--- loncom/Attic/lonc 2000/12/06 20:38:21 1.12 +++ loncom/Attic/lonc 2002/03/03 18:13:07 1.31 @@ -5,6 +5,30 @@ # provides persistent TCP connections to the other servers in the network # through multiplexed domain sockets # +# $Id: lonc,v 1.31 2002/03/03 18:13:07 harris41 Exp $ +# +# Copyright Michigan State University Board of Trustees +# +# This file is part of the LearningOnline Network with CAPA (LON-CAPA). +# +# LON-CAPA is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 2 of the License, or +# (at your option) any later version. +# +# LON-CAPA is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with LON-CAPA; if not, write to the Free Software +# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA +# +# /home/httpd/html/adm/gpl.txt +# +# http://www.lon-capa.org/ +# # PID in subdir logs/lonc.pid # kill kills # HUP restarts @@ -15,6 +39,12 @@ # 2/8,7/25 Gerd Kortemeyer # 12/05 Scott Harrison # 12/05 Gerd Kortemeyer +# YEAR=2001 +# 01/10/01 Scott Harrison +# 03/14/01,03/15,06/12,11/26,11/27,11/28 Gerd Kortemeyer +# 12/20 Scott Harrison +# YEAR=2002 +# 2/19/02,02/22/02,02/25/02 Gerd Kortemeyer # # based on nonforker from Perl Cookbook # - server who multiplexes without forking @@ -27,27 +57,21 @@ use Socket; use Fcntl; use Tie::RefHash; use Crypt::IDEA; +use Net::Ping; +use LWP::UserAgent(); -# grabs exception and records it to log before exiting -sub catchexception { - my ($signal)=@_; - $SIG{'QUIT'}='DEFAULT'; - $SIG{__DIE__}='DEFAULT'; - &logthis("CRITICAL: " - ."ABNORMAL EXIT. Child $$ for server $wasserver died through " - ."\"$signal\" with this parameter->[$@]"); - die($@); -} - -$childmaxattempts=10; +$status=''; +$lastlog=''; +$conserver='SHELL'; # -------------------------------- Set signal handlers to record abnormal exits -$SIG{'QUIT'}=\&catchexception; +&status("Init exception handlers"); +$SIG{QUIT}=\&catchexception; $SIG{__DIE__}=\&catchexception; # ------------------------------------ Read httpd access.conf and get variables - +&status("Read access.conf"); open (CONFIG,"/etc/httpd/conf/access.conf") || die "Can't read access.conf"; while ($configline=) { @@ -59,6 +83,17 @@ while ($configline=) { } close(CONFIG); +# ----------------------------- Make sure this process is running from user=www +&status("Check user ID"); +my $wwwid=getpwnam('www'); +if ($wwwid!=$<) { + $emailto="$perlvar{'lonAdmEMail'},$perlvar{'lonSysEMail'}"; + $subj="LON: $perlvar{'lonHostID'} User ID mismatch"; + system("echo 'User ID mismatch. lonc must be run as user www.' |\ + mailto $emailto -s '$subj' > /dev/null"); + exit 1; +} + # --------------------------------------------- Check if other instance running my $pidfile="$perlvar{'lonDaemons'}/logs/lonc.pid"; @@ -77,8 +112,12 @@ open (CONFIG,"$perlvar{'lonTabDir'}/host while ($configline=) { my ($id,$domain,$role,$name,$ip)=split(/:/,$configline); chomp($ip); - $hostip{$id}=$ip; + if ($ip) { + $hostip{$id}=$ip; + $hostname{$id}=$name; + } } + close(CONFIG); # -------------------------------------------------------- Routines for forking @@ -90,96 +129,20 @@ close(CONFIG); %childatt = (); # number of attempts to start server # for ID -sub REAPER { # takes care of dead children - $SIG{CHLD} = \&REAPER; - my $pid = wait; - my $wasserver=$children{$pid}; - &logthis("CRITICAL: " - ."Child $pid for server $wasserver died ($childatt{$wasserver})"); - delete $children{$pid}; - delete $childpid{$wasserver}; - my $port = "$perlvar{'lonSockDir'}/$wasserver"; - unlink($port); -} - -sub HUNTSMAN { # signal handler for SIGINT - local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children - kill 'INT' => keys %children; - my $execdir=$perlvar{'lonDaemons'}; - unlink("$execdir/logs/lonc.pid"); - &logthis("CRITICAL: Shutting down"); - exit; # clean up with dignity -} - -sub HUPSMAN { # signal handler for SIGHUP - local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children - kill 'INT' => keys %children; - &logthis("CRITICAL: Restarting"); - unlink("$execdir/logs/lonc.pid"); - my $execdir=$perlvar{'lonDaemons'}; - exec("$execdir/lonc"); # here we go again -} - -sub USRMAN { - &logthis("USR1: Trying to establish connections again"); - foreach $thisserver (keys %hostip) { - $answer=subreply("ping",$thisserver); - &logthis("USR1: Ping $thisserver " - ."(pid >$childpid{$thisserver}<, $childatt{thisserver} attempts): " - ." >$answer<"); - } - %childatt=(); -} - -# -------------------------------------------------- Non-critical communication -sub subreply { - my ($cmd,$server)=@_; - my $answer=''; - if ($server ne $perlvar{'lonHostID'}) { - my $peerfile="$perlvar{'lonSockDir'}/$server"; - my $sclient=IO::Socket::UNIX->new(Peer =>"$peerfile", - Type => SOCK_STREAM, - Timeout => 10) - or return "con_lost"; - print $sclient "$cmd\n"; - my $answer=<$sclient>; - chomp($answer); - if (!$answer) { $answer="con_lost"; } - } else { $answer='self_reply'; } - return $answer; -} - -# --------------------------------------------------------------------- Logging - -sub logthis { - my $message=shift; - my $execdir=$perlvar{'lonDaemons'}; - my $fh=IO::File->new(">>$execdir/logs/lonc.log"); - my $now=time; - my $local=localtime($now); - print $fh "$local ($$): $message\n"; -} - - -sub logperm { - my $message=shift; - my $execdir=$perlvar{'lonDaemons'}; - my $now=time; - my $local=localtime($now); - my $fh=IO::File->new(">>$execdir/logs/lonnet.perm.log"); - print $fh "$now:$message:$local\n"; -} +$childmaxattempts=5; # ---------------------------------------------------- Fork once and dissociate - +&status("Fork and dissociate"); $fpid=fork; exit if $fpid; die "Couldn't fork: $!" unless defined ($fpid); POSIX::setsid() or die "Can't start new session: $!"; -# ------------------------------------------------------- Write our PID on disk +$conserver='PARENT'; +# ------------------------------------------------------- Write our PID on disk +&status("Write PID"); $execdir=$perlvar{'lonDaemons'}; open (PIDSAVE,">$execdir/logs/lonc.pid"); print PIDSAVE "$$\n"; @@ -192,8 +155,12 @@ $SIG{HUP}=$SIG{USR1}='IGNORE'; # Fork off our children, one for every server +&status("Forking ..."); + foreach $thisserver (keys %hostip) { - make_new_child($thisserver); + if (&online($hostname{$thisserver})) { + make_new_child($thisserver); + } } &logthis("Done starting initial servers"); @@ -206,28 +173,38 @@ $SIG{USR1} = \&USRMAN; # And maintain the population. while (1) { + &status("Sleeping"); sleep; # wait for a signal (i.e., child's death) # See who died and start new one + &status("Woke up"); + my $skipping=''; foreach $thisserver (keys %hostip) { if (!$childpid{$thisserver}) { - if ($childatt{$thisserver}<=$childmaxattempts) { + if (($childatt{$thisserver}<$childmaxattempts) && + (&online($hostname{$thisserver}))) { $childatt{$thisserver}++; &logthis( "INFO: Trying to reconnect for $thisserver " ."