1: #!/usr/bin/perl
2: # The LearningOnline Network with CAPA
3: # lonc maintains the connections to remote computers
4: #
5: # $Id: loncnew,v 1.16 2003/07/29 02:33:05 foxr Exp $
6: #
7: # Copyright Michigan State University Board of Trustees
8: #
9: # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
10: #
11: # LON-CAPA is free software; you can redistribute it and/or modify
12: # it under the terms of the GNU General Public License as published by
13: # the Free Software Foundation; either version 2 of the License, or
14: # (at your option) any later version.
15: #
16: # LON-CAPA is distributed in the hope that it will be useful,
17: # but WITHOUT ANY WARRANTY; without even the implied warranty of
18: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19: # GNU General Public License for more details.
20: #
21: # You should have received a copy of the GNU General Public License
22: # along with LON-CAPA; if not, write to the Free Software
23: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24: #
25: # /home/httpd/html/adm/gpl.txt
26: #
27: # http://www.lon-capa.org/
28: #
29: #
30: # new lonc handles n request out bver m connections to londs.
31: # This module is based on the Event class.
32: # Development iterations:
33: # - Setup basic event loop. (done)
34: # - Add timer dispatch. (done)
35: # - Add ability to accept lonc UNIX domain sockets. (done)
36: # - Add ability to create/negotiate lond connections (done).
37: # - Add general logic for dispatching requests and timeouts. (done).
38: # - Add support for the lonc/lond requests. (done).
39: # - Add logging/status monitoring.
40: # - Add Signal handling - HUP restarts. USR1 status report.
41: # - Add Configuration file I/O (done).
42: # - Add management/status request interface.
43: # - Add deferred request capability. (done)
44: # - Detect transmission timeouts.
45: #
46:
47: # Change log:
48: # $Log: loncnew,v $
49: # Revision 1.16 2003/07/29 02:33:05 foxr
50: # Add SIGINT processing to child processes to toggle annoying trace mode
51: # on/off.. will try to use this to isolate the compute boud process issue.
52: #
53: # Revision 1.15 2003/07/15 02:07:05 foxr
54: # Added code for lonc/lond transaction timeouts. Who knows if it works right.
55: # The intent is for a timeout to fail any transaction in progress and kill
56: # off the sockt that timed out.
57: #
58: # Revision 1.14 2003/07/03 02:10:18 foxr
59: # Get all of the signals to work correctly.
60: #
61: # Revision 1.13 2003/07/02 01:31:55 foxr
62: # Added kill -HUP logic (restart).
63: #
64: # Revision 1.11 2003/06/25 01:54:44 foxr
65: # Fix more problems with transaction failure.
66: #
67: # Revision 1.10 2003/06/24 02:46:04 foxr
68: # Put a limit on the number of times we'll retry a connection.
69: # Start getting the signal stuff put in as well...note that need to get signals
70: # going or else 6the client will permanently give up on dead servers.
71: #
72: # Revision 1.9 2003/06/13 02:38:43 foxr
73: # Add logging in 'expected format'
74: #
75: # Revision 1.8 2003/06/11 02:04:35 foxr
76: # Support delayed transactions... this is done uniformly by encapsulating
77: # transactions in an object ... a LondTransaction that is implemented by
78: # LondTransaction.pm
79: #
80: # Revision 1.7 2003/06/03 01:59:39 foxr
81: # complete coding to support deferred transactions.
82: #
83: #
84:
85: use lib "/home/httpd/lib/perl/";
86: use lib "/home/foxr/newloncapa/types";
87: use Event qw(:DEFAULT );
88: use POSIX qw(:signal_h);
89: use POSIX;
90: use IO::Socket;
91: use IO::Socket::INET;
92: use IO::Socket::UNIX;
93: use IO::File;
94: use IO::Handle;
95: use Socket;
96: use Crypt::IDEA;
97: use LONCAPA::Queue;
98: use LONCAPA::Stack;
99: use LONCAPA::LondConnection;
100: use LONCAPA::LondTransaction;
101: use LONCAPA::Configuration;
102: use LONCAPA::HashIterator;
103:
104:
105: #
106: # Disable all signals we might receive from outside for now.
107: #
108: #$SIG{QUIT} = IGNORE;
109: #$SIG{HUP} = IGNORE;
110: #$SIG{USR1} = IGNORE;
111: #$SIG{INT} = IGNORE;
112: #$SIG{CHLD} = IGNORE;
113: #$SIG{__DIE__} = IGNORE;
114:
115:
116: # Read the httpd configuration file to get perl variables
117: # normally set in apache modules:
118:
119: my $perlvarref = LONCAPA::Configuration::read_conf('loncapa.conf');
120: my %perlvar = %{$perlvarref};
121:
122: #
123: # parent and shared variables.
