Metadata-Version: 1.1
Name: messi
Version: 0.9.0
Summary: Reliable message passing in distributed systems.
Home-page: https://github.com/eerimoq/messi
Author: Erik Moqvist
Author-email: erik.moqvist@gmail.com
License: MIT
Description: |buildstatus|_
        |coverage|_
        |codecov|_
        |nala|_
        
        ⚽ Messi
        ========
        
        Reliable message passing for distributed systems.
        
        - `C` source code generator.
        
        Known limitations:
        
        - The connection is immediately dropped if ``write()`` does not accept
          exaxtly given amount of bytes. Buffering of remaining data may be
          added at some point.
        
        Project homepage: https://github.com/eerimoq/messi
        
        Installation
        ------------
        
        .. code-block:: python
        
           $ pip install messi
        
        Architecture
        ------------
        
        A `Messi` system consists of servers and clients. Once a client has
        successfully connected to a server, messages defined in their protocol
        specification can be reliably sent between them.
        
        `Messi` guarantees that all sent messages are delivered in order to
        the peer. However, just as for TCP, any data/messages in flight when
        the connection is lost will likely be lost.
        
        Below is a sequence diagram showing typical communication between a
        server and a client. The messages ``FooReq``, ``FooRsp``, ``BarInd``,
        ``FieReq`` and ``FieRsp`` are defined in the protocol ``my_protocol``,
        which is defined later in this document.
        
        .. code-block:: text
        
                         +--------+                               +--------+
                         | client |                               | server |
                         +--------+                               +--------+
                             |             1. TCP connect              |
                             |========================================>|
              on_connected() |                2. ping                  | on_client_connected()
                             |---------------------------------------->|
                             |                   pong                  |
                             |<----------------------------------------|
                      send() |               3. FooReq                 |
                             |========================================>|
                             |                  FooRsp                 | reply()
                             |<========================================|
                      send() |               4. BarInd                 |
                             |========================================>|
                      send() |                  BarInd                 |
                             |========================================>|
                             |               5. FieReq                 | send()
                             |<========================================|
                      send() |                  FieRsp                 |
                             |========================================>|
                             .                                         .
                             .                                         .
                             .                                         .
                             |                6. ping                  |
                             |---------------------------------------->|
                             .                                         .
           on_disconnected() .                                         . on_client_disconnected()
                             .                                         .
        
           Legend:
        
             ---: Background communication. No user interaction needed.
        
             ===: User initiated communication.
        
        1. The client connects to the server. on_connected() and
           on_client_connected() are called to notify the user that the
           connection has been established.
        
        2. The client sends a ping message to the server, which responds with
           a pong message. This is done in the background. No user interaction
           needed.
        
        3. The client sends ``FooReq`` to the server, which responds with
           ``FooRsp``.
        
        4. The client sends ``BarInd`` twice to the server. No response is
           defined.
        
        5. The server sends ``FieReq`` to the client, which responds with
           ``FieRsp``.
        
        6. The client sends another ping message. This time the server does
           not respond. on_disconnected() and on_client_disconnected() are
           called to notify the user about the disconnection.
        
        Messi protocol specification
        ----------------------------
        
        All messages sent on the wire consists of a type, a size and optional
        payload. This enables both streaming and packet based transport
        protocols. The transport protocol must be reliable (guaranteed in
        order delivery).
        
        Type and size are in network byte order (big endian).
        
        .. code-block:: text
        
           +---------+---------+-----------------+
           | 4b type | 4b size | <size>b payload |
           +---------+---------+-----------------+
        
           TYPE  SIZE  DESCRIPTION
           ------------------------------------------------------------------
              1     n  Client to server user message (client --> server).
        
                       Encoded "message ClientToServer" messages.
        
              2     n  Server to client user message (server --> client).
        
                       Encoded "message ServerToClient" messages.
        
              3     0  Ping message (client --> server).
              4     0  Pong message (server --> client).
        
        User messages
        ^^^^^^^^^^^^^
        
        User messages are defined in Googles `Protocol Buffers`_ language
        version 3.
        
        Here is an example defining a protocol called ``my_protocol``. The two
        messages ``ClientToServer`` and ``ServerToClient`` must be present in
        every protocol specification. ``ClientToServer`` contains all messages
        sent from clients to servers, and ``ServerToClient`` contains all
        messages sent from servers to clients.
        
        .. code-block:: protobuf
        
           syntax = "proto3";
        
           // The protocol name.
           package my_protocol;
        
           // Messages sent from client to server.
           message ClientToServer {
               oneof messages {
                   FooReq foo_req = 1;
                   BarInd bar_ind = 2;
                   FieRsp fie_rsp = 3;
               }
           }
        
           // Messages sent from server to client.
           message ServerToClient {
               oneof messages {
                   FooRsp foo_rsp = 1;
                   FieReq fie_req = 2;
               }
           }
        
           // Message definitions.
           message FooReq {
           }
        
           message FooRsp {
           }
        
           message BarInd {
           }
        
           message FieReq {
           }
        
           message FieRsp {
           }
        
        Ping and pong messages
        ^^^^^^^^^^^^^^^^^^^^^^
        
        A client pings its server periodically. A client will close the
        connection and report an error if the server does not answer with pong
        within given time. Likewise, the server will close the connection and
        report an error if it does not receive ping within given time.
        