($childatt{$thisserver} of $childmaxattempts attempts)"); make_new_child($thisserver); - } + } else { + $skipping.=$thisserver.' '; + } + } } + if ($skipping) { + &logthis("WARNING: Skipped $skipping"); + } } sub make_new_child { - my $conserver=shift; + $newserver=shift; my $pid; my $sigset; - &logthis("Attempting to start child for server $conserver"); + &logthis("Attempting to start child for server $newserver"); # block signal for fork $sigset = POSIX::SigSet->new(SIGINT); sigprocmask(SIG_BLOCK, $sigset) @@ -239,13 +216,15 @@ sub make_new_child { # Parent records the child's birth and returns. sigprocmask(SIG_UNBLOCK, $sigset) or die "Can't unblock SIGINT for fork: $!\n"; - $children{$pid} = $conserver; + $children{$pid} = $newserver; $childpid{$conserver} = $pid; return; } else { + $conserver=$newserver; # Child can *not* return from this subroutine. $SIG{INT} = 'DEFAULT'; # make SIGINT kill us as it did before - + $SIG{USR1}= \&logstatus; + # unblock signals sigprocmask(SIG_UNBLOCK, $sigset) or die "Can't unblock SIGINT for fork: $!\n"; @@ -255,64 +234,23 @@ sub make_new_child { $port = "$perlvar{'lonSockDir'}/$conserver"; unlink($port); -# ---------------------------------------------------- Client to network server -unless ( - $remotesock = IO::Socket::INET->new(PeerAddr => $hostip{$conserver}, - PeerPort => $perlvar{'londPort'}, - Proto => "tcp", - Type => SOCK_STREAM) - ) { - my $st=120+int(rand(240)); - &logthis( -"WARNING: Couldn't connect $conserver ($st secs): $@"); - sleep($st); - exit; - }; -# --------------------------------------- Send a ping to make other end do USR1 -print $remotesock "init\n"; -$answer=<$remotesock>; -print $remotesock "$answer"; -$answer=<$remotesock>; -chomp($answer); -&logthis("Init reply for $conserver: >$answer<"); -sleep 5; -print $remotesock "pong\n"; -$answer=<$remotesock>; -chomp($answer); -&logthis("Pong reply for $conserver: >$answer<"); -# ----------------------------------------------------------- Initialize cipher -print $remotesock "ekey\n"; -my $buildkey=<$remotesock>; -my $key=$conserver.$perlvar{'lonHostID'}; -$key=~tr/a-z/A-Z/; -$key=~tr/G-P/0-9/; -$key=~tr/Q-Z/0-9/; -$key=$key.$buildkey.$key.$buildkey.$key.$buildkey; -$key=substr($key,0,32); -my $cipherkey=pack("H32",$key); -if ($cipher=new IDEA $cipherkey) { - &logthis("Secure connection initialized: $conserver"); -} else { - my $st=120+int(rand(240)); - &logthis( - "WARNING: ". - "Could not establish secure connection, $conserver ($st secs)!"); - sleep($st); - exit; -} +# -------------------------------------------------------------- Open other end -# ----------------------------------------- We're online, send delayed messages +&openremote($conserver); +# ----------------------------------------- We're online, send delayed messages + &status("Checking for delayed messages"); my @allbuffered; my $path="$perlvar{'lonSockDir'}/delayed"; opendir(DIRHANDLE,$path); @allbuffered=grep /\.$conserver$/, readdir DIRHANDLE; closedir(DIRHANDLE); my $dfname; - map { + foreach (@allbuffered) { + &status("Sending delayed: $_"); $dfname="$path/$_"; - &logthis($dfname); + &logthis('Sending '.