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    1: #!/usr/bin/perl
    2: #
    3: # The LearningOnline Network with CAPA
    4: # Connect to MAXIMA CAS
    5: #
    6: # $Id: lonmaxima,v 1.15 2006/03/08 15:58:03 www Exp $
    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: #
   32: 
   33:  
   34: use IPC::Open3;
   35: use IO::Select;
   36: use IO::Socket;
   37: use IO::File;
   38: use Symbol;
   39: use POSIX;
   40: use lib '/home/httpd/lib/perl/';
   41: use LONCAPA::Configuration;
   42:  
   43: use strict;
   44: 
   45: # global variables
   46: my $STARTPORT              = 5664;     # port for first child's server
   47: my $PREFORK                = 5;        # number of children to maintain
   48: my $MAX_CLIENTS_PER_CHILD  = 5;        # number of clients each child should process
   49: my %children               = ();       # keys are current child process IDs
   50: my %usedmaximaports        = ();       # keys are the used maximaports
   51: my $children               = 0;        # current number of children
   52: my $status;                            # string for current status
   53: my $pidfile;                           # file containg parent process pid
   54: my $port;                              # path to UNIX socket file
   55: my %perlvar;                           # configuration file info
   56: my $lastlog;                           # last string that was logged
   57: use vars qw($PREFORK $MAX_CLIENTS_PER_CHILD %children $children %usedmaximaports $status
   58: 	    $pidfile $port %perlvar $lastlog);
   59:  
   60: # ------------------------------------------------------------ Service routines 
   61: sub REAPER {                        # takes care of dead children 
   62:                                     # and MAXIMA processes
   63:     $SIG{CHLD} = \&REAPER;
   64:     my $pid = wait;
   65:     $children--;
   66:     &logthis("Child $pid for port or process $children{$pid} died");
   67:     delete($usedmaximaports{$children{$pid}});
   68:     delete($children{$pid});
   69: }
   70:  
   71: sub HUNTSMAN {                      # signal handler for SIGINT
   72:     local($SIG{CHLD}) = 'IGNORE';   # we're going to kill our children
   73:     kill('INT' => keys(%children));
   74:     unlink($pidfile);
   75:     unlink($port);
   76:     &logthis('---- Shutdown ----');
   77:     exit;                           # clean up with dignity
   78: }
   79: 
   80: 
   81:  
   82: # --------------------------------------------------------------------- Logging
   83:  
   84: sub logthis {
   85:     my ($message)=@_;
   86:     my $execdir=$perlvar{'lonDaemons'};
   87:     my $fh=IO::File->new(">>$execdir/logs/lonmaxima.log");
   88:     my $now=time;
   89:     my $local=localtime($now);
   90:     $lastlog=$local.': '.$message;
   91:     print $fh "$local ($$): $message\n";
   92: }
   93:  
   94: # -------------------------------------------------------------- Status setting
   95:  
   96: sub status {
   97:     my ($what)=@_;
   98:     my $now=time;
   99:     my $local=localtime($now);
  100:     $status=$local.': '.$what;
  101:     $0='lonmaxima: '.$what.' '.$local;
  102: }
  103:  
  104: # -------------------------------------------------------- Escape Special Chars
  105:  
  106: sub escape {
  107:     my ($str)=@_;
  108:     $str =~ s/(\W)/"%".unpack('H2',$1)/eg;
  109:     return $str;
  110: }
  111:  
  112: # ----------------------------------------------------- Un-Escape Special Chars
  113:  
  114: sub unescape {
  115:     my ($str)=@_;
  116:     $str =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg;
  117:     return $str;
  118: }
  119:  
  120: # ------------------------ grabs exception and records it to log before exiting
  121: sub catchexception {
  122:     my ($signal)=@_;
  123:     $SIG{QUIT}='DEFAULT';
  124:     $SIG{__DIE__}='DEFAULT';
  125:     chomp($signal);
  126:     &logthis("<font color=\"red\">CRITICAL: "
  127: 	     ."ABNORMAL EXIT. Child $$ died through "
  128: 	     ."\"$signal\"</font>");
  129:     die("Signal abend");
  130: }
  131: 
