Process CDC timeouts in a timely manner

cpp/cdc/CDC.cpp

@@ -272,7 +272,8 @@ public:
         }
 
         LOG_DEBUG(_env, "Blocking to wait for readable sockets");
-        if (unlikely(poll(_socks.data(), _socks.size()) < 0)) {
+        // Only timeout if there are outstanding shard requests
+        if (unlikely(poll(_socks.data(), _socks.size(), (_inFlightShardReqs.size() > 0) ? _shardTimeout : -1) < 0)) {
             if (errno == EINTR) { return; }
             throw SYSCALL_EXCEPTION("poll");
         }

cpp/core/Loop.cpp

@@ -73,8 +73,9 @@ void Loop::run() {
     while (!stopLoop.load()) { step(); }
 }
 
-int Loop::poll(struct pollfd* fds, nfds_t nfds) {
-    return ppoll(fds, nfds, nullptr, &blockingSigset);
+int Loop::poll(struct pollfd* fds, nfds_t nfds, Duration timeout) {
+    struct timespec spec = timeout.timespec();
+    return ppoll(fds, nfds, &spec, &blockingSigset);
 }
 
 void Loop::stop() {

cpp/core/Loop.hpp

@@ -46,8 +46,9 @@ public:
 
     void run();
 
-    // Polls forever with SIGINT/SIGTERM unmasked.
-    int poll(struct pollfd* fds, nfds_t nfds);
+    // Polls forever with SIGINT/SIGTERM unmasked. If timeout < 0, waits forever.
+    // If timeout == 0, returns immediately. If timeout > 0, it'll wait.
+    int poll(struct pollfd* fds, nfds_t nfds, Duration timeout);
 
     // Sleeps with SIGINT/SIGTERM unmasked.
     int sleep(Duration d);

cpp/core/Xmon.cpp

@@ -251,7 +251,7 @@ EggsTime Xmon::_stepNextWakeup() {
         nextWakeup = std::min(nextWakeup, eggsNow() + HEARTBEAT_INTERVAL*2);
     }
 
-    if (poll(_fds, NUM_FDS) < 0) {
+    if (poll(_fds, NUM_FDS, -1) < 0) {
         if (errno == EINTR) { return nextWakeup; }
         throw SYSCALL_EXCEPTION("poll");
     }

cpp/shard/Shard.cpp

@@ -379,7 +379,7 @@ public:
             _sendVecs[i].clear();
         }
 
-        if (unlikely(poll(_shared.socks.data(), 1 + (_shared.socks[1].fd != 0)) < 0)) {
+        if (unlikely(poll(_shared.socks.data(), 1 + (_shared.socks[1].fd != 0), -1) < 0)) {
             if (errno == EINTR) { return; }
             throw SYSCALL_EXCEPTION("poll");
         }