Refactor handling of exceptions in protocol server command executors.

Add a standard method to Replyable that will be called if a recoverable
exception (a BoxException) occurs, and can return a protocol Message to be
sent to the client, such as an error code for various standard errors, or
rethrow the exception.

If you want something different, catch exceptions and return the desired
reply yourself, or you'll get the default handling.

1 files changed, 36 insertions, 15 deletions

diff --git a/lib/server/makeprotocol.pl.in b/lib/server/makeprotocol.pl.in
index 65d1f3a9..d61a14d0 100755
--- a/lib/server/makeprotocol.pl.in
+++ b/lib/server/makeprotocol.pl.in
@@ -604,10 +604,11 @@ public:
 
 	virtual int GetTimeout() = 0;
 	void SendStreamAfterCommand(std::auto_ptr<IOStream> apStream);
-	
+
 protected:
 	std::list<IOStream*> mStreamsToSend;
 	void DeleteStreamsToSend();
+	virtual std::auto_ptr<$message_base_class> HandleException(BoxException& e) const;
 
 private:
 	$replyable_base_class(const $replyable_base_class &rToCopy); /* do not call */
@@ -1077,24 +1078,31 @@ void $server_or_client_class\::DoServer($context_class &rContext)
 		// Run the command
 		try
 		{
-			if(pobj->HasStreamWithCommand())
+			try
 			{
-				std::auto_ptr<IOStream> apDataStream = ReceiveStream();
-				SelfFlushingStream autoflush(*apDataStream);
-				preply = pobj->DoCommand(*this, rContext, *apDataStream);
+				if(pobj->HasStreamWithCommand())
+				{
+					std::auto_ptr<IOStream> apDataStream = ReceiveStream();
+					SelfFlushingStream autoflush(*apDataStream);
+					preply = pobj->DoCommand(*this, rContext, *apDataStream);
+				}
+				else
+				{
+					preply = pobj->DoCommand(*this, rContext);
+				}
 			}
-			else
+			catch(BoxException &e)
 			{
-				preply = pobj->DoCommand(*this, rContext);
+				// First try a the built-in exception handler
+				preply = HandleException(e);
 			}
 		}
-		catch (std::exception &e)
-		{
-			Send($cmd_classes{$error_message}());
-			throw;
-		}
 		catch (...)
 		{
+			// Fallback in case the exception isn't a BoxException
+			// or the exception handler fails as well. This path
+			// throws the exception upwards, killing the process
+			// that handles the current client.
 			Send($cmd_classes{$error_message}());
 			throw;
 		}
@@ -1183,19 +1191,32 @@ __E
 				}
 				elsif($writing_local)
 				{
+					print CPP <<__E;
+	std::auto_ptr<$message_base_class> apReply;
+	try
+	{
+__E
 					if($has_stream)
 					{
 						print CPP <<__E;
-	std::auto_ptr<$message_base_class> apReply = rQuery.DoCommand(*this,
-		mrContext, *apDataStream);
+		apReply = rQuery.DoCommand(*this, mrContext, *apDataStream);
 __E
 					}
 					else
 					{
 						print CPP <<__E;
-	std::auto_ptr<$message_base_class> apReply = rQuery.DoCommand(*this, mrContext);
+		apReply = rQuery.DoCommand(*this, mrContext);
 __E
 					}
+
+					print CPP <<__E;
+	}
+	catch(BoxException &e)
+	{
+		// First try a the built-in exception handler
+		apReply = HandleException(e);
+	}
+__E
 				}
 
 				# Common to both client and local