--- loncom/lonmaxima 2006/03/03 16:07:34 1.1
+++ loncom/lonmaxima 2006/03/08 14:22:14 1.14
@@ -3,7 +3,7 @@
# The LearningOnline Network with CAPA
# Connect to MAXIMA CAS
#
-# $Id: lonmaxima,v 1.1 2006/03/03 16:07:34 www Exp $
+# $Id: lonmaxima,v 1.14 2006/03/08 14:22:14 www Exp $
#
# Copyright Michigan State University Board of Trustees
#
@@ -29,49 +29,305 @@
#
# http://www.lon-capa.org/
#
+
use IPC::Open3;
use IO::Select;
-# Scary: cannot use strict!!!
-##### use strict;
+use IO::Socket;
+use IO::File;
+use Symbol;
+use POSIX;
+use Fcntl;
+use Socket;
+use lib '/home/httpd/lib/perl/';
+use LONCAPA::Configuration;
+
+use strict;
-sub maximareply {
- my $cmd=shift;
- my $reply='';
- my $error='';
- my $exitstatus='';
+# global variables
+my $STARTPORT = 5664; # port for first child's server
+my $PREFORK = 5; # number of children to maintain
+my $MAX_CLIENTS_PER_CHILD = 5; # number of clients each child should process
+my %children = (); # keys are current child process IDs
+my %usedmaximaports = (); # keys are the used maximaports
+my $children = 0; # current number of children
+my $status; # string for current status
+my $pidfile; # file containg parent process pid
+my $port; # path to UNIX socket file
+my %perlvar; # configuration file info
+my $lastlog; # last string that was logged
+use vars qw($PREFORK $MAX_CLIENTS_PER_CHILD %children $children %usedmaximaports $status
+ $pidfile $port %perlvar $lastlog);
+
+# ------------------------------------------------------------ Service routines
+sub REAPER { # takes care of dead children
+ # and MAXIMA processes
+ $SIG{CHLD} = \&REAPER;
+ my $pid = wait;
+ $children--;
+ &logthis("Child $pid for port or process $children{$pid} died");
+ delete($usedmaximaports{$children{$pid}});
+ delete($children{$pid});
+}
+
+sub HUNTSMAN { # signal handler for SIGINT
+ local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children
+ kill('INT' => keys(%children));
+ unlink($pidfile);
+ unlink($port);
+ &logthis('---- Shutdown ----');
+ exit; # clean up with dignity
+}
- unless ($cmd=~/\;\n$/) { $cmd.=";\n"; }
- my $pid = open3($cmd_in, $cmd_out, $cmd_err, 'maxima');
-
- $SIG{CHLD} = sub {
- $exitstatus="$? on $pid\n" if waitpid($pid, 0) > 0;
- };
- print $cmd_in $cmd;
- close $cmd_in;
+
+# --------------------------------------------------------------------- Logging
+
+sub logthis {
+ my ($message)=@_;
+ my $execdir=$perlvar{'lonDaemons'};
+ my $fh=IO::File->new(">>$execdir/logs/lonmaxima.log");
+ my $now=time;
+ my $local=localtime($now);
+ $lastlog=$local.': '.$message;
+ print $fh "$local ($$): $message\n";
+}
+
+# -------------------------------------------------------------- Status setting
+
+sub status {
+ my ($what)=@_;
+ my $now=time;
+ my $local=localtime($now);
+ $status=$local.': '.$what;
+ $0='lonmaxima: '.$what.' '.$local;
+}
+
+# -------------------------------------------------------- Escape Special Chars
+
+sub escape {
+ my ($str)=@_;
+ $str =~ s/(\W)/"%".unpack('H2',$1)/eg;
+ return $str;
+}
+
+# ----------------------------------------------------- Un-Escape Special Chars
+
+sub unescape {
+ my ($str)=@_;
+ $str =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg;
+ return $str;
+}
+
+# ------------------------ grabs exception and records it to log before exiting
