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ganeti-confd.sgml 3.24 KiB
<!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [

  <!-- Please adjust the date whenever revising the manpage. -->
  <!ENTITY dhdate      "<date>June 08, 2010</date>">
  <!-- SECTION should be 1-8, maybe w/ subsection other parameters are
       allowed: see man(7), man(1). -->
  <!ENTITY dhsection   "<manvolnum>8</manvolnum>">
  <!ENTITY dhucpackage "<refentrytitle>ganeti-confd</refentrytitle>">
  <!ENTITY dhpackage   "ganeti-confd">

  <!ENTITY debian      "<productname>Debian</productname>">
  <!ENTITY gnu         "<acronym>GNU</acronym>">
  <!ENTITY gpl         "&gnu; <acronym>GPL</acronym>">
  <!ENTITY footer SYSTEM "footer.sgml">
]>

<refentry>
  <refentryinfo>
    <copyright>
      <year>2009</year>
      <holder>Google Inc.</holder>
    </copyright>
    &dhdate;
  </refentryinfo>
  <refmeta>
    &dhucpackage;

    &dhsection;
    <refmiscinfo>Ganeti 2.2</refmiscinfo>
  </refmeta>
  <refnamediv>
    <refname>&dhpackage;</refname>

    <refpurpose>Ganeti conf daemon</refpurpose>
  </refnamediv>
  <refsynopsisdiv>
    <cmdsynopsis>
      <command>&dhpackage; </command>
      <arg>-f</arg>
      <arg>-d</arg>

    </cmdsynopsis>
  </refsynopsisdiv>
  <refsect1>
    <title>DESCRIPTION</title>

    <para>
      <command>&dhpackage;</command> is a daemon used to answer queries related
      to the configuration of a Ganeti cluster.
    </para>

    <para>
      For testing purposes, you can give the <option>-f</option>
      option and the program won't detach from the running terminal.
    </para>

    <para>
      Debug-level message can be activated by giving the
      <option>-d</option> option.
    </para>
    <refsect2>
      <title>ROLE</title>
      <para>
        The role of the conf daemon is to make sure we have a highly available
        and very fast way to query cluster configuration values. This daemon is
        automatically active on all master candidates, and so has no single
        point of failure. It communicates via UDP so each query can easily be
        sent to multiple servers, and it answers queries from a cached copy of
        the config it keeps in memory, so no disk access is required to get an
        answer.
      </para>

      <para>
        The config is reloaded from disk automatically when it changes, with a
        rate limit of once per second.
      </para>

      <para>
        If the conf daemon is stopped on all nodes, its clients won't be able
        to get query answers.
      </para>
    </refsect2>

    <refsect2>
      <title>COMMUNICATION PROTOCOL</title>
      <para>
        The confd protocol is an HMAC authenticated json-encoded custom format,
        over UDP. A client library is provided to make it easy to write
        software to query confd. More information can be found in the Ganeti
        2.1 design doc, and an example usage can be seen in the (external) NBMA
        daemon for Ganeti.
      </para>
    </refsect2>

  </refsect1>

  &footer;

</refentry>

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