124:
125: my %ChildHash; # by pid -> host.
126:
127:
128: my $MaxConnectionCount = 10; # Will get from config later.
129: my $ClientConnection = 0; # Uniquifier for client events.
130:
131: my $DebugLevel = 0;
132: my $NextDebugLevel= 10; # So Sigint can toggle this.
133: my $IdleTimeout= 3600; # Wait an hour before pruning connections.
134:
135: #
136: # The variables below are only used by the child processes.
137: #
138: my $RemoteHost; # Name of host child is talking to.
139: my $UnixSocketDir= "/home/httpd/sockets";
140: my $IdleConnections = Stack->new(); # Set of idle connections
141: my %ActiveConnections; # Connections to the remote lond.
142: my %ActiveTransactions; # LondTransactions in flight.
143: my %ActiveClients; # Serial numbers of active clients by socket.
144: my $WorkQueue = Queue->new(); # Queue of pending transactions.
145: my $ConnectionCount = 0;
146: my $IdleSeconds = 0; # Number of seconds idle.
147: my $Status = ""; # Current status string.
148: my $RecentLogEntry = "";
149: my $ConnectionRetries=5; # Number of connection retries allowed.
150: my $ConnectionRetriesLeft=5; # Number of connection retries remaining.
151:
152: #
153: # The hash below gives the HTML format for log messages
154: # given a severity.
155: #
156: my %LogFormats;
157:
158: $LogFormats{"CRITICAL"} = "<font color=red>CRITICAL: %s</font>";
159: $LogFormats{"SUCCESS"} = "<font color=green>SUCCESS: %s</font>";
160: $LogFormats{"INFO"} = "<font color=yellow>INFO: %s</font>";
161: $LogFormats{"WARNING"} = "<font color=blue>WARNING: %s</font>";
162: $LogFormats{"DEFAULT"} = " %s ";
163:
164:
165:
166: =pod
167:
168: =head2 LogPerm
169:
170: Makes an entry into the permanent log file.
171:
172: =cut
173: sub LogPerm {
174: my $message=shift;
175: my $execdir=$perlvar{'lonDaemons'};
176: my $now=time;
177: my $local=localtime($now);
178: my $fh=IO::File->new(">>$execdir/logs/lonnet.perm.log");
179: print $fh "$now:$message:$local\n";
180: }
181:
182: =pod
183:
184: =head2 Log
185:
186: Logs a message to the log file.
187: Parameters:
188:
189: =item severity
190:
191: One of CRITICAL, WARNING, INFO, SUCCESS used to select the
192: format string used to format the message. if the severity is
193: not a defined severity the Default format string is used.
194:
195: =item message
196:
197: The base message. In addtion to the format string, the message
198: will be appended to a string containing the name of our remote
199: host and the time will be formatted into the message.
200:
201: =cut
202:
203: sub Log {
204: my $severity = shift;
205: my $message = shift;
206:
207: if(!$LogFormats{$severity}) {
208: $severity = "DEFAULT";
209: }
210:
211: my $format = $LogFormats{$severity};
212:
213: # Put the window dressing in in front of the message format:
214:
215: my $now = time;
216: my $local = localtime($now);
217: my $finalformat = "$local ($$) [$RemoteHost] [$Status] ";
218: my $finalformat = $finalformat.$format."\n";
219:
220: # open the file and put the result.
221:
222: my $execdir = $perlvar{'lonDaemons'};
223: my $fh = IO::File->new(">>$execdir/logs/lonc.log");
224: my $msg = sprintf($finalformat, $message);
225: $RecentLogEntry = $msg;
226: print $fh $msg;
227:
228:
229: }
230:
231:
232: =pod
233:
234: =head2 GetPeerName
235:
236: Returns the name of the host that a socket object is connected to.
237:
238: =cut
239:
240: sub GetPeername {
241: my $connection = shift;
242: my $AdrFamily = shift;
243: my $peer = $connection->peername();
244: my $peerport;
245: my $peerip;
246: if($AdrFamily == AF_INET) {
247: ($peerport, $peerip) = sockaddr_in($peer);
248: my $peername = gethostbyaddr($iaddr, $AdrFamily);
249: return $peername;
250: } elsif ($AdrFamily == AF_UNIX) {
251: my $peerfile;
252: ($peerfile) = sockaddr_un($peer);
253: return $peerfile;
254: }
255: }
256: #----------------------------- Timer management ------------------------
257: =pod
258:
259: =head2 Debug
260:
261: Invoked to issue a debug message.