  132: # ---------------------------------------------------------------- Main program
  133: # -------------------------------- Set signal handlers to record abnormal exits
  134:  
  135:  
  136: $SIG{'QUIT'}=\&catchexception;
  137: $SIG{__DIE__}=\&catchexception;
  138:  
  139: # ---------------------------------- Read loncapa_apache.conf and loncapa.conf
  140: &status("Read loncapa.conf and loncapa_apache.conf");
  141: %perlvar=%{&LONCAPA::Configuration::read_conf('loncapa.conf')};
  142:  
  143: # ----------------------------- Make sure this process is running from user=www
  144: my $wwwid=getpwnam('www');
  145: if ($wwwid!=$<) {
  146:     my $emailto="$perlvar{'lonAdmEMail'},$perlvar{'lonSysEMail'}";
  147:     my $subj="LON: User ID mismatch";
  148:     system("echo 'User ID mismatch.  lonmaxima must be run as user www.' |\
  149:  mailto $emailto -s '$subj' > /dev/null");
  150:     exit 1;
  151: }
  152:  
  153: # --------------------------------------------- Check if other instance running
  154:  
  155: $pidfile="$perlvar{'lonDaemons'}/logs/lonmaxima.pid";
  156:  
  157: if (-e $pidfile) {
  158:     my $lfh=IO::File->new("$pidfile");
  159:     my $pide=<$lfh>;
  160:     chomp($pide);
  161:     if (kill(0 => $pide)) { die "already running"; }
  162: }
  163: 
  164: # ------------------------------------------------------- Listen to UNIX socket
  165: &status("Opening socket");
  166:  
  167: $port = "$perlvar{'lonSockDir'}/maximasock";
  168:  
  169: unlink($port);
  170:  
  171: 
  172: my $server = IO::Socket::UNIX->new(Local  => $port,
  173: 				   Type   => SOCK_STREAM,
  174: 				   Listen => 10 );
  175: if (!$server) {
  176:     my $st=120+int(rand(240));
  177: 
  178:     &logthis("<font color=blue>WARNING: ".
  179: 	     "Can't make server socket ($st secs):  .. exiting</font>");
  180: 
  181:     sleep($st);
  182:     exit;
  183: }
  184:     
  185:  
  186: # ---------------------------------------------------- Fork once and dissociate
  187:  
  188: my $fpid=fork;
  189: exit if $fpid;
  190: die("Couldn't fork: $!") unless defined($fpid);
  191:  
  192: POSIX::setsid() or die "Can't start new session: $!";
  193:  
  194: # ------------------------------------------------------- Write our PID on disk
  195:  
  196: my $execdir=$perlvar{'lonDaemons'};
  197: open(PIDSAVE,">$execdir/logs/lonmaxima.pid");
  198: print PIDSAVE "$$\n";
  199: close(PIDSAVE);
  200: &logthis("<font color='red'>CRITICAL: ---------- Starting ----------</font>");
  201: &status('Starting');
  202:      
  203: 
  204: # Install signal handlers.
  205: $SIG{CHLD} = \&REAPER;
  206: $SIG{INT}  = $SIG{TERM} = \&HUNTSMAN;
  207: 
  208: my $maximaport=$STARTPORT; 
  209: # Fork off our children.
  210: for (1 .. $PREFORK) {
  211:     &make_new_child($server,$maximaport);
  212:     $maximaport++;
  213: }
  214:  
  215: # And maintain the population.
  216: while (1) {
  217:     &status('Parent process, sleeping');
  218:     sleep;                          # wait for a signal (i.e., child's death)
  219:     for (my $i = $children; $i < $PREFORK; $i++) {
  220:         &status('Parent process, starting child');
  221:         my $newport;
  222:         &logthis("Current pool: ".join(', ',keys %usedmaximaports));
  223:         foreach my $testport ($STARTPORT .. $STARTPORT+$PREFORK-1) {
  224:             if (!$usedmaximaports{$testport}) { $newport=$testport; }
  225:         }
  226:         if ($newport) {
  227:            &make_new_child($server,$newport);           # top up the child pool
  228:         }
  229:     }
  230: }
  231:                                                                                 
  232: sub make_new_child {
  233:     my ($server,$maximaport) = @_;
  234: 
  235:     # block signal for fork
  236:     my $sigset = POSIX::SigSet->new(SIGINT);
  237:     sigprocmask(SIG_BLOCK, $sigset)
  238:         or die("Can't block SIGINT for fork: $!\n");
  239:      
  240:     die("fork: $!") unless defined(my $pid = fork);
  241:      
  242:     if ($pid) {
  243:         # Parent records the child's birth and returns.
