@@ -83,3 +85,5 @@ export class Database {
 }
 
 export default Database
+
+const onClientError = (err: Error) => dbLogger.error({ err }, 'db client error')
diff --git a/packages/bsky/tests/db.test.ts b/packages/bsky/tests/db.test.ts
index 565f07a0e73..5f92a515586 100644
--- a/packages/bsky/tests/db.test.ts
+++ b/packages/bsky/tests/db.test.ts
@@ -1,4 +1,5 @@
 import { once } from 'events'
+import { sql } from 'kysely'
 import { wait } from '@atproto/common'
 import { TestNetwork } from '@atproto/dev-env'
 import { Database } from '../src'
@@ -20,6 +21,19 @@ describe('db', () => {
     await network.close()
   })
 
+  it('handles client errors without crashing.', async () => {
+    const tryKillConnection = db.transaction(async (dbTxn) => {
+      const result = await sql`select pg_backend_pid() as pid;`.execute(
+        dbTxn.db,
+      )
+      const pid = result.rows[0]?.['pid'] as number
+      await sql`select pg_terminate_backend(${pid});`.execute(db.db)
+      await sql`select 1;`.execute(dbTxn.db)
+    })
+    // This should throw, but no unhandled error
+    await expect(tryKillConnection).rejects.toThrow()
+  })
+
   describe('transaction()', () => {
     it('commits changes', async () => {
       const result = await db.transaction(async (dbTxn) => {