feat(mix): adaptive service-peer discovery top-up via broker

Add a generic runServicePeerTopUp loop in waku_node that, while a service's provider count is below target, pulls more peers through the ServicePeersRequest broker; wired for mix in WakuNode.start(). Move the ServicePeersRequest provider registration into the startProvidersAndListeners/stopProvidersAndListeners lifecycle (gated on kademlia) so chat2mix gets it too, keeping WakuKademlia generic. Also fix pre-existing chat2mix build errors (toHashSet, valueOr, std/sets import).

apps/chat2mix/chat2mix.nim

@@ -6,7 +6,7 @@ when not (compileOption("threads")):
 
 {.push raises: [].}
 
-import std/[strformat, strutils, times, options, random, sequtils]
+import std/[strformat, strutils, times, options, random, sequtils, sets]
 import
   confutils,
   chronicles,
@@ -563,7 +563,7 @@ proc processInput(rfd: AsyncFD, rng: crypto.Rng) {.async.} =
     var kadBootstrapPeers: seq[(PeerId, seq[MultiAddress])]
     for nodeStr in conf.kadBootstrapNodes:
       let (peerId, ma) = block:
-        parseFullAddress(nodeStr).isOkOr:
+        parseFullAddress(nodeStr).valueOr:
           error "Failed to parse kademlia bootstrap node", node = nodeStr, error
           continue
 
@@ -573,7 +573,7 @@ proc processInput(rfd: AsyncFD, rng: crypto.Rng) {.async.} =
       node.mountKademlia(
         KademliaDiscoveryConf(
           bootstrapNodes: kadBootstrapPeers,
-          servicesToDiscover: @[MixProtocolID],
+          servicesToDiscover: toHashSet(@[MixProtocolID]),
           randomLookupInterval: chronos.seconds(60),
           serviceLookupInterval: chronos.seconds(60),
           kadDhtConfig: KadDHTConfig.new(),

logos_delivery/waku/factory/node_factory.nim

@@ -183,17 +183,6 @@ proc setupProtocols(
     node.mountKademlia(kadConf).isOkOr:
       return err("failed to setup service discovery: " & error)
 
-    # Register ServicePeersRequest provider
-    ServicePeersRequest.setProvider(
-      node.brokerCtx,
-      proc(serviceId: string): Future[Result[ServicePeersRequest, string]] {.async.} =
-        let peers = (await node.wakuKademlia.lookupServicePeers(serviceId)).valueOr:
-          return err("failed call to lookupServicePeers: " & error)
-        return ok(ServicePeersRequest(serviceId: serviceId, peers: peers)),
-    ).isOkOr:
-      error "Can't set provider for ServicePeersRequest", error = error
-      return err("Can't set provider for ServicePeersRequest: " & error)
-
   if conf.storeServiceConf.isSome():
     let storeServiceConf = conf.storeServiceConf.get()
 

logos_delivery/waku/node/waku_node.nim

@@ -62,6 +62,7 @@ import
     events/health_events,
     events/message_events,
     events/peer_events,
+    events/discovery_events,
   ],
   logos_delivery/waku/discovery/waku_kademlia,
   logos_delivery/waku/net/[bound_ports, net_config],
@@ -123,6 +124,7 @@ type
     libp2pPing*: Ping
     rng*: crypto.Rng
     brokerCtx*: BrokerContext
+    mixTopUpLoop: Future[void]
     wakuRendezvous*: WakuRendezVous
     wakuRendezvousClient*: rendezvous_client.WakuRendezVousClient
     announcedAddresses*: seq[MultiAddress]
@@ -394,6 +396,26 @@ proc mountKademlia*(
 
   return ok()
 
+proc runServicePeerTopUp(
+    node: WakuNode,
+    serviceId: string,
+    target: int,
+    currentCount: proc(): int {.gcsafe, raises: [].},
+    interval: Duration,
+) {.async.} =
+  ## Adaptive service-peer discovery: while the number of usable providers for
+  ## `serviceId` is below `target`, pull more through the broker. The registered
+  ## ServicePeersRequest provider (kademlia) performs the lookup and fills the
+  ## pool. Generic — the caller supplies the service id, target and count getter.
+  debug "service peer top-up loop started", serviceId, target, interval = $interval
+  while true:
+    await sleepAsync(interval)
+    if currentCount() >= target:
+      continue
+    let res = await ServicePeersRequest.request(node.brokerCtx, serviceId)
+    if res.isErr:
+      debug "service peer top-up request failed", serviceId, error = res.error
+
 ## Waku Sync
 
 proc mountStoreSync*(
@@ -620,10 +642,22 @@ proc startProvidersAndListeners*(node: WakuNode) =
   ).isOkOr:
     error "Can't set provider for RequestContentTopicsHealth", error = error
 
+  # Service-peer lookups are answered by kademlia; register only when it's mounted.
+  if not node.wakuKademlia.isNil():
+    ServicePeersRequest.setProvider(
+      node.brokerCtx,
+      proc(serviceId: string): Future[Result[ServicePeersRequest, string]] {.async.} =
+        let peers = (await node.wakuKademlia.lookupServicePeers(serviceId)).valueOr:
+          return err("failed call to lookupServicePeers: " & error)
+        return ok(ServicePeersRequest(serviceId: serviceId, peers: peers)),
+    ).isOkOr:
+      error "Can't set provider for ServicePeersRequest", error = error
+
 proc stopProvidersAndListeners*(node: WakuNode) =
   RequestRelayShard.clearProvider(node.brokerCtx)
   RequestContentTopicsHealth.clearProvider(node.brokerCtx)
   RequestShardTopicsHealth.clearProvider(node.brokerCtx)
+  ServicePeersRequest.clearProvider(node.brokerCtx)
 
 proc start*(node: WakuNode) {.async.} =
   ## Starts a created Waku Node and
@@ -672,6 +706,20 @@ proc start*(node: WakuNode) {.async.} =
   if not node.wakuKademlia.isNil():
     await node.wakuKademlia.start()
 
+    # Keep the mix pool filled: the generic service-peer top-up wired with
+    # mix's service id, target pool size and current pool-size getter.
+    if not node.wakuMix.isNil():
+      node.mixTopUpLoop = node.runServicePeerTopUp(
+        MixProtocolID,
+        minMixPoolSize,
+        proc(): int {.gcsafe, raises: [].} =
+          if node.wakuMix.isNil():
+            0
+          else:
+            node.getMixNodePoolSize(),
+        chronos.seconds(5),
+      )
+
   if not node.wakuFilterClient.isNil():
     node.wakuFilterClient.registerPushHandler(
       proc(pubsubTopic: PubsubTopic, msg: WakuMessage) {.async, gcsafe.} =
@@ -698,6 +746,10 @@ proc stop*(node: WakuNode) {.async.} =
 
   node.stopProvidersAndListeners()
 
+  if not node.mixTopUpLoop.isNil():
+    await node.mixTopUpLoop.cancelAndWait()
+    node.mixTopUpLoop = nil
+
   if not node.wakuKademlia.isNil():
     await node.wakuKademlia.stop()
 

logos_delivery/waku/waku_mix/protocol.nim

@@ -27,7 +27,7 @@ import
 logScope:
   topics = "waku mix"
 
-const minMixPoolSize = 4
+const minMixPoolSize* = 4
 
 type
   PublishMessage* = proc(message: WakuMessage): Future[Result[void, string]] {.