BUG#10950 Occational 'Error in mgm protocol parser' error on mysqld startup

Display the (more commonly accurate) message that the mgm server closed our connection
and that we'll retry connecting to it.


ndb/src/common/transporter/TransporterRegistry.cpp:
  Fix error message in case of mgm disconnecting before we finished asking it for dynamic ports
ndb/src/mgmapi/mgmapi.cpp:
  Only display a mgm protocol error in the case of the mgm server having disconnected.
  
  Change ndb_mgm_is_connected to actually poll the socket to see if it's still open.

ndb/src/common/transporter/TransporterRegistry.cpp

@@ -1284,11 +1284,17 @@ TransporterRegistry::start_clients_thread()
 		if (server_port)
 		  t->set_s_port(server_port);
 	      }
-	      else
+	      else if(ndb_mgm_is_connected(m_mgm_handle))
 	      {
 		ndbout_c("Failed to get dynamic port to connect to: %d", res);
 		ndb_mgm_disconnect(m_mgm_handle);
 	      }
+	      else
+	      {
+		ndbout_c("Management server closed connection early. "
+			 "It is probably being shut down (or has crashed). "
+			 "We will retry the connection.");
+	      }
 	    }
 	    /** else
 	     * We will not be able to get a new port unless

ndb/src/mgmapi/mgmapi.cpp

@@ -323,16 +323,22 @@ ndb_mgm_call(NdbMgmHandle handle, const ParserRow<ParserDummy> *command_reply,
 
   const Properties* p = parser.parse(ctx, session);
   if (p == NULL){
-    /**
-     * Print some info about why the parser returns NULL
-     */
-    ndbout << "Error in mgm protocol parser. "
-	   << "cmd: '" << cmd
-	   << "' status=" << (Uint32)ctx.m_status
-	   << ", curr=" << ctx.m_currentToken
+    if(!ndb_mgm_is_connected(handle)) {
+      return NULL;
+    }
+    else
+    {
+      /**
+       * Print some info about why the parser returns NULL
+       */
+      ndbout << "Error in mgm protocol parser. "
+	     << "cmd: '" << cmd
+	     << "' status=" << (Uint32)ctx.m_status
+	     << ", curr=" << ctx.m_currentToken
 	   << endl;
-    DBUG_PRINT("info",("parser.parse returned NULL"));
-  } 
+      DBUG_PRINT("info",("parser.parse returned NULL"));
+    }
+  }
 #ifdef MGMAPI_LOG
   else {
     /** 
@@ -350,8 +356,24 @@ ndb_mgm_call(NdbMgmHandle handle, const ParserRow<ParserDummy> *command_reply,
 extern "C"
 int ndb_mgm_is_connected(NdbMgmHandle handle)
 {
+  struct pollfd pfd[1];
+  int r;
+
   if(!handle)
     return 0;
+
+  if(handle->connected)
+  {
+    pfd[0].fd= handle->socket;
+    pfd[0].events= POLLHUP | POLLIN | POLLOUT | POLLNVAL;
+    pfd[0].revents= 0;
+    r= poll(pfd,1,0);
+    if(pfd[0].revents & POLLHUP)
+    {
+      handle->connected= 0;
+      NDB_CLOSE_SOCKET(handle->socket);
+    }
+  }
   return handle->connected;
 }