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<title>Proposal for Daemon Package</title>
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<h1>Proposal for <em>Daemon</em> Package</h1>
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<h3>(0) Rationale</h3>

    <P>
      Since 1994, the Java&trade; programming language evolved and became a
      valid tool to develop, other than applets and client applications,
      reliable and performant server applications. The major disadvantage of
      the Java&trade; platform is that still today the only portable way to
      start a Java&trade; application relies on a single point of entry: the
      <CODE><EM CLASS="key">public static void</EM> main(<EM CLASS="ref">String</EM>[])</CODE>
      method.
    </P>
    <P>
      Having a single-point of entry is a valid solution for client
      applications, where interactively a user can command to the application
      to quit (which can terminate the Virtual Machine process at calling the
      <CODE><EM CLASS="ref">System</EM>.exit(<EM CLASS="key">int</EM>)</CODE>
      method), but in those cases where the application is not interactive
      (server applications) there is currently no portable way to notify
      the Virtual Machine of its imminent shutdown.
    </P>
    <P>
      A server application written in Java might have to perform several tasks
      before being able to shut down the Virtual Machine process. For example
      in the case of a Servlet container, before the VM process is shut down,
      sessions might need to be serialized to disk, and web applications need
      to be destroyed.
    </P>
    <P>
      One common solution to this problem is to create (for example) a
      <CODE><EM CLASS="ref">ServerSocket</EM></CODE> and wait for a particular
      message to be issued. When the message is received, all operations
      required to shut down the server applications are performed and at the
      end the <CODE><EM CLASS="ref">System</EM>.exit</CODE> method is called
      to terminate the Virtual Machine process. This method, however, implies
      several disadvantages and risks: for example in case of a system-wide
      shutdown, it might happen that the Virtual Machine process will be shut
      down directly by the operating system, without notifying the running
      server application. Or, for example, if an attacker finds out what is
      the required message to send to the server, and discovers a way to send
      this message to the running server application, he can easily interrupt
      the operation of a server, bypassing all the security restrictions
      implemented in the operating system.
    </P>
    <P>
      Most multi-user operating systems already have a way in which server
      applications are started and stopped, under Unix based operating systems
      non-interactive server applications are called <em>daemons</em> and are
      controlled by the operating system with a set of specified
      <em>signals</em>. Under Windows such programs are called <em>services</em>
      and are controlled by appropriate calls to specific functions defined in
      the application binary, but although the ways of dealing with the problem
      are different, in both cases the operating system can notify a server
      application of its imminent shutdown, and the application has the
      ability to perform certain tasks before its process of execution is
      destroyed.
    </P>

<h3>(1) Scope of the Package</h3>

    <P>
      The scope of this specification is to define an API in line with the
      current Java&trade; Platform APIs to support an alternative invocation
      mechanism which could be used instead of the above mentioned
      <CODE><EM CLASS="key">public static void</EM> main(<EM CLASS="ref">String</EM>[])</CODE>
      method. This specification cover the behavior and life cycle of what
      we define as &quot;Java &trade; daemons&quot;, or, in other words,
      non-interactive Java&trade; applications.
    </P>
    <P>
      This specification does not cover how the container of a Java&trade;
      daemon must be implemented, or how to build a native liaison between
      the operating system and the <CODE><EM CLASS="ref">Daemon</EM></CODE>
      interface, but defines the relation between the operating system
      process and the <CODE><EM CLASS="ref">Daemon</EM></CODE> implementation
      life cycle. It should be trivial for implementors to build a native
      liaison and container for Java&trade; daemons.
    </P>
    <P>
      This specification, together with the related API documentation, can be
      used by software developers to build portable non-interactive applications
      based on the Java&trade; platform.
    </P>

<h3>(1.5) Interaction With Other Packages</h3>

<p><em>Daemon</em> relies only on standard JDK 1.2 (or later) APIs for
production deployment.  It utilizes the JUnit unit testing framework for
developing and executing unit tests, but this is of interest only to
developers of the component.  Daemon will be a dependency for
several existing components in the open source world.</p>

<p>No external configuration files are utilized.</p>


<h3>(2) Initial Source of the Package</h3>

<p>The original Java classes come from the Jakarta Tomcat 4.0 project.</p>

<p>The proposed package name for the new component is
<code>org.apache.commons.daemon</code>.</p>


<h3>(3)  Required Jakarta-Commons Resources</h3>

<ul>
<li>CVS Repository - New directory <code>daemon</code> in the
    <code>jakarta-commons</code> CVS repository.</li>
<li>Mailing List - Discussions will take place on the general
    <em>dev@commons.apache.org</em> mailing list.  To help
    list subscribers identify messages of interest, it is suggested that
    the message subject of messages about this component be prefixed with
    [Daemon].</li>
<li>Bugzilla - New component "Daemon" under the "Commons" product
    category, with appropriate version identifiers as needed.</li>
<li>Jyve FAQ - New category "commons-daemon" (when available).</li>
</ul>


<h3>(4) Initial Committers</h3>

<p>The initial committers on the Daemon component shall be:</p>
<ul>
<li>Jean-Frederic Clere</li>
<li>Pier Fumagalli</li>
<li>Remy Maucherat</li>


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