$dfname); my $wcmd; { my $dfh=IO::File->new($dfname); @@ -333,18 +271,27 @@ if ($cipher=new IDEA $cipherkey) { } $cmd="enc:$cmdlength:$encrequest\n"; } - + $SIG{ALRM}=sub { die "timeout" }; + $SIG{__DIE__}='DEFAULT'; + eval { + alarm(60); print $remotesock "$cmd\n"; $answer=<$remotesock>; chomp($answer); - if ($answer ne '') { + alarm(0); + }; + $SIG{ALRM}='DEFAULT'; + $SIG{__DIE__}=\&catchexception; + + if (($answer ne '') && ($@!~/timeout/)) { unlink("$dfname"); - &logthis("Delayed $cmd to $conserver: >$answer<"); + &logthis("Delayed $cmd: >$answer<"); &logperm("S:$conserver:$bcmd"); } - } @allbuffered; + } # ------------------------------------------------------- Listen to UNIX socket +&status("Opening socket"); unless ( $server = IO::Socket::UNIX->new(Local => $port, Type => SOCK_STREAM, @@ -353,7 +300,7 @@ unless ( my $st=120+int(rand(240)); &logthis( "WARNING: ". - "Can't make server socket $conserver ($st secs): $@"); + "Can't make server socket ($st secs): $@"); sleep($st); exit; }; @@ -382,11 +329,11 @@ while (1) { # check for new information on the connections we have # anything to read or accept? - foreach $client ($select->can_read(1)) { + foreach $client ($select->can_read(0.1)) { if ($client == $server) { # accept a new connection - + &status("Accept new connection: $conserver"); $client = $server->accept(); $select->add($client); nonblock($client); @@ -401,6 +348,7 @@ while (1) { delete $outbuffer{$client}; delete $ready{$client}; + &status("Idle"); $select->remove($client); close $client; next; @@ -429,18 +377,25 @@ while (1) { next unless exists $outbuffer{$client}; $rv = $client->send($outbuffer{$client}, 0); + + unless ($outbuffer{$client} eq "con_lost\n") { unless (defined $rv) { # Whine, but move on. - warn "I was told I could write, but I can't.\n"; + &logthis("I was told I could write, but I can't.\n"); next; } + $errno=$!; if (($rv == length $outbuffer{$client}) || - ($! == POSIX::EWOULDBLOCK)) { + ($errno == POSIX::EWOULDBLOCK) || ($errno == 0)) { substr($outbuffer{$client}, 0, $rv) = ''; delete $outbuffer{$client} unless length $outbuffer{$client}; } else { # Couldn't write all the data, and it wasn't because # it would have blocked. Shutdown and move on. + + &logthis("Dropping data with ".$errno.": ". + length($outbuffer{$client}).", $rv"); + delete $inbuffer{$client}; delete $outbuffer{$client}; delete $ready{$client}; @@ -449,7 +404,17 @@ while (1) { close($client); next; } + } else { +# -------------------------------------------------------- Wow, connection lost + &logthis( + "CRITICAL: Closing connection"); + &status("Connection lost"); + $remotesock->shutdown(2); + &logthis("Attempting to open new connection"); + &openremote($conserver); + } } + } } @@ -466,6 +431,15 @@ sub handle { # ============================================================= Process request # $request is the text of the request # put text of reply into $outbuffer{$client} +# ------------------------------------------------------------ Is this the end? + if ($request eq "close_connection_exit\n") { + &status("Request close connection"); + &logthis( + "CRITICAL: Request Close Connection"); + $remotesock->shutdown(2); + $server->close(); + exit; + } # ----------------------------------------------------------------------------- if ($request =~ /^encrypt\:/) { my $cmd=$request; @@ -480,8 +454,27 @@ sub handle { } $request="enc:$cmdlength:$encrequest\n"; } +# --------------------------------------------------------------- Main exchange + $SIG{ALRM}=sub { die "timeout" }; + $SIG{__DIE__}='DEFAULT'; + eval { + alarm(300); + &status("Sending: $request"); print $remotesock "$request"; + &status("Waiting for reply from $conserver: $request"); $answer=<$remotesock>; + &status("Received reply: $request"); + alarm(0); + }; + if ($@=~/timeout/) { + $answer=''; + &logthis( + "CRITICAL: Timeout: $request"); + } + $SIG{ALRM}='DEFAULT'; + $SIG{__DIE__}=\&catchexception; + + if ($answer) { if ($answer =~ /^enc/) { my ($cmd,$cmdlength,$encinput)=split(/:/,$answer); @@ -500,6 +493,8 @@ sub handle { $outbuffer{$client} .