+sub catchexception {
+ my ($signal)=@_;
+ $SIG{QUIT}='DEFAULT';
+ $SIG{__DIE__}='DEFAULT';
+ chomp($signal);
+ &logthis("<font color=\"red\">CRITICAL: "
+ ."ABNORMAL EXIT. Child $$ died through "
+ ."\"$signal\"</font>");
+ die("Signal abend");
+}
+
+# -------------------------------------------------- make a socket non-blocking
+sub nonblock {
+ my $socket = shift;
+ my $flags;
+ if (ref($socket)) {
+ $flags = fcntl($socket, F_GETFL, 0)
+ or die "Can't get flags for socket: $!\n";
+ fcntl($socket, F_SETFL, $flags | O_NONBLOCK)
+ or die "Can't make socket nonblocking: $!\n";
+ }
+}
+
+# ---------------------------------------------------------------- Main program
+# -------------------------------- Set signal handlers to record abnormal exits
+
+
+$SIG{'QUIT'}=\&catchexception;
+$SIG{__DIE__}=\&catchexception;
+
+# ---------------------------------- Read loncapa_apache.conf and loncapa.conf
+&status("Read loncapa.conf and loncapa_apache.conf");
+%perlvar=%{&LONCAPA::Configuration::read_conf('loncapa.conf')};
+
+# ----------------------------- Make sure this process is running from user=www
+my $wwwid=getpwnam('www');
+if ($wwwid!=$<) {
+ my $emailto="$perlvar{'lonAdmEMail'},$perlvar{'lonSysEMail'}";
+ my $subj="LON: User ID mismatch";
+ system("echo 'User ID mismatch. lonmaxima must be run as user www.' |\
+ mailto $emailto -s '$subj' > /dev/null");
+ exit 1;
+}
+
+# --------------------------------------------- Check if other instance running
+
+$pidfile="$perlvar{'lonDaemons'}/logs/lonmaxima.pid";
+
+if (-e $pidfile) {
+ my $lfh=IO::File->new("$pidfile");
+ my $pide=<$lfh>;
+ chomp($pide);
+ if (kill(0 => $pide)) { die "already running"; }
+}
+
+# ------------------------------------------------------- Listen to UNIX socket
+&status("Opening socket");
+
+$port = "$perlvar{'lonSockDir'}/maximasock";
+
+unlink($port);
+
+
+my $server = IO::Socket::UNIX->new(Local => $port,
+ Type => SOCK_STREAM,
+ Listen => 10 );
+if (!$server) {
+ my $st=120+int(rand(240));
+
+ &logthis("<font color=blue>WARNING: ".
+ "Can't make server socket ($st secs): .. exiting</font>");
- my $selector = IO::Select->new( );
- $selector->add($cmd_err, $cmd_out);
+ sleep($st);
+ exit;
+}
- while (my @ready = $selector->can_read) {
- foreach my $fh (@ready) {
- if (fileno($fh) == fileno($cmd_err)) {
- $error.=<$cmd_err>;
- } else {
- my $line = scalar <$cmd_out>;
- if ($line=~/^(\(\%o|\s)/) {
- $line=~s/^\(.*\)/ /;
- $reply.=$line;
- }
- }
- $selector->remove($fh) if eof($fh);
- }
+
+# ---------------------------------------------------- Fork once and dissociate
+
+my $fpid=fork;
+exit if $fpid;
+die("Couldn't fork: $!") unless defined($fpid);
+
+POSIX::setsid() or die "Can't start new session: $!";
+
+# ------------------------------------------------------- Write our PID on disk
+
+my $execdir=$perlvar{'lonDaemons'};
+open(PIDSAVE,">$execdir/logs/lonmaxima.pid");
+print PIDSAVE "$$\n";
+close(PIDSAVE);
+&logthis("<font color='red'>CRITICAL: ---------- Starting ----------</font>");
+&status('Starting');
+
+
+# Install signal handlers.
+$SIG{CHLD} = \&REAPER;
+$SIG{INT} = $SIG{TERM} = \&HUNTSMAN;
+
+my $maximaport=$STARTPORT;
+# Fork off our children.
+for (1 .. $PREFORK) {
+ &make_new_child($server,$maximaport);
+ $maximaport++;
+}
+
+# And maintain the population.
