<component>

  <!-- Note on logging configuration:

       This schema component expects to use a section type named
       "eventlog"; this type needs to be provided by some other
       component that the top-level schema needs to import.

       The import is not performed here to allow applications to
       load the type from different components.
    -->

  <sectiontype name="runner">

    <description>
      This section describes the options for zdctl.py and zdrun.py.
      The only required option is "program".  Many other options have
      no default value specified in the schema; in some cases, the
      program calculates a dynamic default, in others, the feature
      associated with the option is disabled.

      For those options that also have corresponding command-line
      options, the command line option (short and long form) are given
      here too.
    </description>

    <section name="*" type="ZConfig.logger.log"
             attribute="eventlog"
             required="no">
      <description>
        Log configuration for zdctl.py and zdrun.py.  These
        applications will normally use the eventlog section at the top
        level of the configuration, but will use this eventlog section
        if it exists.

        (This is done so that the combined schema for the runner and
        the controlled application will write to the same logs by
        default, but a separation of logs can be achieved if desired.)
      </description>
    </section>

    <key name="program" datatype="string-list"
         required="yes">
      <description>
        Command-line option: -p or --program (zdctl.py only).

        This option gives the command used to start the subprocess
        managed by zdrun.py.  This is currently a simple list of
        whitespace-delimited words. The first word is the program
        file, subsequent words are its command line arguments.  If the
        program file contains no slashes, it is searched using $PATH.
        (XXX There is no way to to include whitespace in the program
        file or an argument, and under certain circumstances other
        shell metacharacters are also a problem, e.g. the "foreground"
        command of zdctl.py.)

        NOTE: zdrun.py doesn't use this option; it uses its positional
        arguments.  Rather, zdctl.py uses this option to determine the
        positional argument with which to invoke zdrun.py.  (XXX This
        could be better.)
      </description>
    </key>

    <key name="python" datatype="existing-path"
         required="no">
      <description>
        Path to the Python interpreter.  Used by zdctl.py to start the
        zdrun.py process.  Defaults to sys.executable.
      </description>
    </key>

    <key name="zdrun" datatype="existing-path"
         required="no">
      <description>
        Path to the zdrun.py script.  Used by zdctl.py to start the
        zdrun.py process.  Defaults to a file named "zdrun.py" in the
        same directory as zdctl.py.
      </description>
    </key>

    <key name="socket-name" datatype="existing-dirpath"
         required="no"
         default="zdsock">
      <description>
        Command-line option: -s or --socket-name.

        The pathname of the Unix domain socket used for communication
        between zdctl.py and zdrun.py.  The default is relative to the
        current directory in which zdctl.py and zdrun.py are started.
        You want to specify an absolute pathname here.
      </description>
    </key>

    <key name="daemon" datatype="boolean"
         required="no"
         default="false">
      <description>
        Command-line option: -d or --daemon.

        If this option is true, zdrun.py runs in the background as a
        true daemon.  It forks a child process which becomes the
        subprocess manager, while the parent exits (making the shell
        that started it believe it is done).  The child process also
        does the following:

        - if the directory option is set, change into that directory

        - redirect stdin, stdout and stderr to /dev/null

        - call setsid() so it becomes a session leader

        - call umask() with specified value
      </description>
    </key>

    <key name="directory" datatype="existing-directory"
         required="no">
      <description>
        Command-line option: -z or --directory.

        If the daemon option is true, this option can specify a
        directory into which zdrun.py changes as part of the
        "daemonizing".  If the daemon option is false, this option is
        ignored.
      </description>
    </key>

    <key name="backoff-limit" datatype="integer"
         required="no"
         default="10">
      <description>
        Command-line option: -b or --backoff-limit.

        When the subprocess crashes, zdrun.py inserts a one-second
        delay before it restarts it.  When the subprocess crashes
        again right away, the delay is incremented by one second, and
        so on.  What happens when the delay has reached the value of
        backoff-limit (in seconds), depends on the value of the
        forever option.  If forever is false, zdrun.py gives up at
        this point, and exits.  An always-crashing subprocess will
        have been restarted exactly backoff-limit times in this case.
        If forever is true, zdrun.py continues to attempt to restart
        the process, keeping the delay at backoff-limit seconds.

        If the subprocess stays up for more than backoff-limit
        seconds, the delay is reset to 1 second.
      </description>
    </key>

    <key name="forever" datatype="boolean"
         required="no"
         default="false">
      <description>
        Command-line option: -f or --forever.

        If this option is true, zdrun.py will keep restarting a
        crashing subprocess forever.  If it is false, it will give up
        after backoff-limit crashes in a row.  See the description of
        backoff-limit for details.
      </description>
    </key>

    <key name="exit-codes" datatype="zdaemon.zdoptions.list_of_ints"
         required="no"
         default="0,2">
      <description>
        Command-line option: -x or --exit-codes.

        If the subprocess exits with an exit status that is equal to
        one of the integers in this list, zdrun.py will not restart
        it.  The default list requires some explanation.  Exit status
        0 is considered a willful successful exit; the ZEO and Zope
        server processes use this exit status when they want to stop
        without being restarted.  (Including in response to a
        SIGTERM.)  Exit status 2 is typically issued for command line
        syntax errors; in this case, restarting the program will not
        help!

        NOTE: this mechanism overrides the backoff-limit and forever
        options; i.e. even if forever is true, a subprocess exit
        status code in this list makes zdrun.py give up.  To disable
        this, change the value to an empty list.
      </description>
    </key>

    <key name="user" datatype="string"
         required="no">
      <description>
        Command-line option: -u or --user.

        When zdrun.py is started by root, this option specifies the
        user as who the the zdrun.py process (and hence the daemon
        subprocess) will run.  This can be a user name or a numeric
        user id.  Both the user and the group are set from the
        corresponding password entry, using setuid() and setgid().
        This is done before zdrun.py does anything else besides
        parsing its command line arguments.

        NOTE: when zdrun.py is not started by root, specifying this
        option is an error.  (XXX This may be a mistake.)

        XXX The zdrun.py event log file may be opened *before*
        setuid() is called.  Is this good or bad?
      </description>
    </key>

    <key name="umask" datatype="zdaemon.zdoptions.octal_type"
         required="no"
         default="022">
      <description>
        Command-line option: -m or --umask.

        When daemon mode is used, this option specifies the octal umask
        of the subprocess.
      </description>
    </key>

    <key name="hang-around" datatype="boolean"
         required="no"
         default="false">
      <description>
        If this option is true, the zdrun.py process will remain even
        when the daemon subprocess is stopped.  In this case, zdctl.py
        will restart zdrun.py as necessary.  If this option is false,
        zdrun.py will exit when the daemon subprocess is stopped
        (unless zdrun.py intends to restart it).
      </description>
    </key>

    <key name="default-to-interactive" datatype="boolean"
         required="no"
         default="true">
      <description>
        If this option is true, zdctl.py enters interactive mode
        when it is invoked without a positional command argument.  If
        it is false, you must use the -i or --interactive command line
        option to zdctl.py to enter interactive mode.
      </description>
    </key>

    <key name="logfile" datatype="existing-dirpath"
         required="no">
      <description>
        This option specifies a log file that is the default target of
        the "logtail" zdctl.py command.

        NOTE: This is NOT the log file to which zdrun.py writes its
        logging messages!  That log file is specified by the
        &lt;eventlog&gt; section.
      </description>
    </key>

    <key name="prompt" datatype="string"
         required="no" default="zdctl>">
       <description>
         The prompt shown by the controller program.
       </description>
    </key>

  </sectiontype>

</component>
