master_watch.c

[詳解]

/*++
/* NAME
/*  master_watch 3
/* SUMMARY
/*  Postfix master - monitor main.cf changes
/* SYNOPSIS
/*  #include "master.h"
/*
/*  void    master_str_watch(str_watch_table)
/*  const MASTER_STR_WATCH *str_watch_table;
/*
/*  void    master_int_watch(int_watch_table)
/*  MASTER_INT_WATCH *int_watch_table;
/* DESCRIPTION
/*  The Postfix master daemon is a long-running process. After
/*  main.cf is changed, some parameter changes may require that
/*  master data structures be recomputed.
/*
/*  Unfortunately, some main.cf changes cannot be applied
/*  on-the-fly, either because they require killing off existing
/*  child processes and thus disrupt service, or because the
/*  necessary support for on-the-fly data structure update has
/*  not yet been implemented.  Such main.cf changes trigger a
/*  warning that they require that Postfix be stopped and
/*  restarted.
/*
/*  This module provides functions that monitor selected main.cf
/*  parameters for change. The operation of these functions is
/*  controlled by tables that specify the parameter name, the
/*  current parameter value, a historical parameter value,
/*  optional flags, and an optional notify call-back function.
/*
/*  master_str_watch() monitors string-valued parameters for
/*  change, and master_int_watch() does the same for integer-valued
/*  parameters. Note that master_int_watch() needs read-write
/*  access to its argument table, while master_str_watch() needs
/*  read-only access only.
/*
/*  The functions log a warning when a parameter value has
/*  changed after re-reading main.cf, but the parameter is not
/*  flagged in the MASTER_*_WATCH table as "updatable" with
/*  MASTER_WATCH_FLAG_UPDATABLE.
/*
/*  If the parameter has a notify call-back function, then the
/*  function is called after main.cf is read for the first time.
/*  If the parameter is flagged as "updatable", then the function
/*  is also called when the parameter value changes after
/*  re-reading main.cf.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <string.h>
#include <unistd.h>

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>

/* Application-specific. */

#include "master.h"

/* master_str_watch - watch string-valued parameters for change */

void    master_str_watch(const MASTER_STR_WATCH *str_watch_table)
{
    const MASTER_STR_WATCH *wp;

    for (wp = str_watch_table; wp->name != 0; wp++) {

    /*
     * Detect changes to monitored parameter values. If a change is
     * supported, we discard the backed up value and update it to the
     * current value later. Otherwise we complain.
     */
    if (wp->backup[0] != 0
        && strcmp(wp->backup[0], wp->value[0]) != 0) {
        if ((wp->flags & MASTER_WATCH_FLAG_UPDATABLE) == 0) {
        msg_warn("ignoring %s parameter value change", wp->name);
        msg_warn("old value: \"%s\", new value: \"%s\"",
             wp->backup[0], wp->value[0]);
        msg_warn("to change %s, stop and start Postfix", wp->name);
        } else {
        myfree(wp->backup[0]);
        wp->backup[0] = 0;
        }
    }

    /*
     * Initialize the backed up parameter value, or update it if this
     * parameter supports updates after initialization. Optionally 
     * notify the application that this parameter has changed.
     */
    if (wp->backup[0] == 0) {
        if (wp->notify != 0)
        wp->notify();
        wp->backup[0] = mystrdup(wp->value[0]);
    }
    }
}

/* master_int_watch - watch integer-valued parameters for change */

void    master_int_watch(MASTER_INT_WATCH *int_watch_table)
{
    MASTER_INT_WATCH *wp;

    for (wp = int_watch_table; wp->name != 0; wp++) {

    /*
     * Detect changes to monitored parameter values. If a change is
     * supported, we discard the backed up value and update it to the
     * current value later. Otherwise we complain.
     */
    if ((wp->flags & MASTER_WATCH_FLAG_ISSET) != 0
        && wp->backup != wp->value[0]) {
        if ((wp->flags & MASTER_WATCH_FLAG_UPDATABLE) == 0) {
        msg_warn("ignoring %s parameter value change", wp->name);
        msg_warn("old value: \"%d\", new value: \"%d\"",
             wp->backup, wp->value[0]);
        msg_warn("to change %s, stop and start Postfix", wp->name);
        } else {
        wp->flags &= ~MASTER_WATCH_FLAG_ISSET;
        }
    }

    /*
     * Initialize the backed up parameter value, or update if it this
     * parameter supports updates after initialization. Optionally 
     * notify the application that this parameter has changed.
     */
    if ((wp->flags & MASTER_WATCH_FLAG_ISSET) == 0) {
        if (wp->notify != 0)
        wp->notify();
        wp->flags |= MASTER_WATCH_FLAG_ISSET;
        wp->backup = wp->value[0];
    }
    }
}