262:
263: =cut
264:
265: sub Debug {
266: my $level = shift;
267: my $message = shift;
268: if ($level <= $DebugLevel) {
269: Log("INFO", "-Debug- $message host = $RemotHost");
270: }
271: }
272:
273: sub SocketDump {
274: my $level = shift;
275: my $socket= shift;
276: if($level <= $DebugLevel) {
277: $socket->Dump();
278: }
279: }
280:
281: =pod
282:
283: =head2 ShowStatus
284:
285: Place some text as our pid status.
286: and as what we return in a SIGUSR1
287:
288: =cut
289: sub ShowStatus {
290: my $state = shift;
291: my $now = time;
292: my $local = localtime($now);
293: $Status = $local.": ".$state;
294: $0='lonc: '.$state.' '.$local;
295: }
296:
297: =pod
298:
299: =head 2 SocketTimeout
300:
301: Called when an action on the socket times out. The socket is
302: destroyed and any active transaction is failed.
303:
304:
305: =cut
306: sub SocketTimeout {
307: my $Socket = shift;
308:
309: KillSocket($Socket);
310: }
311:
312: =pod
313:
314: =head2 Tick
315:
316: Invoked each timer tick.
317:
318: =cut
319:
320:
321: sub Tick {
322: my $client;
323: ShowStatus(GetServerHost()." Connection count: ".$ConnectionCount);
324:
325: # Is it time to prune connection count:
326:
327:
328: if($IdleConnections->Count() &&
329: ($WorkQueue->Count() == 0)) { # Idle connections and nothing to do?
330: $IdleSeconds++;
331: if($IdleSeconds > $IdleTimeout) { # Prune a connection...
332: $Socket = $IdleConnections->pop();
333: KillSocket($Socket);
334: }
335: } else {
336: $IdleSeconds = 0; # Reset idle count if not idle.
337: }
338: #
339: # For each inflight transaction, tick down its timeout counter.
340: #
341: foreach $item (keys %ActiveTransactions) {
342: my $Socket = $ActiveTransactions{$item}->getServer();
343: $Socket->Tick();
344: }
345: # Do we have work in the queue, but no connections to service them?
346: # If so, try to make some new connections to get things going again.
347: #
348:
349: my $Requests = $WorkQueue->Count();
350: if (($ConnectionCount == 0) && ($Requests > 0)) {
351: if ($ConnectionRetriesLeft > 0) {
352: my $Connections = ($Requests <= $MaxConnectionCount) ?
353: $Requests : $MaxConnectionCount;
354: Debug(1,"Work but no connections, start ".$Connections." of them");
355: for ($i =0; $i < $Connections; $i++) {
356: MakeLondConnection();
357: }
358: } else {
359: Debug(1,"Work in queue, but gave up on connections..flushing\n");
360: EmptyQueue(); # Connections can't be established.
361: }
362:
363: }
364: }
365:
366: =pod
367:
368: =head2 SetupTimer
369:
370: Sets up a 1 per sec recurring timer event. The event handler is used to:
371:
372: =item
373:
374: Trigger timeouts on communications along active sockets.
375:
376: =item
377:
378: Trigger disconnections of idle sockets.
379:
380: =cut
381:
382: sub SetupTimer {
383: Debug(6, "SetupTimer");
384: Event->timer(interval => 1, debug => 1, cb => \&Tick );
385: }
386:
387: =pod
388:
389: =head2 ServerToIdle
390:
391: This function is called when a connection to the server is
392: ready for more work.
393:
394: If there is work in the Work queue the top element is dequeued
395: and the connection will start to work on it. If the work queue is
396: empty, the connection is pushed on the idle connection stack where
397: it will either get another work unit, or alternatively, if it sits there
398: long enough, it will be shut down and released.
399:
400: =cut
401:
402: sub ServerToIdle {
403: my $Socket = shift; # Get the socket.
404: delete($ActiveTransactions{$Socket}); # Server has no transaction
405:
406: &Debug(6, "Server to idle");
407:
408: # If there's work to do, start the transaction:
409:
410: $reqdata = $WorkQueue->dequeue(); # This is a LondTransaction
411: unless($reqdata eq undef) {
412: Debug(9, "Queue gave request data: ".$reqdata->getRequest());
413: &StartRequest($Socket, $reqdata);
414:
415: } else {
416:
417: # There's no work waiting, so push the server to idle list.
