2002-07-29 19:01:38 +00:00
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<html lang="en">
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<head>
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<title>Core Client: Finite-State Machine (FSM) Structure</title>
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<meta name="generator" content="BBEdit 6.1.2">
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</head>
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<body>
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<h2>Core Client: Finite-State Machine (FSM) Structure</h2>
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2002-04-30 22:22:54 +00:00
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<p>
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2002-07-29 19:01:38 +00:00
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The core client can perform many activities (file transfers,
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computations, RPCs to scheduling servers) in parallel. To manage this
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parallelism, the core client is structures as a number of
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<b>finite-state machines</b> (FSM). For example, an HTTP transaction is
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represented by an FSM whose states might include:
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</p>
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<ul>
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<li>
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Waiting for connection establishment.
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</li>
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<li>
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Waiting to send request header.
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</li>
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<li>
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Waiting to send send request body.
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</li>
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<li>
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Waiting for reply header.
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</li>
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<li>
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Waiting for reply body.
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</li>
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<li>
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Finished.
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</li>
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2002-04-30 22:22:54 +00:00
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</ul>
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<p>
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2002-07-29 19:01:38 +00:00
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FSMs of a particular type are managed by an <b>FSM container</b>.
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Each FSM container manages a set of FSMs, and provides a <b>poll()</b>
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function for detecting and performing state transitions. These functions
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are nonblocking.
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</p>
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<p>
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2002-07-29 19:01:38 +00:00
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The core client uses the following FSM types:
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</p>
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<ul>
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2002-07-29 19:01:38 +00:00
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<li>
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<b>NET_XFER</b> (container: <b>NET_XFER_SET</b>). Each instance
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represents a network connection, for which data is being transferred
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to/from memory or a disk file. The <b>poll()</b> function uses
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<b>select()</b> to manage the FSM without blocking.
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</li>
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<li>
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<b>HTTP_OP</b> (container: <b>HTTP_OP_SET</b>). Each instance
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represents an HTTP operation (GET, PUT or POST).
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</li>
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<li>
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<b>FILE_XFER</b> (container: <b>FILE_XFER_SET</b>). Each
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instance represents a file transfer (upload or download) in progress.
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</li>
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<li>
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<b>ACTIVE_TASK</b> (container: <b>ACTIVE_TASK_SET</b>). Each
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instance represents a running application.
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</li>
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2002-04-30 22:22:54 +00:00
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</ul>
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<p>
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2002-07-29 19:01:38 +00:00
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An FSM may be implemented using other FSMs; for example, FILE_XFER
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is implemented using HTTP_OP, which in turn is implemented using
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NET_XFER.
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</p>
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</body>
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</html>
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