Annotation of loncom/lonmaxima, revision 1.2

1.1       www         1: #!/usr/bin/perl
                      2: #
                      3: # The LearningOnline Network with CAPA
                      4: # Connect to MAXIMA CAS
                      5: #
1.2     ! www         6: # $Id: lonmaxima,v 1.1 2006/03/03 16:07:34 www Exp $
1.1       www         7: #
                      8: # Copyright Michigan State University Board of Trustees
                      9: #
                     10: # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
                     11: #
                     12: # LON-CAPA is free software; you can redistribute it and/or modify
                     13: # it under the terms of the GNU General Public License as published by
                     14: # the Free Software Foundation; either version 2 of the License, or
                     15: # (at your option) any later version.
                     16: #
                     17: # LON-CAPA is distributed in the hope that it will be useful,
                     18: # but WITHOUT ANY WARRANTY; without even the implied warranty of
                     19: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
                     20: # GNU General Public License for more details.
                     21: #
                     22: # You should have received a copy of the GNU General Public License
                     23: # along with LON-CAPA; if not, write to the Free Software
                     24: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
                     25: #
                     26: # /home/httpd/html/adm/gpl.txt
                     27: #
                     28: 
                     29: # 
                     30: # http://www.lon-capa.org/
                     31: #
1.2     ! www        32: 
        !            33: # global variables
        !            34: $PREFORK                = 5;        # number of children to maintain
        !            35: $MAX_CLIENTS_PER_CHILD  = 5;        # number of clients each child should process
        !            36: %children               = ();       # keys are current child process IDs
        !            37: $children               = 0;        # current number of children
1.1       www        38:  
                     39: use IPC::Open3;
                     40: use IO::Select;
1.2     ! www        41: use IO::Socket;
        !            42: use IO::File;
        !            43: use Symbol;
        !            44: use POSIX;
        !            45: use lib '/home/httpd/lib/perl/';
        !            46: use LONCAPA::Configuration;
        !            47:  
1.1       www        48: # Scary: cannot use strict!!!
                     49: ##### use strict;
1.2     ! www        50:  
1.1       www        51: sub maximareply {
                     52:     my $cmd=shift;
                     53:     my $reply='';
                     54:     my $error='';
                     55:     my $exitstatus='';
                     56: 
                     57:     unless ($cmd=~/\;\n$/) { $cmd.=";\n"; }
                     58:     my $pid = open3($cmd_in, $cmd_out, $cmd_err, 'maxima');
1.2     ! www        59:     $children{$pid} = 1;
1.1       www        60:     
                     61:     print $cmd_in $cmd;
                     62:     close $cmd_in;
                     63: 
1.2     ! www        64:     &status("Command sent");
        !            65: 
        !            66:     my $selector = IO::Select->new();
1.1       www        67:     $selector->add($cmd_err, $cmd_out);
                     68:     
                     69:     while (my @ready = $selector->can_read) {
                     70: 	foreach my $fh (@ready) {
                     71: 	    if (fileno($fh) == fileno($cmd_err)) {
                     72: 		$error.=<$cmd_err>;
                     73: 	    } else {
                     74: 		my $line = scalar <$cmd_out>;
                     75:                 if ($line=~/^(\(\%o|\s)/) {
                     76:                    $line=~s/^\(.*\)/     /; 
                     77:                    $reply.=$line; 
                     78: 	       }
                     79: 	    }
                     80: 	    $selector->remove($fh) if eof($fh);
                     81: 	}
                     82:     }
                     83:     close $cmd_out;
                     84:     close $cmd_err;
1.2     ! www        85:     &status("Command processed");
1.1       www        86:     return ($reply,$error,$exitstatus);
                     87: }
1.2     ! www        88:  
        !            89: # ------------------------------------------------------------ Service routines 
        !            90: sub REAPER {                        # takes care of dead children 
        !            91:                                     # and MAXIMA processes
        !            92:     $SIG{CHLD} = \&REAPER;
        !            93:     my $pid = wait;
        !            94:     $children --;
        !            95:     delete $children{$pid};
        !            96: }
        !            97:  
        !            98: sub HUNTSMAN {                      # signal handler for SIGINT
        !            99:     local($SIG{CHLD}) = 'IGNORE';   # we're going to kill our children
        !           100:     kill 'INT' => keys %children;
        !           101:     unlink($pidfile);
        !           102:     unlink($port);
        !           103:     &logthis('---- Shutdown ----');