418: &Debug(8, "No new work requests, server connection going idle");
419: $IdleConnections->push($Socket);
420: }
421: }
422:
423: =pod
424:
425: =head2 ClientWritable
426:
427: Event callback for when a client socket is writable.
428:
429: This callback is established when a transaction reponse is
430: avaiable from lond. The response is forwarded to the unix socket
431: as it becomes writable in this sub.
432:
433: Parameters:
434:
435: =item Event
436:
437: The event that has been triggered. Event->w->data is
438: the data and Event->w->fd is the socket to write.
439:
440: =cut
441:
442: sub ClientWritable {
443: my $Event = shift;
444: my $Watcher = $Event->w;
445: my $Data = $Watcher->data;
446: my $Socket = $Watcher->fd;
447:
448: # Try to send the data:
449:
450: &Debug(6, "ClientWritable writing".$Data);
451: &Debug(9, "Socket is: ".$Socket);
452:
453: if($Socket->connected) {
454: my $result = $Socket->send($Data, 0);
455:
456: # $result undefined: the write failed.
457: # otherwise $result is the number of bytes written.
458: # Remove that preceding string from the data.
459: # If the resulting data is empty, destroy the watcher
460: # and set up a read event handler to accept the next
461: # request.
462:
463: &Debug(9,"Send result is ".$result." Defined: ".defined($result));
464: if(defined($result)) {
465: &Debug(9, "send result was defined");
466: if($result == length($Data)) { # Entire string sent.
467: &Debug(9, "ClientWritable data all written");
468: $Watcher->cancel();
469: #
470: # Set up to read next request from socket:
471:
472: my $descr = sprintf("Connection to lonc client %d",
473: $ActiveClients{$Socket});
474: Event->io(cb => \&ClientRequest,
475: poll => 'r',
476: desc => $descr,
477: data => "",
478: fd => $Socket);
479:
480: } else { # Partial string sent.
481: $Watcher->data(substr($Data, $result));
482: if($result == 0) { # client hung up on us!!
483: Log("INFO", "lonc pipe client hung up on us!");
484: $Watcher->cancel;
485: $Socket->shutdown(2);
486: $Socket->close();
487: }
488: }
489:
490: } else { # Error of some sort...
491:
492: # Some errnos are possible:
493: my $errno = $!;
494: if($errno == POSIX::EWOULDBLOCK ||
495: $errno == POSIX::EAGAIN ||
496: $errno == POSIX::EINTR) {
497: # No action taken?
498: } else { # Unanticipated errno.
499: &Debug(5,"ClientWritable error or peer shutdown".$RemoteHost);
500: $Watcher->cancel; # Stop the watcher.
501: $Socket->shutdown(2); # Kill connection
502: $Socket->close(); # Close the socket.
503: }
504:
505: }
506: } else {
507: $Watcher->cancel(); # A delayed request...just cancel.
508: }
509: }
510:
511: =pod
512:
513: =head2 CompleteTransaction
514:
515: Called when the reply data has been received for a lond
516: transaction. The reply data must now be sent to the
517: ultimate client on the other end of the Unix socket. This is
518: done by setting up a writable event for the socket with the
519: data the reply data.
520:
521: Parameters:
522:
523: =item Socket
524:
525: Socket on which the lond transaction occured. This is a
526: LondConnection. The data received is in the TransactionReply member.
527:
528: =item Transaction
529:
530: The transaction that is being completed.
531:
532: =cut
533:
534: sub CompleteTransaction {
535: &Debug(6,"Complete transaction");
536: my $Socket = shift;
537: my $Transaction = shift;
538:
539: if (!$Transaction->isDeferred()) { # Normal transaction
540: my $data = $Socket->GetReply(); # Data to send.
541: StartClientReply($Transaction, $data);
542: } else { # Delete deferred transaction file.
543: Log("SUCCESS", "A delayed transaction was completed");
544: LogPerm("S:$Client:".$Transaction->getRequest());
545: unlink $Transaction->getFile();
546: }
547: }
548: =pod
549: =head1 StartClientReply
550:
551: Initiates a reply to a client where the reply data is a parameter.
552:
553: =head2 parameters:
554:
555: =item Transaction
556:
557: The transaction for which we are responding to the client.
558:
559: =item data
560:
561: The data to send to apached client.
