mirror of https://github.com/BOINC/boinc.git
48 lines
1.6 KiB
HTML
48 lines
1.6 KiB
HTML
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<h2>Core client: FSM structure</h2>
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<p>
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The core client can perform many activities
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(file transfers, computations, RPCs to scheduling servers)
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in parallel.
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To manage this parallelism, the core client is
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structures as a number of <b>finite-state machines</b> (FSM).
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For example, an HTTP transaction is represented by an FSM
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whose states might include:
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<ul>
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<li> Waiting for connection establishment.
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<li> Waiting to send request header.
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<li> Waiting to send send request body.
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<li> Waiting for reply header.
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<li> Waiting for reply body.
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<li> Finished.
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</ul>
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<p>
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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,
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and provides a <b>poll()</b> function for
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detecting and performing state transitions.
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These functions are nonblocking.
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<p>
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The core client uses the following FSM types:
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<ul>
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<li><b>NET_XFER</b> (container: <b>NET_XFER_SET</b>).
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Each instance represents a network connection,
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for which data is being transferred to/from memory or a disk file.
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The <b>poll()</b> function uses <b>select()</b>
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to manage the FSM without blocking.
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<li><b>HTTP_OP</b> (container: <b>HTTP_OP_SET</b>).
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Each instance represents an HTTP operation
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(GET, PUT or POST).
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<li><b>FILE_XFER</b> (container: <b>FILE_XFER_SET</b>).
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Each instance represents a file transfer (upload or download) in progress.
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<li><b>ACTIVE_TASK</b> (container: <b>ACTIVE_TASK_SET</b>).
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Each instance represents a running application.
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</ul>
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<p>
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An FSM may be implemented using other FSMs;
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for example, FILE_XFER is implemented using HTTP_OP,
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which in turn is implemented using NET_XFER.
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