rpc: Split option -rpctimeout into -rpcservertimeout and -rpcclienttimeout

The two timeouts for the server and client, are essentially different:

- In the case of the server it should be a lower value to avoid clients
clogging up connection slots

- In the case of the client it should be a high value to accomedate slow
  responses from the server, for example for slow queries or when the
  lock is contended

Split the options into `-rpcservertimeout` and `-rpcclienttimeout` with
respective defaults of 30 and 900.

contrib/debian/examples/bitcoin.conf

@@ -73,7 +73,7 @@
 
 # How many seconds bitcoin will wait for a complete RPC HTTP request.
 # after the HTTP connection is established. 
-#rpctimeout=30
+#rpcclienttimeout=30
 
 # By default, only RPC connections from localhost are allowed.
 # Specify as many rpcallowip= settings as you like to allow connections from other hosts,

src/bitcoin-cli.cpp

@@ -22,6 +22,8 @@
 
 using namespace std;
 
+static const int DEFAULT_HTTP_CLIENT_TIMEOUT=900;
+
 std::string HelpMessageCli()
 {
     string strUsage;
@@ -37,6 +39,7 @@ std::string HelpMessageCli()
     strUsage += HelpMessageOpt("-rpcwait", _("Wait for RPC server to start"));
     strUsage += HelpMessageOpt("-rpcuser=<user>", _("Username for JSON-RPC connections"));
     strUsage += HelpMessageOpt("-rpcpassword=<pw>", _("Password for JSON-RPC connections"));
+    strUsage += HelpMessageOpt("-rpcclienttimeout=<n>", strprintf(_("Timeout during HTTP requests (default: %d)"), DEFAULT_HTTP_CLIENT_TIMEOUT));
 
     return strUsage;
 }
@@ -150,7 +153,7 @@ UniValue CallRPC(const string& strMethod, const UniValue& params)
     struct evhttp_connection *evcon = evhttp_connection_base_new(base, NULL, host.c_str(), port); // TODO RAII
     if (evcon == NULL)
         throw runtime_error("create connection failed");
-    evhttp_connection_set_timeout(evcon, GetArg("-rpctimeout", 30));
+    evhttp_connection_set_timeout(evcon, GetArg("-rpcclienttimeout", DEFAULT_HTTP_CLIENT_TIMEOUT));
 
     HTTPReply response;
     struct evhttp_request *req = evhttp_request_new(http_request_done, (void*)&response); // TODO RAII

src/httpserver.cpp

@@ -374,7 +374,7 @@ bool InitHTTPServer()
         return false;
     }
 
-    evhttp_set_timeout(http, GetArg("-rpctimeout", DEFAULT_HTTP_TIMEOUT));
+    evhttp_set_timeout(http, GetArg("-rpcservertimeout", DEFAULT_HTTP_SERVER_TIMEOUT));
     evhttp_set_max_body_size(http, MAX_SIZE);
     evhttp_set_gencb(http, http_request_cb, NULL);
 

src/httpserver.h

@@ -13,7 +13,7 @@
 
 static const int DEFAULT_HTTP_THREADS=4;
 static const int DEFAULT_HTTP_WORKQUEUE=16;
-static const int DEFAULT_HTTP_TIMEOUT=30;
+static const int DEFAULT_HTTP_SERVER_TIMEOUT=30;
 
 struct evhttp_request;
 struct event_base;

src/init.cpp

@@ -440,7 +440,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-rpcthreads=<n>", strprintf(_("Set the number of threads to service RPC calls (default: %d)"), DEFAULT_HTTP_THREADS));
     if (showDebug) {
         strUsage += HelpMessageOpt("-rpcworkqueue=<n>", strprintf("Set the depth of the work queue to service RPC calls (default: %d)", DEFAULT_HTTP_WORKQUEUE));
-        strUsage += HelpMessageOpt("-rpctimeout=<n>", strprintf("Timeout during HTTP requests (default: %d)", DEFAULT_HTTP_TIMEOUT));
+        strUsage += HelpMessageOpt("-rpcservertimeout=<n>", strprintf("Timeout during HTTP requests (default: %d)", DEFAULT_HTTP_SERVER_TIMEOUT));
     }
 
     if (mode == HMM_BITCOIN_QT)