= "con_lost\n"; } + &status("Completed: $request"); + # ===================================================== Done processing request } delete $ready{$client}; @@ -520,3 +515,418 @@ sub nonblock { or die "Can't make socket nonblocking: $!\n"; } + +sub openremote { +# ---------------------------------------------------- Client to network server + + my $conserver=shift; + +&status("Opening TCP"); + +unless ( + $remotesock = IO::Socket::INET->new(PeerAddr => $hostip{$conserver}, + PeerPort => $perlvar{'londPort'}, + Proto => "tcp", + Type => SOCK_STREAM) + ) { + my $st=120+int(rand(240)); + &logthis( +"WARNING: Couldn't connect ($st secs): $@"); + sleep($st); + exit; + }; +# ----------------------------------------------------------------- Init dialog + +&status("Init dialogue: $conserver"); + + $SIG{ALRM}=sub { die "timeout" }; + $SIG{__DIE__}='DEFAULT'; + eval { + alarm(60); +print $remotesock "init\n"; +$answer=<$remotesock>; +print $remotesock "$answer"; +$answer=<$remotesock>; +chomp($answer); + alarm(0); + }; + $SIG{ALRM}='DEFAULT'; + $SIG{__DIE__}=\&catchexception; + + if ($@=~/timeout/) { + &logthis("Timed out during init"); + exit; + } + +if ($answer ne 'ok') { + &logthis("Init reply: >$answer<"); + my $st=120+int(rand(240)); + &logthis( +"WARNING: Init failed ($st secs)"); + sleep($st); + exit; +} + +sleep 5; +&status("Ponging"); +print $remotesock "pong\n"; +$answer=<$remotesock>; +chomp($answer); +if ($answer!~/^$conserver/) { + &logthis("Pong reply: >$answer<"); +} +# ----------------------------------------------------------- Initialize cipher + +&status("Initialize cipher"); +print $remotesock "ekey\n"; +my $buildkey=<$remotesock>; +my $key=$conserver.$perlvar{'lonHostID'}; +$key=~tr/a-z/A-Z/; +$key=~tr/G-P/0-9/; +$key=~tr/Q-Z/0-9/; +$key=$key.$buildkey.$key.$buildkey.$key.$buildkey; +$key=substr($key,0,32); +my $cipherkey=pack("H32",$key); +if ($cipher=new IDEA $cipherkey) { + &logthis("Secure connection initialized"); +} else { + my $st=120+int(rand(240)); + &logthis( + "WARNING: ". + "Could not establish secure connection ($st secs)!"); + sleep($st); + exit; +} + +} + + + +# grabs exception and records it to log before exiting +sub catchexception { + my ($signal)=@_; + $SIG{QUIT}='DEFAULT'; + $SIG{__DIE__}='DEFAULT'; + chomp($signal); + &logthis("CRITICAL: " + ."ABNORMAL EXIT. Child $$ for server [$wasserver] died through " + ."\"$signal\" with parameter [$@]"); + die($@); +} + +# -------------------------------------- Routines to see if other box available + +sub online { + my $host=shift; + &status("Pinging ".$host); + my $p=Net::Ping->new("tcp",20); + my $online=$p->ping("$host"); + $p->close(); + undef ($p); + return $online; +} + +sub connected { + my ($local,$remote)=@_; + &status("Checking connection $local to $remote"); + $local=~s/\W//g; + $remote=~s/\W//g; + + unless ($hostname{$local}) { return 'local_unknown'; } + unless ($hostname{$remote}) { return 'remote_unknown'; } + + unless (&online($hostname{$local})) { return 'local_offline'; } + + my $ua=new LWP::UserAgent; + + my $request=new HTTP::Request('GET', + "http://".