From 6684edaeaf60ec601414f14eec4215c06fa65646 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Sat, 25 May 2024 12:13:55 -0500
Subject: [PATCH] pipeline: fix race condition in encounterEvent

---
 src/pipeline.ts | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/src/pipeline.ts b/src/pipeline.ts
index 7bab6d0..a540125 100644
--- a/src/pipeline.ts
+++ b/src/pipeline.ts
@@ -3,12 +3,14 @@ import { LNURL } from '@nostrify/nostrify/ln';
 import { PipePolicy } from '@nostrify/nostrify/policies';
 import Debug from '@soapbox/stickynotes/debug';
 import { sql } from 'kysely';
+import { LRUCache } from 'lru-cache';
 
 import { Conf } from '@/config.ts';
 import { DittoDB } from '@/db/DittoDB.ts';
 import { deleteAttachedMedia } from '@/db/unattached-media.ts';
 import { DittoEvent } from '@/interfaces/DittoEvent.ts';
 import { DVM } from '@/pipeline/DVM.ts';
+import { MuteListPolicy } from '@/policies/MuteListPolicy.ts';
 import { RelayError } from '@/RelayError.ts';
 import { hydrateEvents, purifyEvent } from '@/storages/hydrate.ts';
 import { Storages } from '@/storages.ts';
@@ -23,8 +25,6 @@ import { nip05Cache } from '@/utils/nip05.ts';
 import { updateStats } from '@/utils/stats.ts';
 import { getTagSet } from '@/utils/tags.ts';
 
-import { MuteListPolicy } from '@/policies/MuteListPolicy.ts';
-
 const debug = Debug('ditto:pipeline');
 
 /**
@@ -33,7 +33,7 @@ const debug = Debug('ditto:pipeline');
  */
 async function handleEvent(event: DittoEvent, signal: AbortSignal): Promise<void> {
   if (!(await verifyEventWorker(event))) return;
-  if (await encounterEvent(event, signal)) return;
+  if (encounterEvent(event)) return;
   debug(`NostrEvent<${event.kind}> ${event.id}`);
 
   if (event.kind !== 24133) {
@@ -90,17 +90,15 @@ async function policyFilter(event: NostrEvent): Promise<void> {
   }
 }
 
+const encounters = new LRUCache<string, true>({ max: 1000 });
+
 /** Encounter the event, and return whether it has already been encountered. */
-async function encounterEvent(event: NostrEvent, signal: AbortSignal): Promise<boolean> {
-  const cache = await Storages.cache();
-  const reqmeister = await Storages.reqmeister();
-
-  const [existing] = await cache.query([{ ids: [event.id], limit: 1 }]);
-
-  cache.event(event);
-  reqmeister.event(event, { signal });
-
-  return !!existing;
+function encounterEvent(event: NostrEvent): boolean {
+  const encountered = !!encounters.get(event.id);
+  if (!encountered) {
+    encounters.set(event.id, true);
+  }
+  return encountered;
 }
 
 /** Hydrate the event with the user, if applicable. */