fix(relayer): Suppress duplicate event data from external listeners

src/utils/EventUtils.ts

@@ -52,6 +52,7 @@ type QuorumEvent = Log & { providers: string[] };
 export class EventManager {
   public readonly chain: string;
   public readonly events: { [blockNumber: number]: QuorumEvent[] } = {};
+  public readonly finalisedEvents: { [eventKey: string]: boolean } = {};
 
   private blockNumber: number;
 
@@ -109,6 +110,12 @@ export class EventManager {
     const events = (this.events[event.blockNumber] ??= []);
     const storedEvent = this.findEvent(event);
 
+    const eventKey = this.hashEvent(event);
+    if (this.finalisedEvents[eventKey]) {
+      // Nothing to do - this event has already been handled.
+      return;
+    }
+
     // Store or update the set of events for this block number.
     if (!isDefined(storedEvent)) {
       // Event hasn't been seen before, so store it.
@@ -173,6 +180,11 @@ export class EventManager {
         }
 
         quorumEvents.push(event);
+
+        // Protect against re-sending this event if it later arrives from another provider.
+        const eventKey = this.hashEvent(event);
+        this.finalisedEvents[eventKey] = true;
+
         return false;
       });
     });

test/EventManager.ts

@@ -7,7 +7,7 @@ import { createSpyLogger, expect, randomAddress } from "./utils";
 
 describe("EventManager: Event Handling ", async function () {
   const chainId = CHAIN_IDs.MAINNET;
-  const providers = ["infura", "alchemy", "llamanodes"];
+  const providers = ["infura", "alchemy", "llamanodes", "quicknode"];
 
   const randomNumber = (ceil = 1_000_000) => Math.floor(Math.random() * ceil);
   const makeHash = () => ethersUtils.id(randomNumber().toString());
@@ -121,4 +121,28 @@ describe("EventManager: Event Handling ", async function () {
     const hash = eventMgr.hashEvent(log);
     expect(hash).to.exist;
   });
+
+  it("Does not submit duplicate events", async function () {
+    expect(quorum).to.equal(2);
+
+    const [provider1, provider2, provider3, provider4] = providers;
+
+    // Add the event once (not finalised).
+    eventMgr.add(eventTemplate, provider1);
+    let events = eventMgr.tick(eventTemplate.blockNumber + 1);
+    expect(events.length).to.equal(0);
+
+    // Add the same event from a different provider.
+    eventMgr.add(eventTemplate, provider2);
+    events = eventMgr.tick(eventTemplate.blockNumber + 1);
+    expect(events.length).to.equal(1);
+
+    // Re-add the same event again, from two new providers.
+    eventMgr.add(eventTemplate, provider3);
+    eventMgr.add(eventTemplate, provider4);
+
+    // Verify that the same event was not replayed.
+    events = eventMgr.tick(eventTemplate.blockNumber + 1);
+    expect(events.length).to.equal(0);
+  });
 });