From 111b194e3e6e9b6249149dd6d716c42d36915644 Mon Sep 17 00:00:00 2001
From: Lion - dapplion <35266934+dapplion@users.noreply.github.com>
Date: Mon, 4 Apr 2022 20:45:08 +0200
Subject: [PATCH] Handle unknown topic without try catch (#3881)

---
 packages/lodestar/src/network/gossip/gossipsub.ts | 9 ++++-----
 packages/lodestar/src/network/gossip/topic.ts     | 6 ++++++
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/packages/lodestar/src/network/gossip/gossipsub.ts b/packages/lodestar/src/network/gossip/gossipsub.ts
index 1e57573a796..bab213dcecc 100644
--- a/packages/lodestar/src/network/gossip/gossipsub.ts
+++ b/packages/lodestar/src/network/gossip/gossipsub.ts
@@ -442,10 +442,10 @@ export class Eth2Gossipsub extends Gossipsub {
         // Ignore topics with 0 peers. May prevent overriding after a fork
         if (peers.size === 0) continue;
 
-        // there are some new topics in the network so we have to try/catch
+        // there are some new topics in the network so `getKnownTopic()` returns undefined
         // for example in prater: /eth2/82f4a72b/optimistic_light_client_update_v0/ssz_snappy
-        try {
-          const topic = this.gossipTopicCache.getTopic(topicString);
+        const topic = this.gossipTopicCache.getKnownTopic(topicString);
+        if (topic !== undefined) {
           if (topic.type === GossipType.beacon_attestation) {
             peersByBeaconAttSubnetByFork.set(topic.fork, topic.subnet, peers.size);
           } else if (topic.type === GossipType.sync_committee) {
@@ -453,8 +453,7 @@ export class Eth2Gossipsub extends Gossipsub {
           } else {
             peersByTypeByFork.set(topic.fork, topic.type, peers.size);
           }
-          // eslint-disable-next-line no-empty
-        } catch {}
+        }
       }
 
       // beacon attestation mesh gets counted separately so we can track mesh peers by subnet
diff --git a/packages/lodestar/src/network/gossip/topic.ts b/packages/lodestar/src/network/gossip/topic.ts
index 90621384c87..6c14b86e814 100644
--- a/packages/lodestar/src/network/gossip/topic.ts
+++ b/packages/lodestar/src/network/gossip/topic.ts
@@ -16,6 +16,7 @@ export class GossipTopicCache implements IGossipTopicCache {
 
   constructor(private readonly forkDigestContext: IForkDigestContext) {}
 
+  /** Returns cached GossipTopic, otherwise attempts to parse it from the str */
   getTopic(topicStr: string): GossipTopic {
     let topic = this.topicsByTopicStr.get(topicStr);
     if (topic === undefined) {
@@ -26,6 +27,11 @@ export class GossipTopicCache implements IGossipTopicCache {
     return topic;
   }
 
+  /** Returns cached GossipTopic, otherwise returns undefined */
+  getKnownTopic(topicStr: string): GossipTopic | undefined {
+    return this.topicsByTopicStr.get(topicStr);
+  }
+
   setTopic(topicStr: string, topic: GossipTopic): void {
     if (!this.topicsByTopicStr.has(topicStr)) {
       this.topicsByTopicStr.set(topicStr, {encoding: DEFAULT_ENCODING, ...topic});