562:
563: =cut
564: sub StartClientReply {
565: my $Transaction = shift;
566: my $data = shift;
567:
568:
569: my $Client = $Transaction->getClient();
570:
571: &Debug(8," Reply was: ".$data);
572: my $Serial = $ActiveClients{$Client};
573: my $desc = sprintf("Connection to lonc client %d",
574:
575: $Serial);
576: Event->io(fd => $Client,
577: poll => "w",
578: desc => $desc,
579: cb => \&ClientWritable,
580: data => $data);
581: }
582: =pod
583: =head2 FailTransaction
584:
585: Finishes a transaction with failure because the associated lond socket
586: disconnected. There are two possibilities:
587: - The transaction is deferred: in which case we just quietly
588: delete the transaction since there is no client connection.
589: - The transaction is 'live' in which case we initiate the sending
590: of "con_lost" to the client.
591:
592: Deleting the transaction means killing it from the
593: %ActiveTransactions hash.
594:
595: Parameters:
596:
597: =item client
598:
599: The LondTransaction we are failing.
600:
601: =cut
602:
603: sub FailTransaction {
604: my $transaction = shift;
605: Debug(1, "Failing transaction: ".$transaction->getRequest());
606: if (!$transaction->isDeferred()) { # If the transaction is deferred we'll get to it.
607: my $client = $transaction->getClient();
608: Debug(1," Replying con_lost to ".$transaction->getRequest());
609: StartClientReply($transaction, "con_lost\n");
610: }
611:
612: }
613:
614: =pod
615: =head1 EmptyQueue
616:
617: Fails all items in the work queue with con_lost.
618: Note that each item in the work queue is a transaction.
619:
620: =cut
621: sub EmptyQueue {
622: while($WorkQueue->Count()) {
623: my $request = $WorkQueue->dequeue(); # This is a transaction
624: FailTransaction($request);
625: }
626: }
627:
628: =pod
629:
630: =head2 CloseAllLondConnections
631:
632: Close all connections open on lond prior to exit e.g.
633:
634: =cut
635: sub CloseAllLondConnections {
636: foreach $Socket (keys %ActiveConnections) {
637: KillSocket($Socket);
638: }
639: }
640: =cut
641:
642: =pod
643:
644: =head2 KillSocket
645:
646: Destroys a socket. This function can be called either when a socket
647: has died of 'natural' causes or because a socket needs to be pruned due to
648: idleness. If the socket has died naturally, if there are no longer any
649: live connections a new connection is created (in case there are transactions
650: in the queue). If the socket has been pruned, it is never re-created.
651:
652: Parameters:
653:
654: =item Socket
655:
656: The socket to kill off.
657:
658: =item Restart
659:
660: nonzero if we are allowed to create a new connection.
661:
662:
663: =cut
664: sub KillSocket {
665: my $Socket = shift;
666:
667: $Socket->Shutdown();
668:
669: # If the socket came from the active connection set,
670: # delete its transaction... note that FailTransaction should
671: # already have been called!!!
672: # otherwise it came from the idle set.
673: #
674:
675: if(exists($ActiveTransactions{$Socket})) {
676: delete ($ActiveTransactions{$Socket});
677: }
678: if(exists($ActiveConnections{$Socket})) {
679: delete($ActiveConnections{$Socket});
680: }
681: $ConnectionCount--;
682:
683: # If the connection count has gone to zero and there is work in the
684: # work queue, the work all gets failed with con_lost.
685: #
686: if($ConnectionCount == 0) {
687: EmptyQueue;
688: }
689: }
690:
691: =pod
692:
693: =head2 LondReadable
694:
695: This function is called whenever a lond connection
696: is readable. The action is state dependent:
697:
698: =head3 State=Initialized
699:
700: We''re waiting for the challenge, this is a no-op until the
701: state changes.
702:
703: =head3 State=Challenged
704:
705: The challenge has arrived we need to transition to Writable.
706: The connection must echo the challenge back.
707:
708: =head3 State=ChallengeReplied
709:
710: The challenge has been replied to. The we are receiveing the
711: 'ok' from the partner.
712:
713: =head3 State=RequestingKey
714:
715: The ok has been received and we need to send the request for
716: an encryption key. Transition to writable for that.
717:
718: =head3 State=ReceivingKey
719:
720: The the key has been requested, now we are reading the new key.
721:
722: =head3 State=Idle
723:
724: The encryption key has been negotiated or we have finished
725: reading data from the a transaction. If the callback data has
726: a client as well as the socket iformation, then we are
727: doing a transaction and the data received is relayed to the client
728: before the socket is put on the idle list.
729:
730: =head3 State=SendingRequest
731:
732: I do not think this state can be received here, but if it is,
733: the appropriate thing to do is to transition to writable, and send
734: the request.
735:
736: =head3 State=ReceivingReply
737:
738: We finished sending the request to the server and now transition
739: to readable to receive the reply.