$hostname{$local}.'/cgi-bin/ping.pl?'.$remote); + + my $response=$ua->request($request); + + unless ($response->is_success) { return 'local_error'; } + + my $reply=$response->content; + $reply=(split("\n",$reply))[0]; + $reply=~s/\W//g; + if ($reply ne $remote) { return $reply; } + return 'ok'; +} + + +sub REAPER { # takes care of dead children + $SIG{CHLD} = \&REAPER; + my $pid = wait; + my $wasserver=$children{$pid}; + &logthis("CRITICAL: " + ."Child $pid for server $wasserver died ($childatt{$wasserver})"); + delete $children{$pid}; + delete $childpid{$wasserver}; + my $port = "$perlvar{'lonSockDir'}/$wasserver"; + unlink($port); +} + +sub hangup { + foreach (keys %children) { + $wasserver=$children{$_}; + &status("Closing $wasserver"); + &logthis('Closing '.$wasserver.': '.&subreply('exit',$wasserver)); + &status("Kill PID $_ for $wasserver"); + kill ('INT',$_); + } +} + +sub HUNTSMAN { # signal handler for SIGINT + local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children + &hangup(); + my $execdir=$perlvar{'lonDaemons'}; + unlink("$execdir/logs/lonc.pid"); + &logthis("CRITICAL: Shutting down"); + exit; # clean up with dignity +} + +sub HUPSMAN { # signal handler for SIGHUP + local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children + &hangup(); + &logthis("CRITICAL: Restarting"); + unlink("$execdir/logs/lonc.pid"); + my $execdir=$perlvar{'lonDaemons'}; + exec("$execdir/lonc"); # here we go again +} + +sub checkchildren { + &initnewstatus(); + &logstatus(); + &logthis('Going to check on the children'); + foreach (sort keys %children) { + sleep 1; + unless (kill 'USR1' => $_) { + &logthis ('CRITICAL: Child '.$_.' is dead'); + &logstatus($$.' is dead'); + } + } +} + +sub USRMAN { + &logthis("USR1: Trying to establish connections again"); + %childatt=(); + &checkchildren(); +} + +# -------------------------------------------------- Non-critical communication +sub subreply { + my ($cmd,$server)=@_; + my $answer=''; + if ($server ne $perlvar{'lonHostID'}) { + my $peerfile="$perlvar{'lonSockDir'}/$server"; + my $sclient=IO::Socket::UNIX->new(Peer =>"$peerfile", + Type => SOCK_STREAM, + Timeout => 10) + or return "con_lost"; + + + $SIG{ALRM}=sub { die "timeout" }; + $SIG{__DIE__}='DEFAULT'; + eval { + alarm(10); + print $sclient "$cmd\n"; + $answer=<$sclient>; + chomp($answer); + alarm(0); + }; + if ((!$answer) || ($@=~/timeout/)) { $answer="con_lost"; } + $SIG{ALRM}='DEFAULT'; + $SIG{__DIE__}=\&catchexception; + } else { $answer='self_reply'; } + return $answer; +} + +# --------------------------------------------------------------------- Logging + +sub logthis { + my $message=shift; + my $execdir=$perlvar{'lonDaemons'}; + my $fh=IO::File->new(">>$execdir/logs/lonc.log"); + my $now=time; + my $local=localtime($now); + $lastlog=$local.': '.$message; + print $fh "$local ($$) [$conserver] [$status]: $message\n"; +} + + +sub logperm { + my $message=shift; + my $execdir=$perlvar{'lonDaemons'}; + my $now=time; + my $local=localtime($now); + my $fh=IO::File->new(">>$execdir/logs/lonnet.perm.log"); + print $fh "$now:$message:$local\n"; +} +# ------------------------------------------------------------------ Log status + +sub logstatus { + my $docdir=$perlvar{'lonDocRoot'}; + my $fh=IO::File->new(">>$docdir/lon-status/loncstatus.txt"); + print $fh $$."