2015-04-08 08:52:58 +00:00
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<title>Module machi_flu1</title>
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<div class="navbar"><a name="#navbar_top"></a><table width="100%" border="0" cellspacing="0" cellpadding="2" summary="navigation bar"><tr><td><a href="overview-summary.html" target="overviewFrame">Overview</a></td><td><a href="http://www.erlang.org/"><img src="erlang.png" align="right" border="0" alt="erlang logo"></a></td></tr></table></div>
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<h1>Module machi_flu1</h1>
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<ul class="index"><li><a href="#description">Description</a></li><li><a href="#index">Function Index</a></li><li><a href="#functions">Function Details</a></li></ul>The Machi FLU file server + file location sequencer.
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<h2><a name="description">Description</a></h2><p>The Machi FLU file server + file location sequencer.</p>
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<p>This module implements only the Machi FLU file server and its
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implicit sequencer.
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Please see the EDoc "Overview" for details about the FLU as a
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primitive file server process vs. the larger Machi design of a FLU
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as a sequencer + file server + chain manager group of processes.</p>
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2015-05-20 03:37:28 +00:00
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<p>The FLU is named after the CORFU server "FLU" or "FLash Unit" server.</p>
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<h4><a name="Protocol_origins">Protocol origins</a></h4>
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<p>The protocol implemented here is an artisanal, hand-crafted, silly
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thing that was very quick to put together for a "demo day" proof of
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concept. It will almost certainly be replaced with something else,
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both in terms of wire format and better code separation of
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serialization/deserialization vs. network transport management,
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etc.</p>
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<p>For the moment, this module implements a rudimentary TCP-based
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protocol as the sole supported access method to the server,
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sequencer, and projection store. Conceptually, those three
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services are independent and ought to have their own protocols. As
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a practical matter, there is no need for wire protocol
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compatibility. Furthermore, from the perspective of failure
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detection, it is very convenient that all three FLU-related
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services are accessed using the same single TCP port.</p>
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2015-05-20 03:37:28 +00:00
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<h4><a name="TODO_items">TODO items</a></h4>
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2015-05-20 02:14:55 +00:00
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<p>TODO There is a major missing feature in this FLU implementation:
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there is no "write-once" enforcement for any position in a Machi
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file. At the moment, we rely on correct behavior of the client
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& the sequencer to avoid overwriting data. In the Real World,
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however, all Machi file data is supposed to be exactly write-once
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to avoid problems with bugs, wire protocol corruption, malicious
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clients, etc.</p>
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<p>TODO The per-file metadata tuple store is missing from this implementation.</p>
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<p>TODO Section 4.1 ("The FLU") of the Machi design doc suggests that
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the FLU keep track of the epoch number of the last file write (and
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perhaps last metadata write), as an optimization for inter-FLU data
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replication/chain repair.</p>
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TODO Section 4.2 ("The Sequencer") says that the sequencer must
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change its file assignments to new & unique names whenever we move
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to wedge state. This is not yet implemented. In the current
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Erlang process scheme (which will probably be changing soon), a
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simple implementation would stop all existing processes that are
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running run_seq_append_server().
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<h2><a name="index">Function Index</a></h2>
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<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#make_listener_regname-1">make_listener_regname/1</a></td><td></td></tr>
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<tr><td valign="top"><a href="#make_projection_server_regname-1">make_projection_server_regname/1</a></td><td></td></tr>
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<tr><td valign="top"><a href="#start_link-1">start_link/1</a></td><td></td></tr>
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<tr><td valign="top"><a href="#stop-1">stop/1</a></td><td></td></tr>
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<tr><td valign="top"><a href="#update_wedge_state-3">update_wedge_state/3</a></td><td></td></tr>
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</table>
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<h2><a name="functions">Function Details</a></h2>
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2015-05-20 02:14:55 +00:00
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<h3 class="function"><a name="make_listener_regname-1">make_listener_regname/1</a></h3>
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<div class="spec">
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<p><tt>make_listener_regname(BaseName) -> any()</tt></p>
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</div>
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<h3 class="function"><a name="make_projection_server_regname-1">make_projection_server_regname/1</a></h3>
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<div class="spec">
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<p><tt>make_projection_server_regname(BaseName) -> any()</tt></p>
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</div>
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2015-04-08 08:52:58 +00:00
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<h3 class="function"><a name="start_link-1">start_link/1</a></h3>
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<div class="spec">
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<p><tt>start_link(Rest) -> any()</tt></p>
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</div>
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<h3 class="function"><a name="stop-1">stop/1</a></h3>
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<div class="spec">
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<p><tt>stop(Pid) -> any()</tt></p>
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</div>
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2015-05-20 02:14:55 +00:00
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<h3 class="function"><a name="update_wedge_state-3">update_wedge_state/3</a></h3>
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<div class="spec">
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<p><tt>update_wedge_state(PidSpec, Boolean, EpochId) -> any()</tt></p>
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</div>
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2015-04-08 08:52:58 +00:00
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<hr>
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<div class="navbar"><a name="#navbar_bottom"></a><table width="100%" border="0" cellspacing="0" cellpadding="2" summary="navigation bar"><tr><td><a href="overview-summary.html" target="overviewFrame">Overview</a></td><td><a href="http://www.erlang.org/"><img src="erlang.png" align="right" border="0" alt="erlang logo"></a></td></tr></table></div>
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2015-05-20 03:51:25 +00:00
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<p><i>Generated by EDoc, May 20 2015, 12:50:53.</i></p>
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2015-04-08 08:52:58 +00:00
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