740:
741: The parameter to this function are:
742:
743: The event. Implicit in this is the watcher and its data. The data
744: contains at least the lond connection object and, if a
745: transaction is in progress, the socket attached to the local client.
746:
747: =cut
748:
749: sub LondReadable {
750:
751: my $Event = shift;
752: my $Watcher = $Event->w;
753: my $Socket = $Watcher->data;
754: my $client = undef;
755:
756: &Debug(6,"LondReadable called state = ".$State);
757:
758:
759: my $State = $Socket->GetState(); # All action depends on the state.
760:
761: SocketDump(6, $Socket);
762: my $status = $Socket->Readable();
763: &Debug(2, "Socket->Readable returned: $status");
764:
765: if($status != 0) {
766: # bad return from socket read. Currently this means that
767: # The socket has become disconnected. We fail the transaction.
768:
769: if(exists($ActiveTransactions{$Socket})) {
770: Debug(3,"Lond connection lost failing transaction");
771: FailTransaction($ActiveTransactions{$Socket});
772: }
773: $Watcher->cancel();
774: KillSocket($Socket);
775: return;
776: }
777: SocketDump(6,$Socket);
778:
779: $State = $Socket->GetState(); # Update in case of transition.
780: &Debug(6, "After read, state is ".$State);
781:
782: if($State eq "Initialized") {
783:
784:
785: } elsif ($State eq "ChallengeReceived") {
786: # The challenge must be echoed back; The state machine
787: # in the connection takes care of setting that up. Just
788: # need to transition to writable:
789:
790: $Watcher->cb(\&LondWritable);
791: $Watcher->poll("w");
792:
793: } elsif ($State eq "ChallengeReplied") {
794:
795:
796: } elsif ($State eq "RequestingKey") {
797: # The ok was received. Now we need to request the key
798: # That requires us to be writable:
799:
800: $Watcher->cb(\&LondWritable);
801: $Watcher->poll("w");
802:
803: } elsif ($State eq "ReceivingKey") {
804:
805: } elsif ($State eq "Idle") {
806: # If necessary, complete a transaction and then go into the
807: # idle queue.
808: $Watcher->cancel();
809: if(exists($ActiveTransactions{$Socket})) {
810: Debug(8,"Completing transaction!!");
811: CompleteTransaction($Socket,
812: $ActiveTransactions{$Socket});
813: } else {
814: Log("SUCCESS", "Connection ".$ConnectionCount." to "
815: .$RemoteHost." now ready for action");
816: }
817: ServerToIdle($Socket); # Next work unit or idle.
818:
819: } elsif ($State eq "SendingRequest") {
820: # We need to be writable for this and probably don't belong
821: # here inthe first place.
822:
823: Deubg(6, "SendingRequest state encountered in readable");
824: $Watcher->poll("w");
825: $Watcher->cb(\&LondWritable);
826:
827: } elsif ($State eq "ReceivingReply") {
828:
829:
830: } else {
831: # Invalid state.
832: Debug(4, "Invalid state in LondReadable");
833: }
834: }
835:
836: =pod
837:
838: =head2 LondWritable
839:
840: This function is called whenever a lond connection
841: becomes writable while there is a writeable monitoring
842: event. The action taken is very state dependent:
843:
844: =head3 State = Connected
845:
846: The connection is in the process of sending the 'init' hailing to the
847: lond on the remote end. The connection object''s Writable member is
848: called. On error, ConnectionError is called to destroy the connection
849: and remove it from the ActiveConnections hash
850:
851: =head3 Initialized
852:
853: 'init' has been sent, writability monitoring is removed and
854: readability monitoring is started with LondReadable as the callback.
855:
856: =head3 ChallengeReceived
857:
858: The connection has received the who are you challenge from the remote
859: system, and is in the process of sending the challenge
860: response. Writable is called.
861:
862: =head3 ChallengeReplied
863:
864: The connection has replied to the initial challenge The we switch to
865: monitoring readability looking for the server to reply with 'ok'.
866:
867: =head3 RequestingKey
868:
869: The connection is in the process of requesting its encryption key.
870: Writable is called.
871:
872: =head3 ReceivingKey
873:
874: The connection has sent the request for a key. Switch to readability
875: monitoring to accept the key
876:
877: =head3 SendingRequest
878:
879: The connection is in the process of sending a request to the server.
880: This request is part of a client transaction. All the states until
881: now represent the client setup protocol. Writable is called.
882:
883: =head3 ReceivingReply
884:
885: The connection has sent a request. Now it must receive a reply.
