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  <!ENTITY dhdate      "<date>October 21, 2009</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 2.1</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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