grmd-0.3 -- General Resource Management Daemon for UNIX-like systems

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Introduction

grmd is a daemon program on UNIX-like systems which provide general management feature for every resources.

usually in exclusive lock control of files, programer use busy-wait method with mkdir(),symlink() etc, or use flock(),lockf(),fcntl() etc. and in exclusive lock control of some resources except for files, programer use semaphore. these quality level of exclusive lock control is not constant by programer's skill level. and it is hard to get unified exclusive lock control in whole system, bacause of non-unified program coding in every programs. and even if excellent programer design exclusive lock control, there will be unavoidable difficulty like a deadlock problem.

grmd control exclusive lock with client-server method, you can control exclusive lock of every resources with unified interface. grmd have following features.

grmd have 2-level exclusive lock(SHARED_LOCK, EXCUSIVE_LOCK) and help multiplex.
if resource is locked already by another process, process go into sleep mode(not busy-wait). and when resource is released by another process, process wakeup automatically.
grmd notice deadlock status to client instantly, when deadlock happen.

download

grmd-0.3.tar.gz 2007.02.15 (LATEST)
- change for right way to be daemon process.
- change for better signal handling.
- change way to option handling.
- change default host to NADDR_ANY.
- change max length of pid, resid, key from 64 to 256.
- fix seg fault when access denied by libwrap.
grmd-0.2.tar.gz 2007.02.01
- change install location of grm.pl to /usr/local/grm/
- fix seg fault when adminkeystr is not specified with srp, spr.
  define PATH in rc.grmd.
- add grm_getpr_first(), grm_getpr_next(), grm_getpr_item().
  add getpr admin_keystring command(order by pid, resid)
- add -lnsl to LIBS in Makefile.
- add grm_getrp_first(), grm_getrp_next(), grm_getrp_item().
  add getrp admin_keystring command(order by resid, pid)
- add sample perl script(grmd_sweep.pl) to unlock forced zombi lock.
grmd-0.1.tar.gz 2004.06.18
- first release.

Install

$ tar xvzf grmd-0.3.tar.gz
$ cd grmd-0.3
$ vi Makefile
$ make
$ su
# make install
# vi /usr/local/grmd/keystring  # key string for administrator(MAX 256chars)
# vi /etc/hosts.allow
# vi /etc/hosts.deny

(*) SYSVMSG option is needed for kernel configuration of BSD-like system.

Execute

# /usr/local/grmd/rc.grmd

Run script

$ /usr/local/grmd/rc.grmd -h
usage : rc.grmd [-d|--dir home_directory] [-H|--host hostname] [-p|--port port] 
                [-q|--queue queue_count] [-k|--key keystring_file] [-l|--log logfile] [-f|--foreground]

  -d|--dir home_directory ... home directory. [/usr/local/grmd]
  -H|--host hostname      ... hostname which daemon run in. [localhost]
  -p|--port port          ... socket port which client talk to. [20100]
  -q|--queue queue_count  ... queue count of socket backlog. [128]
  -k|--key keystring_file ... file (in home_directory) which administrator keystring is written in. [keystring]
  -l|--log logfile        ... file (in home_directory) which daemon record messages to. [logfile]
  -f|--foreground         ... run in foreground [none]

Exclusive lock

grmd have `SHARE_LOCK' and `EXCLUSIVE_LOCK' in lock mode. (1) is first process, (2) is second process.

Table.1
	SHARE_LOCK(1)	EXCLUSIVE_LOCK(1)
SHARE_LOCK(2)	Get lock	Wait for release
EXCLUSIVE_LOCK(2)	Wait for release	Wait for release

Deadlock detection

when loop status appear in resource allocation graph(fig.1 - fig.4), grmd notice deadlock status to client. usually process which get deadlock status must release all resource locked myself and rollback. after that process can lock resources again.

      GET LOCK
     +---------------->(Process 1)
     |
     |
     |
[Resource 1]                                  [Resource 2]



                       (Process 2)

                          (fig.1)

      GET LOCK
     +---------------->(Process 1)
     |
     |
     |
[Resource 1]                                  [Resource 2]
                                                   |
                                                   |
                                                   |
                       (Process 2)<----------------+
                                           GET LOCK
                          (fig.2)

      GET LOCK                            WAIT LOCK      
     +---------------->(Process 1).................+
     |                                             :
     |                                             :
     |                                             v
[Resource 1]                                  [Resource 2]
                                                   |
                                                   |
                                                   |
                       (Process 2)<----------------+
                                           GET LOCK
                          (fig.3)

