chore: add idontwants cacheSize metric

src/index.ts

@@ -430,6 +430,9 @@ export class GossipSub extends TypedEventEmitter<GossipsubEvents> implements Pub
 
   /**
    * Tracks IDONTWANT messages received by peers and the heartbeat they were received in
+   *
+   * idontwants are stored for `mcacheLength` heartbeats before being pruned,
+   * so this map is bounded by peerCount * idontwantMaxMessages * mcacheLength
    */
   private readonly idontwants = new Map<PeerIdStr, Map<MsgIdStr, number>>()
 
@@ -3176,6 +3179,12 @@ export class GossipSub extends TypedEventEmitter<GossipsubEvents> implements Pub
     }
     metrics.cacheSize.set({ cache: 'backoff' }, backoffSize)
 
+    let idontwantsCount = 0
+    for (const idontwant of this.idontwants.values()) {
+      idontwantsCount += idontwant.size
+    }
+    metrics.cacheSize.set({ cache: 'idontwants' }, idontwantsCount)
+
     // Peer counts
 
     for (const [topicStr, peers] of this.topics) {

src/metrics.ts

@@ -598,10 +598,10 @@ export function getMetrics (
       name: 'gossipsub_idontwant_rcv_msgids_total',
       help: 'Total received IDONTWANT messages'
     }),
-    /** Total requested messageIDs that we don't have */
+    /** Total received IDONTWANT messageIDs that we don't have */
     idontwantRcvDonthaveMsgids: register.gauge({
       name: 'gossipsub_idontwant_rcv_dont_have_msgids_total',
-      help: 'Total requested IDONTWANT messageIDs that we do not have in mcache'
+      help: 'Total received IDONTWANT messageIDs that we do not have in mcache'
     }),
     iwantPromiseStarted: register.gauge({
       name: 'gossipsub_iwant_promise_sent_total',