feat: drop old msgs to be relayed

libp2p/protocols/pubsub/pubsubpeer.nim

@@ -53,10 +53,16 @@ type
   DropConn* = proc(peer: PubSubPeer) {.gcsafe, raises: [].} # have to pass peer as it's unknown during init
   OnEvent* = proc(peer: PubSubPeer, event: PubSubPeerEvent) {.gcsafe, raises: [].}
 
+  Ttlmessage* = object
+    msg*: seq[byte]
+    ttl*: Moment
+
   RpcMessageQueue* = ref object
     sendPriorityQueue: Deque[Future[void]]
-    nonPriorityQueue: AsyncQueue[seq[byte]]
+    nonPriorityQueue: AsyncQueue[Ttlmessage]
     sendNonPriorityTask: Future[void]
+    # The max duration a message to be relayed can wait to be sent before it is dropped. The default is 500ms.
+    maxDurationInNonPriorityQueue: Duration
 
   PubSubPeer* = ref object of RootObj
     getConn*: GetConn                   # callback to establish a new send connection
@@ -289,7 +295,7 @@ proc sendEncoded*(p: PubSubPeer, msg: seq[byte], isHighPriority: bool = false) {
     when defined(libp2p_expensive_metrics):
       libp2p_gossipsub_priority_queue_size.inc(labelValues = [$p.peerId])
   else:
-    await p.rpcmessagequeue.nonPriorityQueue.addLast(msg)
+    await p.rpcmessagequeue.nonPriorityQueue.addLast(Ttlmessage(msg: msg, ttl: Moment.now()))
     when defined(libp2p_expensive_metrics):
       libp2p_gossipsub_non_priority_queue_size.inc(labelValues = [$p.peerId])
   trace "message queued", p, msg = shortLog(msg)
@@ -373,10 +379,12 @@ proc sendNonPriorityTask(p: PubSubPeer) {.async.} =
      while p.rpcmessagequeue.sendPriorityQueue.len > 0:
        await p.rpcmessagequeue.sendPriorityQueue[0]
        p.clearSendPriorityQueue()
-     let msg = await p.rpcmessagequeue.nonPriorityQueue.popFirst()
+     let ttlMsg = await p.rpcmessagequeue.nonPriorityQueue.popFirst()
      when defined(libp2p_expensive_metrics):
        libp2p_gossipsub_non_priority_queue_size.dec(labelValues = [$p.peerId])
-     await p.sendMsg(msg)
+     if Moment.now() - ttlMsg.ttl >= p.rpcmessagequeue.maxDurationInNonPriorityQueue:
+       continue
+     await p.sendMsg(ttlMsg.msg)
 
 proc startSendNonPriorityTask(p: PubSubPeer) =
   debug "starting sendNonPriorityTask", p
@@ -394,10 +402,11 @@ proc stopSendNonPriorityTask*(p: PubSubPeer) =
       libp2p_gossipsub_priority_queue_size.set(labelValues = [$p.peerId], value = 0)
       libp2p_gossipsub_non_priority_queue_size.set(labelValues = [$p.peerId], value = 0)
 
-proc new(T: typedesc[RpcMessageQueue]): T =
+proc new(T: typedesc[RpcMessageQueue], maxDurationInNonPriorityQueue = 500.milliseconds): T =
   return T(
     sendPriorityQueue: initDeque[Future[void]](),
-    nonPriorityQueue: newAsyncQueue[seq[byte]](),
+    nonPriorityQueue: newAsyncQueue[Ttlmessage](),
+    maxDurationInNonPriorityQueue: maxDurationInNonPriorityQueue,
   )
 
 proc new*(