886: Readability monitoring is requested.
887:
888: This function is an event handler and therefore receives as
889: a parameter the event that has fired. The data for the watcher
890: of this event is a reference to a list of one or two elements,
891: depending on state. The first (and possibly only) element is the
892: socket. The second (present only if a request is in progress)
893: is the socket on which to return a reply to the caller.
894:
895: =cut
896:
897: sub LondWritable {
898: my $Event = shift;
899: my $Watcher = $Event->w;
900: my $Socket = $Watcher->data;
901: my $State = $Socket->GetState();
902:
903: Debug(6,"LondWritable State = ".$State."\n");
904:
905:
906: # Figure out what to do depending on the state of the socket:
907:
908:
909:
910:
911: SocketDump(6,$Socket);
912:
913: if ($State eq "Connected") {
914:
915: if ($Socket->Writable() != 0) {
916: # The write resulted in an error.
917: # We'll treat this as if the socket got disconnected:
918: Log("WARNING", "Connection to ".$RemoteHost.
919: " has been disconnected");
920: $Watcher->cancel();
921: KillSocket($Socket);
922: return;
923: }
924: # "init" is being sent...
925:
926:
927: } elsif ($State eq "Initialized") {
928:
929: # Now that init was sent, we switch
930: # to watching for readability:
931:
932: $Watcher->cb(\&LondReadable);
933: $Watcher->poll("r");
934:
935: } elsif ($State eq "ChallengeReceived") {
936: # We received the challenge, now we
937: # are echoing it back. This is a no-op,
938: # we're waiting for the state to change
939:
940: if($Socket->Writable() != 0) {
941:
942: $Watcher->cancel();
943: KillSocket($Socket);
944: return;
945: }
946:
947: } elsif ($State eq "ChallengeReplied") {
948: # The echo was sent back, so we switch
949: # to watching readability.
950:
951: $Watcher->cb(\&LondReadable);
952: $Watcher->poll("r");
953:
954: } elsif ($State eq "RequestingKey") {
955: # At this time we're requesting the key.
956: # again, this is essentially a no-op.
957: # we'll write the next chunk until the
958: # state changes.
959:
960: if($Socket->Writable() != 0) {
961: # Write resulted in an error.
962:
963: $Watcher->cancel();
964: KillSocket($Socket);
965: return;
966:
967: }
968: } elsif ($State eq "ReceivingKey") {
969: # Now we need to wait for the key
970: # to come back from the peer:
971:
972: $Watcher->cb(\&LondReadable);
973: $Watcher->poll("r");
974:
975: } elsif ($State eq "SendingRequest") {
976: # At this time we are sending a request to the
977: # peer... write the next chunk:
978:
979: if($Socket->Writable() != 0) {
980:
981: if(exists($ActiveTransactions{$Socket})) {
982: Debug(3, "Lond connection lost, failing transactions");
983: FailTransaction($ActiveTransactions{$Socket});
984: }
985: $Watcher->cancel();
986: KillSocket($Socket);
987: return;
988:
989: }
990:
991: } elsif ($State eq "ReceivingReply") {
992: # The send has completed. Wait for the
993: # data to come in for a reply.
994: Debug(8,"Writable sent request/receiving reply");
995: $Watcher->cb(\&LondReadable);
996: $Watcher->poll("r");
997:
998: } else {
999: # Control only passes here on an error:
1000: # the socket state does not match any
1001: # of the known states... so an error
1002: # must be logged.
1003:
1004: &Debug(4, "Invalid socket state ".$State."\n");
1005: }
1006:
1007: }
1008: =pod
1009:
1010: =cut
1011: sub QueueDelayed {
1012: Debug(3,"QueueDelayed called");
1013:
1014: my $path = "$perlvar{'lonSockDir'}/delayed";
1015:
1016: Debug(4, "Delayed path: ".$path);
1017: opendir(DIRHANDLE, $path);
1018:
1019: @alldelayed = grep /\.$RemoteHost$/, readdir DIRHANDLE;
1020: Debug(4, "Got ".$alldelayed." delayed files");
1021: closedir(DIRHANDLE);
1022: my $dfname;
1023: my $reqfile;
1024: foreach $dfname (sort @alldelayed) {
1025: $reqfile = "$path/$dfname";
1026: Debug(4, "queueing ".$reqfile);
1027: my $Handle = IO::File->new($reqfile);
1028: my $cmd = <$Handle>;
1029: chomp $cmd; # There may or may not be a newline...
1030: $cmd = $cmd."\n"; # now for sure there's exactly one newline.