  244:         sigprocmask(SIG_UNBLOCK, $sigset)
  245:             or die("Can't unblock SIGINT for fork: $!\n");
  246:         $children{$pid} = $maximaport;
  247:         $children++;
  248:         $usedmaximaports{$maximaport}=1;
  249:         return;
  250:     } else {
  251:         &logthis("Starting child on port $maximaport");
  252:         # Child can *not* return from this subroutine.
  253:         $SIG{INT} = 'DEFAULT';      # make SIGINT kill us as it did before
  254:      
  255:         # unblock signals
  256:         sigprocmask(SIG_UNBLOCK, $sigset)
  257:             or die("Can't unblock SIGINT for fork: $!\n");
  258:         
  259:         # open the MAXIMA port
  260:         my $maximaserver = IO::Socket::INET->new(LocalPort => $maximaport,
  261:                                               Type      => SOCK_STREAM,
  262:                                               Proto     => 'tcp',
  263:                                               Reuse     => 1,
  264:                                               Listen    => 10 )
  265:                         or die "making socket: $@\n";
  266:         my $maximaselect=IO::Select->new($maximaserver);
  267:         sleep(1);
  268: 
  269:         # open MAXIMA to talk to that port
  270:         my ($cmd_in, $cmd_out, $cmd_err);
  271:         my $maximapid = open3($cmd_in, $cmd_out, $cmd_err, "maxima -s $maximaport");
  272:         $children{$maximapid} = "Maxima $maximapid port $maximaport";
  273:         my $prompt=<$cmd_out>;
  274:         &logthis("Maxima $maximapid: $prompt");
  275: 
  276:         # hopefully, MAXIMA calls us back
  277:         &status("Waiting $maximapid on $maximaport");
  278:         my $maximaclient=$maximaserver->accept();
  279:         $maximaclient->blocking(0);
  280:         $maximaselect->add($maximaclient);
  281:         &status("$maximapid on $maximaport connected.");
  282:         &logthis("Maxima $maximapid on port $maximaport connected.");
  283:         sleep(2);
  284: 
  285:         &logthis('Initial reply: '.&maximareply($maximaselect));
  286:         # handle connections until we've reached $MAX_CLIENTS_PER_CHILD
  287:         for (my $i=0; $i < $MAX_CLIENTS_PER_CHILD; $i++) {
  288:             &status('Accepting connections for '.$maximapid.' on '.$maximaport);
  289:             my $client = $server->accept()     or last;
  290:             while (my $cmd=<$client>) {
  291:                 &status('Processing command by '.$maximapid.' on '.$maximaport);
  292:                 &maximawrite($maximaselect,&unescape($cmd).";\n");
  293:                 print $client &escape(&maximareply($maximaselect))."\n";
  294:             }
  295:         }
  296: 
  297:         # tidy up gracefully and finish
  298: 
  299:         if (ref($cmd_out)) { close($cmd_out); }
  300:         if (ref($cmd_err)) { close($cmd_err); }
  301:         if (ref($cmd_in)) { close($cmd_in); }
  302: 
  303:         # this exit is VERY important, otherwise the child will become
  304:         # a producer of more and more children, forking yourself into
  305:         # process death.
  306:         exit;
  307:     }
  308: }
  309: 
  310: sub maximareply {
  311:    my ($maximaselect)=@_;
  312:    my $output='';
  313:    
  314:    foreach my $ready ($maximaselect->can_read(1)) {
  315:        my $data = '';
  316:        my $rv   = $ready->recv($data, POSIX::BUFSIZ, 0);
  317:        $output.=$data;
  318:    }
  319:    return $output;
  320: }
  321: 
  322: sub maximawrite {
  323:    my ($maximaselect,$cmd)=@_;
  324:    my $ready=($maximaselect->can_write(1));
  325:    if (ref($ready)) {
  326:       print $ready $cmd;
  327:    } else {
  328:       &logthis("Cannot write: ".&maximareply($maximaselect));
  329:    }
  330: }
  331: 
  332: