add client channel cache

Maintain unused channels for 20 seconds before closing.

src/client.cpp

@@ -31,6 +31,8 @@ constexpr size_t nBuckets = 30u;
 
 constexpr size_t maxSearchPayload = 0x4000;
 
+constexpr timeval channelCacheCleanInterval{10,0};
+
 constexpr timeval beaconCleanInterval{2*180, 0};
 
 Disconnect::Disconnect()
@@ -75,7 +77,6 @@ Channel::Channel(const std::shared_ptr<Context::Pvt>& context, const std::string
 Channel::~Channel()
 {
     context->chanByCID.erase(cid);
-    context->chanByName.erase(name);
     // searchBuckets cleaned in tickSearch()
     if((state==Creating || state==Active) && conn && conn->bev) {
         {
@@ -191,7 +192,8 @@ std::shared_ptr<Channel> Channel::build(const std::shared_ptr<Context::Pvt>& con
 
     auto it = context->chanByName.find(name);
     if(it!=context->chanByName.end()) {
-        chan = it->second.lock();
+        chan = it->second;
+        chan->garbage = false;
     }
 
     if(!chan) {
@@ -266,6 +268,18 @@ void Context::hurryUp()
     });
 }
 
+void Context::cacheClear()
+{
+    if(!pvt)
+        throw std::logic_error("NULL Context");
+
+    pvt->tcp_loop.call([this](){
+        // run twice to ensure both mark and sweep of all unused channels
+        pvt->cacheClean();
+        pvt->cacheClean();
+    });
+}
+
 static
 Value buildCAMethod()
 {
@@ -286,6 +300,7 @@ Context::Pvt::Pvt(const Config& conf)
     ,searchTimer(event_new(tcp_loop.base, -1, EV_TIMEOUT, &Pvt::tickSearchS, this))
     ,manager(UDPManager::instance())
     ,beaconCleaner(event_new(manager.loop().base, -1, EV_TIMEOUT|EV_PERSIST, &Pvt::tickBeaconCleanS, this))
+    ,cacheCleaner(event_new(tcp_loop.base, -1, EV_TIMEOUT|EV_PERSIST, &Pvt::cacheCleanS, this))
 {
     effective.expand();
 
@@ -362,6 +377,8 @@ Context::Pvt::Pvt(const Config& conf)
         log_err_printf(setup, "Error enabling search RX\n%s", "");
     if(event_add(beaconCleaner.get(), &beaconCleanInterval))
         log_err_printf(setup, "Error enabling beacon clean timer on\n%s", "");
+    if(event_add(cacheCleaner.get(), &channelCacheCleanInterval))
+        log_err_printf(setup, "Error enabling channel cache clean timer on\n%s", "");
 }
 
 Context::Pvt::~Pvt() {}
@@ -373,8 +390,11 @@ void Context::Pvt::close()
         (void)event_del(searchTimer.get());
         (void)event_del(searchRx.get());
         (void)event_del(beaconCleaner.get());
+        (void)event_del(cacheCleaner.get());
 
-        decltype (connByAddr) conns(std::move(connByAddr));
+        auto conns(std::move(connByAddr));
+        // explicitly break ref. loop of channel cache
+        auto chans(std::move(chanByName));
 
         for(auto& pair : conns) {
             auto conn = pair.second.lock();
@@ -383,6 +403,11 @@ void Context::Pvt::close()
 
             conn->cleanup();
         }
+
+        conns.clear();
+        chans.clear();
+
+        assert(internal_self.use_count()==1);
     });
 
     tcp_loop.join();
@@ -739,6 +764,40 @@ void Context::Pvt::tickBeaconCleanS(evutil_socket_t fd, short evt, void *raw)
     }
 }
 
+void Context::Pvt::cacheClean()
+{
+    std::set<std::string> trash;
+
+    for(auto& pair : chanByName) {
+        if(pair.second.use_count()<=1) {
+            if(!pair.second->garbage) {
+                // mark for next sweep
+                log_debug_printf(setup, "Chan GC mark '%s'\n", pair.first.c_str());
+                pair.second->garbage = true;
+
+            } else {
+                // sweep
+                trash.insert(pair.first);
+            }
+        }
+    }
+
+    // explicitly break ref. loop of channel cache
+    for(auto& name : trash) {
+        chanByName.erase(name);
+        log_debug_printf(setup, "Chan GC sweep '%s'\n", name.c_str());
+    }
+}
+
+void Context::Pvt::cacheCleanS(evutil_socket_t fd, short evt, void *raw)
+{
+    try {
+        static_cast<Pvt*>(raw)->tickBeaconClean();
+    }catch(std::exception& e){
+        log_exc_printf(io, "Unhandled error in beacon cleaner timer callback: %s\n", e.what());
+    }
+}
+
 } // namespace client
 
 } // namespace pvxs