+while (1) {
+ &status('Parent process, sleeping');
+ sleep; # wait for a signal (i.e., child's death)
+ for (my $i = $children; $i < $PREFORK; $i++) {
+ &status('Parent process, starting child');
+ my $newport;
+ &logthis("Current pool: ".join(', ',keys %usedmaximaports));
+ foreach my $testport ($STARTPORT .. $STARTPORT+$PREFORK-1) {
+ if (!$usedmaximaports{$testport}) { $newport=$testport; }
+ }
+ if ($newport) {
+ &make_new_child($server,$newport); # top up the child pool
+ }
}
- close $cmd_out;
- close $cmd_err;
- return ($reply,$error,$exitstatus);
+}
+
+sub make_new_child {
+ my ($server,$maximaport) = @_;
+
+ # block signal for fork
+ my $sigset = POSIX::SigSet->new(SIGINT);
+ sigprocmask(SIG_BLOCK, $sigset)
+ or die("Can't block SIGINT for fork: $!\n");
+
+ die("fork: $!") unless defined(my $pid = fork);
+
+ if ($pid) {
+ # Parent records the child's birth and returns.
+ sigprocmask(SIG_UNBLOCK, $sigset)
+ or die("Can't unblock SIGINT for fork: $!\n");
+ $children{$pid} = $maximaport;
+ $children++;
+ $usedmaximaports{$maximaport}=1;
+ return;
+ } else {
+ &logthis("Starting child on port $maximaport");
+ # Child can *not* return from this subroutine.
+ $SIG{INT} = 'DEFAULT'; # make SIGINT kill us as it did before
+
+ # unblock signals
+ sigprocmask(SIG_UNBLOCK, $sigset)
+ or die("Can't unblock SIGINT for fork: $!\n");
+
+ # open the MAXIMA port
+ my $maximaserver = IO::Socket::INET->new(LocalPort => $maximaport,
+ Type => SOCK_STREAM,
+ Proto => 'tcp',
+ Reuse => 1,
+ Listen => 10 )
+ or die "making socket: $@\n";
+ &nonblock($maximaserver);
+ my $maximaselect=IO::Select->new($maximaserver);
+ sleep(2);
+
+ # open MAXIMA to talk to that port
+ my ($cmd_in, $cmd_out, $cmd_err);
+ my $maximapid = open3($cmd_in, $cmd_out, $cmd_err, "maxima -s $maximaport");
+ $children{$maximapid} = "Maxima $maximapid port $maximaport";
+ my $prompt=<$cmd_out>;
+ &logthis("Maxima $maximapid: $prompt");
+
+ # hopefully, MAXIMA calls us back
+ &status("Waiting $maximapid on $maximaport");
+ my $maximaclient=$maximaserver->accept();
+ $maximaselect->add($maximaclient);
+ &nonblock($maximaclient);
+ &status("$maximapid on $maximaport connected.");
+ &logthis("Maxima $maximapid on port $maximaport connected.");
+ &logthis('Initial reply: '.&maximareply($maximaselect));
+ # handle connections until we've reached $MAX_CLIENTS_PER_CHILD
+ for (my $i=0; $i < $MAX_CLIENTS_PER_CHILD; $i++) {
+ &status('Accepting connections for '.$maximapid.' on '.$maximaport);
+ my $client = $server->accept() or last;
+ while (my $cmd=<$client>) {
+ &status('Processing command by '.$maximapid.' on '.$maximaport);
+ print $maximaclient &unescape($cmd).";\n";
+ print $client &escape(&maximareply($maximaselect))."\n";
+ }
+ }
+
+ # tidy up gracefully and finish
+
+ if (ref($cmd_out)) { close($cmd_out); }
+ if (ref($cmd_err)) { close($cmd_err); }
+ if (ref($cmd_in)) { close($cmd_in); }
+
+ # this exit is VERY important, otherwise the child will become
+ # a producer of more and more children, forking yourself into
+ # process death.
+ exit;
+ }
+}
+
+sub maximareply {
+ my ($maximaselect)=@_;
+ my $output='';
+ foreach my $ready ($maximaselect->can_read(1)) {
+ my $data = '';
+ my $rv = $ready->recv($data, POSIX::BUFSIZ, 0);
+ $output.=$data;
+ }
+ return $output;
}
-print join("\n----\n",&maximareply('1234'));
-print join("\n----\n",&maximareply('x0: 5;x1: 7;integrate (x^2, x, x0, x1);'));