        The ping-pong mechanism is only used if the transport layer does not
        provide equivalent functionality.
        
        Error handling
        --------------
        
        `Messi` aims to minimize the amount of error handling code in the user
        application. Almost all functions always succeeds from the caller
        point of view. For example, ``PROTO_client_send()`` returns
        ``void``. If an error occurs, likely a connection issue, the
        disconnect callback is called to notify the user that the connection
        was dropped.
        
        C source code
        -------------
        
        Generate server and client side C source code.
        
        .. code-block:: text
        
           $ messi generate_c_source examples/chat/chat.proto
        
        Use ``-p/--platform`` to select which platform to generate code
        for.
        
        Supported platforms:
        
        - Linux TCP, using `epoll`_ and `timerfd`_.
        
        Planned platforms:
        
        - `async`_.
        
        The generated code is **not** thread safe.
        
        Client side
        ^^^^^^^^^^^
        
        Per client.
        
        .. code-block:: c
        
           void PROTO_client_init();   // Initialize given client.
           void PROTO_client_start();  // Connect to the server. The connected callback is
                                       // called once connected. Automatic reconnect if
                                       // disconnected.
           void PROTO_client_stop();   // Disconnect from the server. Call start to connect
                                       // again.
           void PROTO_client_send();   // Send prepared message to the server.
        
           typedef void (*PROTO_client_on_connected_t)();    // Callback called when connected
                                                             // to the server.
           typedef void (*PROTO_client_on_disconnected_t)(); // Callback called when disconnected
                                                             // from the server.
        
        Per Linux client.
        
        .. code-block:: c
        
           void PROTO_client_process();  // Process all pending events on given file
                                         // descriptor (if it belongs to given client).
        
        Per message.
        
        .. code-block:: c
        
           void PROTO_client_init_MESSAGE(); // Prepare given message. Call send or reply to
                                             // send it.
        
           typedef void (*PROTO_client_on_MESSAGE_t)(); // Callback called when given message
                                                        // is received from the server.
        
        Server side
        ^^^^^^^^^^^
        
        Per server.
        
        .. code-block:: c
        
           void PROTO_server_init();        // Initialize given server.
           void PROTO_server_start();       // Start accepting clients.
           void PROTO_server_stop();        // Disconnect any clients and stop accepting new
                                            // clients.
           void PROTO_server_send();        // Send prepared message to given client.
           void PROTO_server_reply();       // Send prepared message to current client.
           void PROTO_server_broadcast();   // Send prepared message to all clients.
           void PROTO_server_disconnect();  // Disconnect current or given client.
        
           typedef void (*PROTO_server_on_client_connected_t)();    // Callback called when a
                                                                    // client has connected.
           typedef void (*PROTO_server_on_client_disconnected_t)(); // Callback called when a
                                                                    // client is disconnected.
        
        Per Linux server.
        
        .. code-block:: c
        
           void PROTO_server_process();  // Process all pending events on given file
                                         // descriptor (if it belongs to given server).
        
        Per message.
        
        .. code-block:: c
        
           void PROTO_server_init_MESSAGE(); // Prepare given message. Call send, reply or
                                             // broadcast to send it.
        
           typedef void (*PROTO_server_on_MESSAGE_t)(); // Callback called when given message
                                                        // is received from given client.
        
        .. |buildstatus| image:: https://travis-ci.com/eerimoq/messi.svg?branch=master
        .. _buildstatus: https://travis-ci.com/eerimoq/messi
        
        .. |coverage| image:: https://coveralls.io/repos/github/eerimoq/messi/badge.svg?branch=master
        .. _coverage: https://coveralls.io/github/eerimoq/messi
        
        .. |codecov| image:: https://codecov.io/gh/eerimoq/messi/branch/master/graph/badge.svg
        .. _codecov: https://codecov.io/gh/eerimoq/messi
        
        .. |nala| image:: https://img.shields.io/badge/nala-test-blue.svg
        .. _nala: https://github.com/eerimoq/nala
        
        .. _epoll: https://en.wikipedia.org/wiki/Epoll
        
        .. _timerfd: http://man7.org/linux/man-pages/man2/timerfd_settime.2.html
        
        .. _async: https://github.com/eerimoq/async
        
        .. _Protocol Buffers: https://developers.google.com/protocol-buffers/docs/proto3
        
Platform: UNKNOWN
Classifier: License :: OSI Approved :: MIT License
Classifier: Programming Language :: Python :: 3
