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mmstatd包含一个 C库和服务器

$Id: README,v 1.2 2003/01/01 14:54:11 mmondor Exp $



MMSTATD(8)              NetBSD System Manager's Manual              MMSTATD(8)

NAME
     mmstatd - Statistics librarian and logger daemon with recovery and trans-
     action support

SYNOPSIS
     mmstatd [config_file]

DESCRIPTION
     mmstatd consists of a statistics librarian daemon used by the familly of
     mm utilities (mmmail, mmftpd, etc). It simply allows applications to
     record statistical information using a key-based system. It also supports
     transactions and crash recovery logging. Moreover, it features volatile
     and consistant database entries, with creation and modification times-
     tamps.

     The main reason why I wrote it was because syslog does not consist of an
     ideal approach to count statistics, and that using an SQL server for this
     is overkill, especially with required SQL commands parsing and atomic-
     safe transaction locks. db4 could have been more efficient, but it is
     quite easy to rival with it according to size. The size of mmstatd and
     mmstat library is very small, and it's performance is decent. Moreover a
     database server would consider all keys as persistant storage, when a re-
     quirement for both persistant and volatile ones was met.

     The way it works

     Basically, it starts up two asynchroneous processes, the librarian and
     logger.

     The librarian is responsible for managing the database and affecting
     changes while asynchroneously reading available logs. It also permits ob-
     tention of statistics report connecting to a Unix domain stream socket.
     The librarian synchronizes the memory database to disk every once in a
     while, recording the current position in the logs, and deleting obsolete,
     already synchronized logs when required. This synchronization to disk is
     only performed at large time intervals, to minimize CPU and drive load,
     and maximise responsiveness.  The librarian also establishes a listening
     UNIX stream socket, to serve reports and rotation requests.

     The logger, in turn, listens to a Unix datagram socket, and writes the
     logs, syncing them to disk frequently enough, for both the librarian and
     logger.  This allows the logs to be used for recovery of persistant modi-
     fications that were performed since the last full database sync. More-
     over, it permits the clients to always be able to send more packets with-
     out being subject to the librarian processing, avoiding a bottleneck.

     Every time mmstatd is started, it first ensures to run with normal user
     privileges, then looks for recovery logs and performs necessary modifica-
     tions to the database, before forcing a sync of the new database to disk,
     deleting all recovery logs. It then launches the two asynchroneous pro-
     cesses which then become ready to serve their tasks.

     Using this design allows applications to use a simple syslog-like API to
     update statistics, in a very fast manner. For the various mm daemons, it
     serves as a who database, using volatile storage, and as various statis-
     tical tasks using persistant storage.

     The logging socket, used to send update requests, as well as the status
     socket, are independant and can have specific permissions, so that only
     applications who should access the service may. The user application in-
     terface library is quite simple to use by programs wanting to keep their
     statistics using mmstatd.  See the mmstat(3) man page for more informa-
     tion.

INSTALLATION
     mmstatd is installed by the make.sh scripts of both mmftpd and mmmail by
     Matthew Mondor. It's administration is made through /etc/mmstatd.conf
     (See mmstatd.conf(5) man page) and mmstat (See mmstat(8) man page).

     Here is an overview of standard permissions various files should have:

           Permissions Owner    Group   File

           -rwxr-x---  root     staff   /usr/local/sbin/mmstat
           -rwx------  root     wheel   /usr/local/sbin/mmstatd

           drwxr-x---  mmstatd  mmstat  /var/mmstatd

           s-w--w----  mmstatd  mmstat  /var/mmstatd/mmstatd_log.sock
           srw-rw----  mmstatd  staff   /var/mmstatd/mmstatd_stat.sock

     Basically, the administrator will need access to mmstat binary as well as
     to both /var/mmstatd/*.sock files. Applications using the mmstat(3) fa-
     cility require access to the /var/mmstatd/mmstatd_log.sock file only. On-
     ly uid zero should have access to /var/mmstatd directory and mmstatd dae-
     mon.

     mmstatd should normally be started before any other daemons using the
     mmstat(3) interface. Although this is not obligatory, it is highly recom-
     mended. As it will take the time to perform recovery before calling
     fork(2) other daemons will have a clean and ready daemon to serve their
     requests, so a startup script typically would use something like:

           /usr/local/sbin/mmstatd
           /usr/local/sbin/mmftpd
           /usr/local/sbin/mmsmtpd
           /usr/local/sbin/mmpop3d

FILES
     /etc/mmstatd.conf               This file consists of the configuration
                                     file for mmstatd and controls all it's
                                     configurable parameters.

     /var/mmstatd                    The mmstat environment directory, where
                                     recovery logs and database file are lo-
                                     cated. The default configuration also
                                     stores UNIX domain sockets there.

     /var/mmstatd/mmstatd_stat.sock  The UNIX stream socket on which listens
                                     mmstatd librarian process, used by the
                                     administrator via mmstat binary to query
                                     statistical reports and request key rota-
                                     tions.

     /var/mmstatd/mmstatd_log.sock   The UNIX datagram socket on which listens
                                     mmstatd logger process, used by all ap-
                                     plications using the mmstat(3) interface
                                     to update statistics.

     /var/mmstatd/mmstatd.db         The database file used to permanently
                                     store persistant storage statistical
                                     keys. When a disk synchronization occurs,
                                     a temporary file is used to save the
                                     database on the same filesystem, and
                                     rename(2) is used to move it over this
                                     file in an atomic manner.

     /var/mmstatd/????????.log       Log files internally used and automati-
                                     cally maintained by mmstatd for crash re-
                                     covery.

     /usr/local/sbin/mmstatd         The actual daemon binary documented by
                                     mmstatd(8)

     /usr/local/sbin/mmstat          The administration utility documented by
                                     mmstat(8)

AUTHOR
     The suite of mmstat daemon, related utilities and documentation were
     written by Matthew Mondor, and are Copyright (c) 2002-2003, Matthew Mon-
     dor, All rights reserved.  They were developped under NetBSD 1.5.3 for
     the mmftpd and mmmail suite of daemons from the same author.

SEE ALSO
     mmstat(3), mmstatd.conf(5), mmstat(8), rename(2), fork(2), unix(4).

BUGS
     The internal format of the log files and database file are not endian-in-
     dependant and will therefore only remain useable on architectures using
     the same endian format. Of course it would be possible to use mmstat(8)
     utility to perform exportation and importation to a new system for the
     time being.  This will eventually change and an endian-independant format
     will be used.

NetBSD 1.5.3                     11 Dec, 2002                                3