        !           104:     exit;                           # clean up with dignity
        !           105: }
        !           106: 
        !           107: 
        !           108:  
        !           109: # --------------------------------------------------------------------- Logging
        !           110:  
        !           111: sub logthis {
        !           112:     my $message=shift;
        !           113:     my $execdir=$perlvar{'lonDaemons'};
        !           114:     my $fh=IO::File->new(">>$execdir/logs/lonmaxima.log");
        !           115:     my $now=time;
        !           116:     my $local=localtime($now);
        !           117:     $lastlog=$local.': '.$message;
        !           118:     print $fh "$local ($$): $message\n";
        !           119: }
        !           120:  
        !           121: # -------------------------------------------------------------- Status setting
        !           122:  
        !           123: sub status {
        !           124:     my $what=shift;
        !           125:     my $now=time;
        !           126:     my $local=localtime($now);
        !           127:     $status=$local.': '.$what;
        !           128:     $0='lonmaxima: '.$what.' '.$local;
        !           129: }
        !           130:  
        !           131: # -------------------------------------------------------- Escape Special Chars
        !           132:  
        !           133: sub escape {
        !           134:     my $str=shift;
        !           135:     $str =~ s/(\W)/"%".unpack('H2',$1)/eg;
        !           136:     return $str;
        !           137: }
        !           138:  
        !           139: # ----------------------------------------------------- Un-Escape Special Chars
        !           140:  
        !           141: sub unescape {
        !           142:     my $str=shift;
        !           143:     $str =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg;
        !           144:     return $str;
        !           145: }
        !           146:  
        !           147: # ------------------------ grabs exception and records it to log before exiting
        !           148: sub catchexception {
        !           149:     my ($signal)=@_;
        !           150:     $SIG{QUIT}='DEFAULT';
        !           151:     $SIG{__DIE__}='DEFAULT';
        !           152:     chomp($signal);
        !           153:     &logthis("<font color=red>CRITICAL: "
        !           154:      ."ABNORMAL EXIT. Child $$ died through "
        !           155:      ."\"$signal\"</font>");
        !           156:     die("Signal abend");
        !           157: }
        !           158:  
        !           159: 
        !           160: 
        !           161: # ---------------------------------------------------------------- Main program
        !           162: # -------------------------------- Set signal handlers to record abnormal exits
        !           163:  
        !           164:  
        !           165: $SIG{'QUIT'}=\&catchexception;
        !           166: $SIG{__DIE__}=\&catchexception;
        !           167:  
        !           168: # ---------------------------------- Read loncapa_apache.conf and loncapa.conf
        !           169: &status("Read loncapa.conf and loncapa_apache.conf");
        !           170: my $perlvarref=LONCAPA::Configuration::read_conf('loncapa.conf');
        !           171: %perlvar=%{$perlvarref};
        !           172: undef $perlvarref;
        !           173:  
        !           174: # ----------------------------- Make sure this process is running from user=www
        !           175: my $wwwid=getpwnam('www');
        !           176: if ($wwwid!=$<) {
        !           177:    my $emailto="$perlvar{'lonAdmEMail'},$perlvar{'lonSysEMail'}";
        !           178:    my $subj="LON: $currenthostid User ID mismatch";
        !           179:    system("echo 'User ID mismatch.  lonmaxima must be run as user www.' |\
        !           180:  mailto $emailto -s '$subj' > /dev/null");
        !           181:    exit 1;
        !           182: }
        !           183:  
        !           184: # --------------------------------------------- Check if other instance running
        !           185:  
        !           186: $pidfile="$perlvar{'lonDaemons'}/logs/lonmaxima.pid";
        !           187:  
        !           188: if (-e $pidfile) {
        !           189:    my $lfh=IO::File->new("$pidfile");
        !           190:    my $pide=<$lfh>;
        !           191:    chomp($pide);
        !           192:    if (kill 0 => $pide) { die "already running"; }
        !           193: }
        !           194: # ------------------------------------------------------- Listen to UNIX socket
        !           195: &status("Opening socket");
        !           196:  
        !           197: $port = "$perlvar{'lonSockDir'}/maximasock";
        !           198:  
        !           199: unlink($port);
        !           200:  
        !           201: 
        !           202: unless (
        !           203:   $server = IO::Socket::UNIX->new(Local  => $port,
        !           204:                                   Type   => SOCK_STREAM,
        !           205:                                   Listen => 10 )
        !           206:    ) {
        !           207:        my $st=120+int(rand(240));
        !           208:        &logthis(
        !           209:          "<font color=blue>WARNING: ".
