Argon ===== Note: Argon is still under active development. Most features are complete, but it is still being tested for robustness. Argon is a platform for distributed services written in Modern Perl. Its goals are: * Simple design of distributed systems * Task prioritization * Uniformity of worker nodes * Bounded queues * Robust design Simple design of distributed systems ------------------------------------ Argon applications are built from simple components. The most basic piece is an Argon::Node, which manages a configurable pool of local Perl processes. Acting alone, a node can listen on a TCP/IP socket and accept new tasks. Multiple nodes work in tandem through an Argon::Cluster. Clusters maintain a pool of nodes, routing tasks to the most available node based on it's recent performance and current load. Tasks are assigned by passing a class name and arguments to an instance of an Argon::Client. Because all components of the system use the same protocol, it does not matter whether a client connects to a node or a cluster. Tasks are sent to the specified entry point to the Argon application and routed appropriately. The client's caller is suspended (using Coro) until the task is successfully completed. Task prioritization --------------------- Tasks are prioritized and the most important tasks are pushed to the front of the line. In cases of high load, the system will reject tasks which it cannot handle. The client accounts for this transparently, rescheduling the task to be handled after the system again becomes available. Clusters actively track task delivery and route incoming tasks to the most available node. Uniformity of worker nodes -------------------------- With many systems currently available, individual worker processes handle a specific type of task. To increase a task's priority, more worker processes are launched and configured to query a specific job queue. Argon worker processes are controlled by a node as a pool. Any worker may handle any type of task. This way, no worker processes remain idle, allowing another, busier worker's queue to grow. This prevents backlogs and keeps the system more responsive. Bounded queues -------------- Task queues are bounded. By enforcing a cap on the number of tasks that may be queued, the application is protected from DOS-like attacks and remains responsive at all times. This prevents queues from growing so large that a spike in traffic causes a secondary delay in restoring responsiveness as the backlog of tasks are first cleared. Tasks that cannot be added due to queue constraints are rejected and the client software is notified. Client software will automatically and transparently retry tasks that have been rejected. Robust design ------------- Argon is designed to ensure that all parts of the system function independently of the other parts. Nodes do not crash if their supervising cluster becomes unavailable and vice versa; clusters will continue to route to any available nodes until a disconnected node comes back online. New nodes may be added to the system without restarting the cluster. This allows an application administrator to seamlessly boost performance without interrupting service for existing clients. Usage ===== See `/bin` for examples of usage. LICENSE AND COPYRIGHT ===================== Copyright (C) 2013 "Jeff Ober" This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License. See for more information.