Overlay tuning and logging improvements:

Adjust overlay tuning to reflect measured behavior of the
network under increased load.

Improve logging of peer sendq size and disconnect reasons.

src/ripple/overlay/impl/PeerImp.cpp

@@ -210,6 +210,12 @@ PeerImp::send (Message::pointer const& m)
         // a small senq periodically
         large_sendq_ = 0;
     }
+    else if ((sendq_size % Tuning::sendQueueLogFreq) == 0)
+    {
+        JLOG (journal_.debug()) <<
+            (name_.empty() ? remote_address_.to_string() : name_) <<
+                " sendq: " << sendq_size;
+    }
 
     send_queue_.push(m);
 
@@ -442,7 +448,9 @@ PeerImp::fail(std::string const& reason)
                 shared_from_this(), reason));
     if (socket_.is_open())
     {
-        JLOG (journal_.debug()) << reason;
+        JLOG (journal_.warn()) <<
+            (name_.empty() ? remote_address_.to_string() : name_) <<
+                " failed: " << reason;
     }
     close();
 }

src/ripple/overlay/impl/Tuning.h

@@ -52,13 +52,13 @@ enum
 
     /** How many milliseconds to consider high latency
         on a peer connection */
-    peerHighLatency     =  250,
+    peerHighLatency     =  300,
 
     /** How often we check connections (seconds) */
-    checkSeconds        =   10,
+    checkSeconds        =   32,
 
     /** How often we latency/sendq probe connections */
-    timerSeconds        =    4,
+    timerSeconds        =    8,
 
     /** How many timer intervals a sendq has to stay large before we disconnect */
     sendqIntervals      =    4,
@@ -67,10 +67,13 @@ enum
     noPing              =   10,
 
     /** How many messages on a send queue before we refuse queries */
-    dropSendQueue       =    8,
+    dropSendQueue       =   192,
 
     /** How many messages we consider reasonable sustained on a send queue */
-    targetSendQueue     =   16,
+    targetSendQueue     =   128,
+
+    /** How often to log send queue size */
+    sendQueueLogFreq    =    64,
 };
 
 } // Tuning