Linux Certif

Toute la documentation sur la certification Linux LPI

libwulf

NAME

libwulf - xmlsysd client library

SYNOPSIS

libwulf.a

DESCRIPTION

libwulf.a is the core common library required by wulfstat and wulflogger, two xmlsysd clients that poll and display various statistics from a cluster in a user-controllable loop. libwulf contains routines that open and parse a wulfhosts (cluster/lan descriptor) file, establish xmlsysd connections in a threaded subtask to all hosts in the wulfhosts file, and in parallel with this initialize and update selected statistics. libwulf functions form an API adequate to support many kinds of toplevel log and gui applications reasonably efficiently.

The best way to develop an application using libwulf is to examine one of the existing applications such as wulflogger. The steps are roughly as follows:

  * Initialize libxml

  * Allocate various linked lists using the provided linked list routines

  * Read and parse the wulfhosts file

  * Set the dctl (display control) state for all hosts.  This struct MUST correspond to the state of the xmlsysd on the hosts.

  * Connect to all hosts, generally in a threaded loop that runs in parallel with any display process (so that if a host goes down the display task does not block).

  * Initialize all host-derived values from an initial xmlsysd return

  * Enter a polling work loop that sends all hosts the "send" commmand, updates all host derived values and then sleeps. This loop can contain branches that alter dctl state, alter the display, or do pretty much whatever you want with the data retrieved.

  * Display or otherwise utilize the per-host data.

  * Exit (cleanly or otherwise) on request.

DCTL FLAGS

The following is the dctl struct currently used by libwulf. The contents are all flags that can take on values of 0 (no or false) or not-zero (yes or true). There is a fairly straightforward correspondance between dctl state flags and throttleable xmlsysd tags and their (possibly sub-tagged) contents.

 typedef struct {

   int compress;        /* Do we compress xml output? */

   int whitespace;      /* Do we squeeze out whitespace? */

   /*
    * All the following toggle various components of the return.  Some of
    * these are only needed "once" in a typical monitoring session anyway
    * and can be pulled from the init return (which always sends
    * "everything").  Future developers should note the 1:1 correspondance
    * between many of these flags and "init_XXXX.c" and "update_XXXX.c"
    * sources and calls.
    */

   /* system call stuff */
   int identity;        /* Do we update system identity? */

   int time;            /* Do we update system time? */

   int users;           /* Do we update system pids? */

   /* proc-derived stuff */
   int cpuinfo;         /* Do we update proc cpuinfo? */

   int loadavg;         /* Do we update proc loadavg? */

   int meminfo;         /* Do we update proc meminfo? */

   int net;             /* Do we update proc net? */

   int stat;            /* Do we update proc stat? */

   int sysvipc;         /* Do we update proc shared memory stuff? */

   int uptime;          /* Do we update proc uptime? */

   int version;         /* Do we update proc (kernel) version? */

   /* Processes (in /proc/XXXXX where XXXXX is a pid) */
   int pids;            /* Do we update pids at all? */

   int running;         /* Running PIDs or all? */

   int root;            /* Including those owned by root? */

   List *userlist;      /* A linked list of usernames to watch */

   List *tasklist;      /* A linked list of tasknames to watch */

 } Dctl;

SEE ALSO:

wulfstat(1), wulflogger(1)

PUBLICATION RULES

libwulf.a can be modified and used at will by any user, provided that:

  a) The original copyright notices are maintained and that the source, including all modifications, is made publically available at the time of any derived publication. This is open source software according to the precepts and spirit of the Gnu Public License. See the accompanying file COPYING, which also must accompany any redistribution.

  b) The author of the code (Robert G. Brown) is appropriately acknowledged and referenced in any derived use or publication.

  c) Full responsibility for the accuracy, suitability, and effectiveness of the program rests with the users and/or modifiers. As is clearly stated in the accompanying copyright.h:

THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

ACKNOWLEDGEMENTS

None to speak of now, but a good place to comply with b) above later, if you hack this code. Well, I should probably acknowledge the essential help of Icon (Konstantin Raibetsev) and Seth Vidal, the entire beowulf list, and various books on xml, network programming (e.g. Stevens) and a cast of thousands. So let's assume that I just did;-)

GPL 2b; see the file COPYING that accompanies the source of this program. This is the "standard Gnu General Public License version 2 or any later version", with the one minor (humorous) "Beverage" modification listed below. Note that this modification is probably not legally defensible and can be followed really pretty much according to the honor rule.

As to my personal preferences in beverages, red wine is great, beer is delightful, and Coca Cola or coffee or tea or even milk acceptable to those who for religious or personal reasons wish to avoid stressing my liver.

The Beverage Modification to the GPL:

Any satisfied user of this software shall, upon meeting the primary author(s) of this software for the first time under the appropriate circumstances, offer to buy him or her or them a beverage. This beverage may or may not be alcoholic, depending on the personal ethical and moral views of the offerer. The beverage cost need not exceed one U.S. dollar (although it certainly may at the whim of the offerer:-) and may be accepted or declined with no further obligation on the part of the offerer. It is not necessary to repeat the offer after the first meeting, but it can't hurt...