        !           210:          "Can't make server socket ($st secs):  .. exiting</font>");
        !           211:        sleep($st);
        !           212:        exit;
        !           213:      };
        !           214:     
        !           215:  
        !           216: # ---------------------------------------------------- Fork once and dissociate
        !           217:  
        !           218: my $fpid=fork;
        !           219: exit if $fpid;
        !           220: die "Couldn't fork: $!" unless defined ($fpid);
        !           221:  
        !           222: POSIX::setsid() or die "Can't start new session: $!";
        !           223:  
        !           224: # ------------------------------------------------------- Write our PID on disk
        !           225:  
        !           226: my $execdir=$perlvar{'lonDaemons'};
        !           227: open (PIDSAVE,">$execdir/logs/lonmaxima.pid");
        !           228: print PIDSAVE "$$\n";
        !           229: close(PIDSAVE);
        !           230: &logthis("<font color='red'>CRITICAL: ---------- Starting ----------</font>");
        !           231: &status('Starting');
        !           232:  
        !           233:  
        !           234: 
        !           235: 
        !           236:      
        !           237: # Fork off our children.
        !           238: for (1 .. $PREFORK) {
        !           239:     make_new_child( );
        !           240: }
        !           241:  
        !           242: # Install signal handlers.
        !           243: $SIG{CHLD} = \&REAPER;
        !           244: $SIG{INT}  = $SIG{TERM} = \&HUNTSMAN;
        !           245:  
        !           246: # And maintain the population.
        !           247: while (1) {
        !           248:     &status('Parent process, sleeping');
        !           249:     sleep;                          # wait for a signal (i.e., child's death)
        !           250:     for ($i = $children; $i < $PREFORK; $i++) {
        !           251:         &status('Parent process, starting child');
        !           252:         make_new_child( );           # top up the child pool
        !           253:     }
        !           254: }
        !           255:                                                                                 
        !           256: sub make_new_child {
        !           257:     my $pid;
        !           258:     my $sigset;
        !           259:      
        !           260:     # block signal for fork
        !           261:     $sigset = POSIX::SigSet->new(SIGINT);
        !           262:     sigprocmask(SIG_BLOCK, $sigset)
        !           263:         or die "Can't block SIGINT for fork: $!\n";
        !           264:      
        !           265:     die "fork: $!" unless defined ($pid = fork);
        !           266:      
        !           267:     if ($pid) {
        !           268:         # Parent records the child's birth and returns.
        !           269:         sigprocmask(SIG_UNBLOCK, $sigset)
        !           270:             or die "Can't unblock SIGINT for fork: $!\n";
        !           271:         $children{$pid} = 1;
        !           272:         $children++;
        !           273:         return;
        !           274:     } else {
        !           275:         # Child can *not* return from this subroutine.
        !           276:         $SIG{INT} = 'DEFAULT';      # make SIGINT kill us as it did before
        !           277:      
        !           278:         # unblock signals
        !           279:         sigprocmask(SIG_UNBLOCK, $sigset)
        !           280:             or die "Can't unblock SIGINT for fork: $!\n";
        !           281:          
        !           282:         # handle connections until we've reached $MAX_CLIENTS_PER_CHILD
        !           283:         for ($i=0; $i < $MAX_CLIENTS_PER_CHILD; $i++) {
        !           284: 	    &status('Accepting connections');     
        !           285:             $client = $server->accept( )     or last;
        !           286:             while ($cmd=<$client>) {
        !           287: 		&status('Processing command');
        !           288: 		print $client &escape((&maximareply(&unescape($cmd)))[0])."\n";
        !           289: 	    }
        !           290:         }
        !           291:      
        !           292:         # tidy up gracefully and finish
1.1       www       293: 
1.2     ! www       294:         # this exit is VERY important, otherwise the child will become
        !           295:         # a producer of more and more children, forking yourself into
        !           296:         # process death.
        !           297:         exit;
        !           298:     }
        !           299: }

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