diff --git a/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp b/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp
index 3a0da40d7f3..0441534af72 100644
--- a/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp
+++ b/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp
@@ -15,6 +15,7 @@
     limitations under the License.
 ############################################################################## */
 
+#include <cmath>
 #include "thactivityutil.ipp"
 #include "thcompressutil.hpp"
 #include "thexception.hpp"
@@ -155,6 +156,8 @@ class CBroadcaster : public CSimpleInterface
         CThreadedPersistent threaded;
         SimpleInterThreadQueueOf<CSendItem, true> broadcastQueue;
         Owned<IException> exception;
+        unsigned myNode;
+        unsigned nodes;
         bool aborted;
         void clearQueue()
         {
@@ -169,6 +172,12 @@ class CBroadcaster : public CSimpleInterface
         CSend(CBroadcaster &_broadcaster) : threaded("CBroadcaster::CSend", this), broadcaster(_broadcaster)
         {
             aborted = false;
+            myNode = broadcaster.activity.queryJob().queryMyNodeRank()-1; // 0 based
+            nodes = broadcaster.activity.queryJob().queryNodes();
+
+            // in theory each worker could be sending log(n) packets, with the broadcaster on each blocking waiting for acks
+            unsigned limit = nodes * std::ceil(std::log2(nodes));
+            broadcastQueue.setLimit(limit);
         }
         ~CSend()
         {
@@ -182,7 +191,22 @@ class CBroadcaster : public CSimpleInterface
                     sendItem->Release();
                 throw exception.getClear();
             }
-            broadcastQueue.enqueue(sendItem); // will block if queue full
+            // check if anywhere else to send to
+            if (sendItem)
+            {
+                unsigned origin = sendItem->queryNode();
+                unsigned pseudoNode = (myNode<origin) ? nodes-origin+myNode : myNode-origin;
+                unsigned t = broadcaster.target(0, pseudoNode);
+                if (t>=nodes)
+                {
+                    sendItem->Release();
+                    return;
+                }
+            }
+            while (!broadcastQueue.enqueue(sendItem, 5000)) // will block if queue full
+            {
+                DBGLOG("CSend::addBlock() - broadcastQueue full, waiting for space");
+            }
         }
         void start()
         {
@@ -272,6 +296,8 @@ class CBroadcaster : public CSimpleInterface
         mptag_t rt = ::createReplyTag();
         unsigned origin = sendItem->queryNode();
         unsigned pseudoNode = (myNode<origin) ? nodes-origin+myNode : myNode-origin;
+
+        // NB: could in theory spot if all descendents that this would end up propagating to have stopped, and not send
         CMessageBuffer replyMsg;
         // sends to all in 1st pass, then waits for ack from all
         for (unsigned sendRecv=0; sendRecv<2 && !activity.queryAbortSoon(); sendRecv++)
@@ -306,6 +332,10 @@ class CBroadcaster : public CSimpleInterface
 #endif
                     if (!activity.receiveMsg(comm, replyMsg, t, rt))
                         break;
+                    bool isStopping;
+                    replyMsg.read(isStopping);
+                    if (isStopping) // effectively a shortcut to mark asap that sender is stopping because the receiver has been requested to stop
+                        setStopping(t-1);
 #ifdef _TRACEBROADCAST
                     ActPrintLog(&activity, "Broadcast node %d Sent to node %d, origin node %d, origin slave %d, size %d, code=%d - received ack", myNode+1, t, origin+1, sendItem->querySlave()+1, sendLen, (unsigned)sendItem->queryCode());
 #endif
@@ -330,6 +360,11 @@ class CBroadcaster : public CSimpleInterface
         }
         return false;
     }
+    // recieve loop, receives CSendItem packets, adds them to broadcaster thread ('sender'), and processes the packet via 'bCastReceive'.
+    // bcast_sendStopping are regular row packets that inform us that the sender is stopping (something upstream has asked it to stop())
+    // - If all workers have signalled stopping, 'allRequestStop' will be set and will curtail the broadcast of more packets.
+    // - Or, if the broadcaster has explicitly been stopped (occurs via failover to local lookup), this will also curtail the broadcast of more packets.
+    // bcast_stop contains no row data, it signals that the sender has finished sending data.
     void recvLoop()
     {
         // my sender is implicitly stopped (never sends to self)
@@ -349,16 +384,20 @@ class CBroadcaster : public CSimpleInterface
                 break;
             }
             mptag_t replyTag = msg.getReplyTag();
-            CMessageBuffer ackMsg;
             Owned<CSendItem> sendItem = new CSendItem(msg);
 #ifdef _TRACEBROADCAST
             ActPrintLog(&activity, "Broadcast node %d received from node %d, origin node %d, origin slave %d, size %d, code=%d", myNode+1, (unsigned)sendRank, sendItem->queryNode()+1, sendItem->querySlave()+1, sendItem->length(), (unsigned)sendItem->queryCode());
 #endif
+            CMessageBuffer ackMsg;
+            bool stopping = isStopping(); // this is effectively a shortcut to inform sender asap. bcast_sendStopping/bcast_stop will be queued soon
+            ackMsg.append(stopping);
             comm.send(ackMsg, sendRank, replyTag); // send ack
 #ifdef _TRACEBROADCAST
             ActPrintLog(&activity, "Broadcast node %d, sent ack to node %d, replyTag=%d", myNode+1, (unsigned)sendRank, (unsigned)replyTag);
 #endif
-            sender.addBlock(sendItem.getLink());
+            // if all stopping, then suppress broadcasting (except stop packets)
+            if (!allRequestStop || (bcast_stop == sendItem->queryCode()))
+                sender.addBlock(sendItem.getLink());
             assertex(myNode != sendItem->queryNode());
             switch (sendItem->queryCode())
             {