client: re-define the meaning of poke()

src/client.cpp

@@ -27,25 +27,45 @@ typedef epicsGuardRelease<epicsMutex> UnGuard;
 namespace pvxs {
 namespace client {
 
+namespace {
+/* "normal" tick interval for the search bucket ring, and "fast" interval
+ * used for one revolution after a successful poke().
+ */
 constexpr timeval bucketInterval{1,0};
+constexpr timeval bucketIntervalFast{0,200000};
+// coalescence time for first search for a batch of newly created Channels
 constexpr timeval initialSearchDelay{0, 10000}; // 10 ms
+// number of buckets in the search ring
 constexpr size_t nBuckets = 30u;
 
-// try not to fragment with usual MTU==1500
+/* our limit for UDP packet payload.
+ * try not to fragment with usual MTU==1500 allowing for some overhead
+ * by transport protocols.  Ethernet+ip+udp headers add >= 42 bytes.
+ * May be more with eg. IP header options, VLAN tag, etc.
+ */
 constexpr size_t maxSearchPayload = 1400;
 
+/* Interval between checks for Channels which are no longer used by any operation.
+ * Channels will be discarded if found to be unused by two consecutive checks.
+ */
 constexpr timeval channelCacheCleanInterval{10,0};
 
+// time to wait before allowing another hurryUp().
+constexpr double pokeHoldoff = 30.0;
+
 // limit on the number of GUIDs * protocols * addresses we will track
 constexpr size_t beaconTrackLimit{20000};
 
+// interval between checks to discard servers which have stopped sending beacons
 constexpr timeval beaconCleanInterval{180, 0};
 
+// special interval to attempt to reconnect to disconnected name servers
 constexpr timeval tcpNSCheckInterval{10, 0};
 
 // searchSequenceID in CMD_SEARCH is redundant.
 // So we use a static value and instead rely on IDs for individual PVs
 constexpr uint32_t search_seq{0x66696e64}; // "find"
+} // namespace
 
 Disconnect::Disconnect()
     :std::runtime_error("Disconnected")
@@ -399,7 +419,7 @@ void Context::hurryUp()
         throw std::logic_error("NULL Context");
 
     pvt->impl->manager.loop().call([this](){
-        pvt->impl->poke(true);
+        pvt->impl->poke();
     });
 }
 
@@ -672,22 +692,22 @@ void ContextImpl::close()
     manager.sync();
 }
 
-void ContextImpl::poke(bool force)
+void ContextImpl::poke()
 {
     {
         Guard G(pokeLock);
-        if(poked)
+        if(nPoked)
             return;
 
         epicsTimeStamp now{};
 
         double age = -1.0;
-        if(!force && (epicsTimeGetCurrent(&now) || (age=epicsTimeDiffInSeconds(&now, &lastPoke))<30.0)) {
+        if(epicsTimeGetCurrent(&now) || (age=epicsTimeDiffInSeconds(&now, &lastPoke))<pokeHoldoff) {
             log_debug_printf(setup, "Ignoring hurryUp() age=%.1f sec\n", age);
             return;
         }
         lastPoke = now;
-        poked = true;
+        nPoked = nBuckets;
     }
 
     log_debug_printf(setup, "hurryUp()%s\n", "");
@@ -782,7 +802,7 @@ void ContextImpl::onBeacon(const UDPManager::Beacon& msg)
                                now
                     });
 
-        poke(false);
+        poke();
     }
 }
 
@@ -973,7 +993,7 @@ void ContextImpl::onSearchS(evutil_socket_t fd, short evt, void *raw)
     }
 }
 
-void ContextImpl::tickSearch(SearchKind kind)
+void ContextImpl::tickSearch(SearchKind kind, bool poked)
 {
     // If kind == SearchKind::discover, then this is a discovery ping.
     // these are really empty searches with must-reply set.
@@ -1074,7 +1094,7 @@ void ContextImpl::tickSearch(SearchKind kind)
             count++;
 
             size_t ninc = 0u;
-            if(kind==SearchKind::check)
+            if(kind==SearchKind::check && !poked)
                 ninc = chan->nSearch = std::min(searchBuckets.size(), chan->nSearch+1u);
             auto next = (idx + ninc)%searchBuckets.size();
             auto nextnext = (next + 1u)%searchBuckets.size();
@@ -1174,14 +1194,18 @@ void ContextImpl::tickSearchS(evutil_socket_t fd, short evt, void *raw)
 {
     auto self(static_cast<ContextImpl*>(raw));
     try {
+        bool poke = false;
         {
             Guard G(self->pokeLock);
-            self->poked = false;
+            if(self->nPoked) {
+                poke = true;
+                self->nPoked--;
+            }
         }
 
-        self->tickSearch(SearchKind::check);
+        self->tickSearch(SearchKind::check, poke);
 
-        if(event_add(self->searchTimer.get(), &bucketInterval))
+        if(event_add(self->searchTimer.get(), poke ? &bucketIntervalFast : &bucketInterval))
             log_err_printf(setup, "Error re-enabling search timer on\n%s", "");
 
     }catch(std::exception& e){
@@ -1194,7 +1218,7 @@ void ContextImpl::initialSearchS(evutil_socket_t fd, short evt, void *raw)
     auto self(static_cast<ContextImpl*>(raw));
     try {
         self->initialSearchScheduled = false;
-        self->tickSearch(SearchKind::initial);
+        self->tickSearch(SearchKind::initial, false);
     }catch(std::exception& e){
         log_exc_printf(io, "Unhandled error in initial search callback: %s\n", e.what());
     }

src/clientconn.cpp

@@ -310,7 +310,7 @@ void Connection::handle_CONNECTION_VALIDATED()
 
     if(nameserver) {
         log_info_printf(io, "(re)connected to nameserver %s\n", peerName.c_str());
-        context->poke(true);
+        context->poke();
     }
 }
 

src/clientdiscover.cpp

@@ -93,7 +93,7 @@ std::shared_ptr<Operation> DiscoverBuilder::exec()
         if(first && ping) {
             log_debug_printf(setup, "Starting Discover%s", "\n");
 
-            context->tickSearch(ContextImpl::SearchKind::discover);
+            context->tickSearch(ContextImpl::SearchKind::discover, false);
         }
     });
 

src/clientimpl.h

@@ -269,7 +269,7 @@ struct ContextImpl : public std::enable_shared_from_this<ContextImpl>
     // poked and beaconSenders from both TCP and UDP workers
     epicsMutex pokeLock;
     epicsTimeStamp lastPoke{};
-    bool poked = false;
+    size_t nPoked = 0u;
 
     // unlike `poke`, `scheduleInitialSearch` is only ever called from the
     // tcp_loop so this does not need to be guarded by a mutex
@@ -332,7 +332,7 @@ struct ContextImpl : public std::enable_shared_from_this<ContextImpl>
 
     void close();
 
-    void poke(bool force);
+    void poke();
 
     void serverEvent(const Discovered &evt);
 
@@ -343,7 +343,7 @@ struct ContextImpl : public std::enable_shared_from_this<ContextImpl>
     bool onSearch(evutil_socket_t fd);
     static void onSearchS(evutil_socket_t fd, short evt, void *raw);
     enum class SearchKind { discover, initial, check };
-    void tickSearch(SearchKind kind);
+    void tickSearch(SearchKind kind, bool poked);
     static void tickSearchS(evutil_socket_t fd, short evt, void *raw);
     static void initialSearchS(evutil_socket_t fd, short evt, void *raw);
     void tickBeaconClean();