Protocol Documentation

Table of Contents

• middleware.proto
• Application
• ChildCfg
• Empty
• Middleware
• Scalar Value Types

middleware.proto

The middleware layer.

This simple middleware layer will allow to have a simple way to configure and define all the application interaction.

Indeed, to communicate applications need the destination adress. This could be achieved by settings in each application, all the addresses of all the applications though a configuration file.

However this would be very hard to maintain. So intead, this middleware layer will be for now a simple directory, in which, each application will be registered at start-up.

Every application will have a local copy of this directory, in order to synchronously get the address of any other application.

This approach is not really reliable, a more effective approach would be to have a consensuce algorithm as RAFT to register each application.

Application

Define on which address a given service is available.

Field	Type	Label	Description
name	string	optional	The unique application name. This application name should be unique though the whole platform.
address	string	optional	The service address for gRPC request.

ChildCfg

Define the mddleware children base settings.

Field	Type	Label	Description
masterAddr	string	optional	The master adress for gRPC request. If the master is not available the child will refuse to start.
childAddr	string	optional	The child address to expose gRPC services.

Empty

An empty structure for synchronous request.

Field	Type	Label	Description

Middleware

The middleware service is here to exchange application location.

On start up, each application should:

1. Register its application.
2. Fetch all the applications locations.
3. Listen for location updates.

Method Name	Request Type	Response Type	Description
registerApplication	Application	Empty	Register in the directory the application location.
fetchApplications	Empty	Application	Fetch all the currently known locations.
pushApplications	Application	Empty	Update application local directory by the master.

Scalar Value Types

.proto Type	Notes	C++ Type	Java Type	Python Type
double		double	double	float
float		float	float	float
int32	Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint32 instead.	int32	int	int
int64	Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint64 instead.	int64	long	int/long
uint32	Uses variable-length encoding.	uint32	int	int/long
uint64	Uses variable-length encoding.	uint64	long	int/long
sint32	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s.	int32	int	int
sint64	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s.	int64	long	int/long
fixed32	Always four bytes. More efficient than uint32 if values are often greater than 2^28.	uint32	int	int
fixed64	Always eight bytes. More efficient than uint64 if values are often greater than 2^56.	uint64	long	int/long
sfixed32	Always four bytes.	int32	int	int
sfixed64	Always eight bytes.	int64	long	int/long
bool		bool	boolean	boolean
string	A string must always contain UTF-8 encoded or 7-bit ASCII text.	string	String	str/unicode
bytes	May contain any arbitrary sequence of bytes.	string	ByteString	str