\t".$conserver."\t".$status."\t".$lastlog."\n"; +} + +sub initnewstatus { + my $docdir=$perlvar{'lonDocRoot'}; + my $fh=IO::File->new(">$docdir/lon-status/loncstatus.txt"); + my $now=time; + my $local=localtime($now); + print $fh "LONC status $local - parent $$\n\n"; +} + +# -------------------------------------------------------------- Status setting + +sub status { + my $what=shift; + my $now=time; + my $local=localtime($now); + $status=$local.': '.$what; +} + + + +# ----------------------------------- POD (plain old documentation, CPAN style) + +=head1 NAME + +lonc - LON TCP-MySQL-Server Daemon for handling database requests. + +=head1 SYNOPSIS + +Usage: B + +Should only be run as user=www. This is a command-line script which +is invoked by B. There is no expectation that a typical user +will manually start B from the command-line. (In other words, +DO NOT START B YOURSELF.) + +=head1 DESCRIPTION + +Provides persistent TCP connections to the other servers in the network +through multiplexed domain sockets + +B forks off children processes that correspond to the other servers +in the network. Management of these processes can be done at the +parent process level or the child process level. + +B is the location of log messages. + +The process management is now explained in terms of linux shell commands, +subroutines internal to this code, and signal assignments: + +=over 4 + +=item * + +PID is stored in B + +This is the process id number of the parent B process. + +=item * + +SIGTERM and SIGINT + +Parent signal assignment: + $SIG{INT} = $SIG{TERM} = \&HUNTSMAN; + +Child signal assignment: + $SIG{INT} = 'DEFAULT'; (and SIGTERM is DEFAULT also) +(The child dies and a SIGALRM is sent to parent, awaking parent from slumber + to restart a new child.) + +Command-line invocations: + B B<-s> SIGTERM I + B B<-s> SIGINT I + +Subroutine B: + This is only invoked for the B parent I. +This kills all the children, and then the parent. +The B file is cleared. + +=item * + +SIGHUP + +Current bug: + This signal can only be processed the first time +on the parent process. Subsequent SIGHUP signals +have no effect. + +Parent signal assignment: + $SIG{HUP} = \&HUPSMAN; + +Child signal assignment: + none (nothing happens) + +Command-line invocations: + B B<-s> SIGHUP I + +Subroutine B: + This is only invoked for the B parent I, +This kills all the children, and then the parent. +The B file is cleared. + +=item * + +SIGUSR1 + +Parent signal assignment: + $SIG{USR1} = \&USRMAN; + +Child signal assignment: + $SIG{USR1}= \&logstatus; + +Command-line invocations: + B B<-s> SIGUSR1 I + +Subroutine B: + When invoked for the B parent I, +SIGUSR1 is sent to all the children, and the status of +each connection is logged. + +=item * + +SIGCHLD + +Parent signal assignment: + $SIG{CHLD} = \&REAPER; + +Child signal assignment: + none + +Command-line invocations: + B B<-s> SIGCHLD I + +Subroutine B: + This is only invoked for the B parent I. +Information pertaining to the child is removed. +The socket port is cleaned up. + +=back + +=head1 PREREQUISITES + +POSIX +IO::Socket +IO::Select +IO::File +Socket +Fcntl +Tie::RefHash +Crypt::IDEA + +=head1 COREQUISITES + +=head1 OSNAMES + +linux + +=head1 SCRIPT CATEGORIES + +Server/Process + +=cut