95 lines
5.2 KiB
Ada
95 lines
5.2 KiB
Ada
-------------------------------------------------------------------------------
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-- --
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-- 0MQ Ada-binding --
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-- --
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-- Z M Q . P R O X Y S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 2013-2020, per.s.sandberg@bahnhof.se --
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-- --
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-- Permission is hereby granted, free of charge, to any person obtaining a --
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-- copy of this software and associated documentation files --
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-- (the "Software"), to deal in the Software without restriction, including --
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-- without limitation the rights to use, copy, modify, merge, publish, --
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-- distribute, sublicense, and / or sell copies of the Software, and to --
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-- permit persons to whom the Software is furnished to do so, subject to --
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-- the following conditions : --
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-- --
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-- The above copyright notice and this permission notice shall be included --
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-- in all copies or substantial portions of the Software. --
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-- --
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-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS --
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-- OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF --
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-- MERCHANTABILITY, --
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-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL --
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-- THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR --
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-- OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, --
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-- ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR --
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-- OTHER DEALINGS IN THE SOFTWARE. --
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-------------------------------------------------------------------------------
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-------------------------------------------------------------------------------
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-- Proxys are building blocks intended to serve as intermediate nodes
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-- in complex messaging topologies.
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--
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-- Example usage
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-- Shared queue
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-- When the frontend is a ROUTER socket, and the backend is a DEALER socket,
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-- the proxy shall act as a shared queue that collects requests from a set
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-- of clients, and distributes these fairly among a set ofservices.
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-- Requests shall be fair-queued from frontend connections and distributed
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-- evenly across backend connections.
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-- Replies shall automatically return to the client that made the original
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-- request.
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-- Forwarder
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-- When the frontend is a XSUB socket, and the backend is a XPUB socket,
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-- the proxy shall act as a message forwarder that collects messages from a
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-- set of publishers and forwards these to a set of subscribers. This may be
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-- used to bridge networks transports, e.g.
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-- read on tcp:// and forward on pgm://.
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-- Streamer
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-- When the frontend is a PULL socket, and the backend is a PUSH socket,
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-- the proxy shall collect tasks from a set of clients and forwards these
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-- to a set of workers using the pipeline pattern
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--
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-- Example:
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-- Create frontend and backend sockets
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-- declare
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-- context : ZMQ.Contexts.Context;
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-- frontend : ZMQ.Sockets.Socket;
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-- backend : ZMQ.Sockets.Socket;
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-- begin
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-- frontend.Initialize(context, ZMQ.Sockets.Router);
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-- frontend.bind("tcp://*:5555");
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-- backend.Initialize(context, ZMQ.Sockets.Dealer);
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-- backend.bind ("tcp://*:5556");
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-- ZMQ.Proxys.Proxy(frontend,backend);
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-- end;
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-------------------------------------------------------------------------------
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with ZMQ.Sockets;
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package ZMQ.Proxys is
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procedure Proxy
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(Frontend : not null access Sockets.Socket;
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Backend : not null access Sockets.Socket;
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Capture : access Sockets.Socket := null);
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-- starts the built-in <20>MQ proxy in the current application thread.
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-- The proxy connects a frontend socket to a backend socket.S
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-- Conceptually, data flows from frontend to backend.
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-- Depending on the socket types, replies may flow in the opposite
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-- direction. The direction is conceptual only;
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-- the proxy is fully symmetric and there is no technical difference
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-- between frontend and backend.
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-- Before calling Initialize you must set any socket options,
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-- and connect or bind both frontend and backend sockets.
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-- The two conventional proxy models are:
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-- The proxy runs in the current thread and returns only if/when the
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-- current context is closed.
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-- If the capture socket is not NULL, the proxy shall send all messages,
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-- received on both frontend and backend, to the capture socket.
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-- The capture socket should be a PUB, DEALER, PUSH, or PAIR socket.
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end ZMQ.Proxys;
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