      GET LOCK                            WAIT LOCK
     +---------------->(Process 1).................+
     |                                             :
     |                                             :
     |                                             v
[Resource 1]                                  [Resource 2]
     X                                             |
     :                                             |
     :                                             |
     +.................(Process 2)<----------------+
      DEADLOCK!!                           GET LOCK

                          (fig.4)

Interface

grmd accept command from socket interface. client send command string into socket port(default 20100) which is opend by grmd, and client get status from same port. grmd can accept following command string. token separater is TAB(0x09). command string must be ended by NL('\n').

lock pid resid lockmode keystring

  function  : lock resource. if resource is already locked by another 
              process, process will wait till resource is released.
  pid       : string which show process id(max 256chars).
  resid     : string which show resource id(max 256chars).
  lockmode  : string which show exclusive lock mode(case insensitive).
              share_lock, sl, s
              exclusive_lock, el, x
  keystring : keystring which should be specified at unlock(max 256chars).

return : OK       : exclusive lock success
         DEADLOCK : exclusive lock failure(DEADLOCK)
         NG       : exclusive lock failure

unlock pid resid keystring

  function  : release resource and wakeup next process waiting.
  pid       : string which show process id(max 256chars).
  resid     : string which show resource id(max 256chars).
  keystring : keystring which is specified at lock(max 256chars).

return : OK       : release success
         NG       : release failure

spr keystring

  function  : output resource status into logfile(pid-resid).
  keystring : keystring for administrator(max 256chars).

return : OK       : success
         NG       : failure

srp keystring

  function  : output resource status into logfile(resid-pid).
  keystring : keystring for administrator(max 256chars).

return : OK       : success
         NG       : failure

getpr keystring

  function  : get resource status(pid-resid)ĄŁ
  keystring : keystring for administrator(max 256chars).

return : OK pid resid status keystr : success
         NG                         : failure

getrp keystring

  function  : get resource status(resid-pid)ĄŁ
  keystring : keystring for administrator(max 256chars).

return : OK resid pid status keystr : success
         NG                         : failure

Perl interface

grm.pl is perl interface routin. see sample*.pl to get howto use.

function : lock resource
argment  : host, port, pid, resid, lockmode, keystring
return   : status
ex.      : $status = grm_lock("localhost", "20100", "process1", "resource1", "SHARE_LOCK", "Gehime");

lockmode : SHARE_LOCK, SL, S
           EXCLUSIVE_LOCK, EL, X

function : release resource
argment  : host, port, pid, resid, keystring
return   : status
ex.      : $status = grm_unlock("localhost", "20100", "process1", "resource1", "Gehime");

function : output resource status into logfile(pid-resid)
argment  : host, port, keystring
return   : status
ex.      : $status = grm_spr("localhost", "20100", "Gehime");

function : output resource status into logfile(resid-pid)
argment  : host, port, keystring
return   : status
ex.      : $status = grm_srp("localhost", "20100", "Gehime");

function : get resource status(pid-resid)
argment  : host, port, keystring
return   : status pid resid status keystr
ex.      : $responce = grm_getpr("localhost", "20100", "Gehime");
           @stat_pid_resid_status_keystr = split(/\n/, $responce);
           foreach $i (@stat_pid_resid_status_keystr){
               ($stat, $pid, $resid, $status, $keystr) = split(/\t/, $i);
           }

function : get resource status(resid-pid)
argment  : host, port, keystring
return   : status resid pid status keystr
ex.      : $responce = grm_getrp("localhost", "20100", "Gehime");
           @stat_resid_pid_status_keystr = split(/\n/, $responce);
           foreach $i (@stat_resid_pid_status_keystr){
               ($stat, $resid, $pid, $status, $keystr) = split(/\t/, $i);
           }

Howto run sample script(perl)

# sample1.pl lock resource `r1.txt' and `r2.txt', add 1 to data 
# in resource 100 times as process `p1'.
#
# sample2.pl lock resource `r2.txt' and `r1.txt', add 1 to data 
# in resource 100 times as process `p2'.
#
# sample3.pl lock resource `r1.txt' and `r2.txt', add 1 to data 
# in resource 100 times as process `p2'.

#
# pattern which deadlock happen
# 
$ ./sample1 localhost 20100 & ./sample2 localhost 20100

#
# pattern which deadlock don't happen
# 
$ ./sample1 localhost 20100 & ./sample3 localhost 20100

force to unlock script(perl sample)

To use this script, you have to specify OS process id(getpid()) to pid for `lock' command.

$ ./grmd_sweep.pl localhost 20100

BUGS

when process which get exclusive lock exit without release resource, resource will not be released automatically.

Masahiko Ito <m-ito@myh.no-ip.org>