move metadata updates into their own thread pool to prevent traffic thread pool exhaustion from failed metadata updates; add better logic around checking in-flight and pending metadata announcements to peers; add checking to drop an update entirely if the peer disappears;

src/fne/network/MetadataNetwork.cpp

@@ -42,7 +42,7 @@ MetadataNetwork::MetadataNetwork(HostFNE* host, TrafficNetwork* trafficNetwork,
     m_status(NET_STAT_INVALID),
     m_peerReplicaActPkt(),
     m_peerTreeListPkt(),
-    m_threadPool(workerCnt, "diag")
+    m_threadPool(workerCnt, "meta")
 {
     assert(trafficNetwork != nullptr);
     assert(host != nullptr);

src/fne/network/TrafficNetwork.cpp

@@ -141,6 +141,9 @@ TrafficNetwork::TrafficNetwork(HostFNE* host, const std::string& address, uint16
     m_jitterMaxSize(4U),
     m_jitterMaxWait(40000U),
     m_threadPool(workerCnt, "fne"),
+    m_metadataUpdateThreadPool(workerCnt / 2U, "mupdt"),
+    m_metadataUpdateMutex(),
+    m_metadataUpdateState(),
     m_disablePacketData(false),
     m_dumpPacketData(false),
     m_verbosePacketData(false),
@@ -724,6 +727,9 @@ bool TrafficNetwork::open()
     // start thread pool
     m_threadPool.start();
 
+    // start metadata thread pool
+    m_metadataUpdateThreadPool.start();
+
     // start FluxQL thread pool
     if (m_enableInfluxDB) {
         influxdb::detail::TSCaller::start();
@@ -780,6 +786,16 @@ void TrafficNetwork::close()
     m_threadPool.stop();
     m_threadPool.wait();
 
+    // stop metadata thread pool
+    m_metadataUpdateThreadPool.stop();
+    m_metadataUpdateThreadPool.wait();
+
+    // scope is intentional
+    {
+        std::lock_guard<std::mutex> lock(m_metadataUpdateMutex);
+        m_metadataUpdateState.clear();
+    }
+
     // stop FluxQL thread pool
     if (m_enableInfluxDB) {
         influxdb::detail::TSCaller::stop();
@@ -2408,17 +2424,63 @@ void TrafficNetwork::processInCallCtrl(network::NET_ICC::ENUM command, network::
 
 void TrafficNetwork::peerMetadataUpdate(uint32_t peerId)
 {
+    if (peerId == 0U) {
+        return;
+    }
+
+    bool enqueueTask = false;
+
+    // scope is intentional
+    {
+        std::lock_guard<std::mutex> lock(m_metadataUpdateMutex);
+        MetadataUpdateState& state = m_metadataUpdateState[peerId];
+
+        if (state.inFlight) {
+            // coalesce duplicate requests while one update is running
+            LogWarning(LOG_MASTER, "PEER %u metadata update already in flight, coalescing duplicate request", peerId);
+            state.pending = true;
+            return;
+        }
+
+        if (state.pending) {
+            // a request is already queued for this peer
+            LogWarning(LOG_MASTER, "PEER %u metadata update already pending, coalescing duplicate request", peerId);
+            return;
+        }
+
+        state.pending = true;
+        enqueueTask = true;
+    }
+
+    if (!enqueueTask) {
+        return;
+    }
+
     MetadataUpdateRequest* req = new MetadataUpdateRequest();
     req->obj = this;
     req->peerId = peerId;
 
     // enqueue the task
-    if (!m_threadPool.enqueue(new_pooltask(taskMetadataUpdate, req))) {
+    if (!m_metadataUpdateThreadPool.enqueue(new_pooltask(taskMetadataUpdate, req))) {
         LogError(LOG_NET, "Failed to task enqueue metadata update, peerId = %u", peerId);
-        if (req != nullptr)
+
+        // scope is intentional
+        {
+            std::lock_guard<std::mutex> lock(m_metadataUpdateMutex);
+            auto it = m_metadataUpdateState.find(peerId);
+            if (it != m_metadataUpdateState.end()) {
+                it->second.pending = false;
+                if (!it->second.inFlight) {
+                    m_metadataUpdateState.erase(it);
+                }
+            }
+        }
+
+        if (req != nullptr) {
             delete req;
         }
     }
+}
 
 /* Helper to send the network metadata to the specified peer in a separate thread. */
 
@@ -2435,6 +2497,44 @@ void TrafficNetwork::taskMetadataUpdate(MetadataUpdateRequest* req)
         if (req == nullptr)
             return;
 
+        while (true) {
+            // scope is intentional
+            {
+                std::lock_guard<std::mutex> lock(network->m_metadataUpdateMutex);
+
+                // check if there is a pending metadata update for this peer
+                MetadataUpdateState& state = network->m_metadataUpdateState[req->peerId];
+                if (!state.pending) {
+                    // no pending metadata update for this peer, exit the loop
+                    state.inFlight = false;
+                    network->m_metadataUpdateState.erase(req->peerId);
+                    break;
+                }
+
+                // check if the peer connection is still valid and connected
+                FNEPeerConnection* connection = network->m_peers[req->peerId];
+                if (connection != nullptr) {
+                    if (!connection->connected()) {
+                        // peer connection is not connected, skip the metadata update
+                        LogWarning(LOG_MASTER, "PEER %u (%s) not connected, skipping metadata update", req->peerId, connection->identWithQualifier().c_str());
+                        state.pending = false;
+                        state.inFlight = false;
+                        network->m_metadataUpdateState.erase(req->peerId);
+                        break;
+                    }
+                } else {
+                    // peer connection is not found, skip the metadata update
+                    LogWarning(LOG_MASTER, "PEER %u not found, skipping metadata update", req->peerId);
+                    state.pending = false;
+                    state.inFlight = false;
+                    network->m_metadataUpdateState.erase(req->peerId);
+                    break;
+                }
+
+                state.pending = false;
+                state.inFlight = true;
+            }
+
             std::string peerIdentity = network->resolvePeerIdentity(req->peerId);
 
             FNEPeerConnection* connection = network->m_peers[req->peerId];
@@ -2468,6 +2568,7 @@ void TrafficNetwork::taskMetadataUpdate(MetadataUpdateRequest* req)
                     connection->unlock();
                 }
             }
+        }
 
         delete req;
     }

src/fne/network/TrafficNetwork.h

@@ -404,6 +404,24 @@ namespace network
         uint32_t m_jitterMaxWait;
 
         ThreadPool m_threadPool;
+        ThreadPool m_metadataUpdateThreadPool;
+
+        /**
+         * @brief Represents the state of a metadata update for a given peer ID.
+         * @ingroup fne_network
+         */
+        struct MetadataUpdateState {
+            /**
+             * @brief Flag indicating whether a metadata update is currently in flight for this peer ID.
+             */
+            bool inFlight = false;
+            /**
+             * @brief Flag indicating whether a metadata update is pending for this peer ID.
+             */
+            bool pending = false;
+        };
+        std::mutex m_metadataUpdateMutex;
+        std::unordered_map<uint32_t, MetadataUpdateState> m_metadataUpdateState;
 
         bool m_disablePacketData;
         bool m_dumpPacketData;