1031: my $Transaction = LondTransaction->new($cmd);
1032: $Transaction->SetDeferred($reqfile);
1033: QueueTransaction($Transaction);
1034: }
1035:
1036: }
1037:
1038: =pod
1039:
1040: =head2 MakeLondConnection
1041:
1042: Create a new lond connection object, and start it towards its initial
1043: idleness. Once idle, it becomes elligible to receive transactions
1044: from the work queue. If the work queue is not empty when the
1045: connection is completed and becomes idle, it will dequeue an entry and
1046: start off on it.
1047:
1048: =cut
1049:
1050: sub MakeLondConnection {
1051: Debug(4,"MakeLondConnection to ".GetServerHost()." on port "
1052: .GetServerPort());
1053:
1054: my $Connection = LondConnection->new(&GetServerHost(),
1055: &GetServerPort());
1056:
1057: if($Connection == undef) { # Needs to be more robust later.
1058: Log("CRITICAL","Failed to make a connection with lond.");
1059: $ConnectionRetriesLeft--;
1060: return 0; # Failure.
1061: } else {
1062: $ConnectionRetriesLeft = $ConnectionRetries; # success resets the count
1063: # The connection needs to have writability
1064: # monitored in order to send the init sequence
1065: # that starts the whole authentication/key
1066: # exchange underway.
1067: #
1068: my $Socket = $Connection->GetSocket();
1069: if($Socket == undef) {
1070: die "did not get a socket from the connection";
1071: } else {
1072: &Debug(9,"MakeLondConnection got socket: ".$Socket);
1073: }
1074:
1075:
1076: $event = Event->io(fd => $Socket,
1077: poll => 'w',
1078: cb => \&LondWritable,
1079: data => $Connection,
1080: desc => 'Connection to lond server');
1081: $ActiveConnections{$Connection} = $event;
1082:
1083: $ConnectionCount++;
1084: Debug(4, "Connection count = ".$ConnectionCount);
1085: if($ConnectionCount == 1) { # First Connection:
1086: QueueDelayed;
1087: }
1088: Log("SUCESS", "Created connection ".$ConnectionCount
1089: ." to host ".GetServerHost());
1090: return 1; # Return success.
1091: }
1092:
1093: }
1094:
1095: =pod
1096:
1097: =head2 StartRequest
1098:
1099: Starts a lond request going on a specified lond connection.
1100: parameters are:
1101:
1102: =item $Lond
1103:
1104: Connection to the lond that will send the transaction and receive the
1105: reply.
1106:
1107: =item $Client
1108:
1109: Connection to the client that is making this request We got the
1110: request from this socket, and when the request has been relayed to
1111: lond and we get a reply back from lond it will get sent to this
1112: socket.
1113:
1114: =item $Request
1115:
1116: The text of the request to send.
1117:
1118: =cut
1119:
1120: sub StartRequest {
1121: my $Lond = shift;
1122: my $Request = shift; # This is a LondTransaction.
1123:
1124: Debug(6, "StartRequest: ".$Request->getRequest());
1125:
1126: my $Socket = $Lond->GetSocket();
1127:
1128: $Request->Activate($Lond);
1129: $ActiveTransactions{$Lond} = $Request;
1130:
1131: $Lond->InitiateTransaction($Request->getRequest());
1132: $event = Event->io(fd => $Socket,
1133: poll => "w",
1134: cb => \&LondWritable,
1135: data => $Lond,
1136: desc => "lond transaction connection");
1137: $ActiveConnections{$Lond} = $event;
1138: Debug(8," Start Request made watcher data with ".$event->data."\n");
1139: }
1140:
1141: =pod
1142:
1143: =head2 QueueTransaction
1144:
1145: If there is an idle lond connection, it is put to work doing this
1146: transaction. Otherwise, the transaction is placed in the work queue.
1147: If placed in the work queue and the maximum number of connections has
1148: not yet been created, a new connection will be started. Our goal is
1149: to eventually have a sufficient number of connections that the work
1150: queue will typically be empty. parameters are:
1151:
1152: =item Socket
1153:
1154: open on the lonc client.
1155:
1156: =item Request
1157:
1158: data to send to the lond.
1159:
1160: =cut
1161:
1162: sub QueueTransaction {
1163:
1164: my $requestData = shift; # This is a LondTransaction.
1165: my $cmd = $requestData->getRequest();
1166:
1167: Debug(6,"QueueTransaction: ".$cmd);
1168:
1169: my $LondSocket = $IdleConnections->pop();
1170: if(!defined $LondSocket) { # Need to queue request.
1171: Debug(8,"Must queue...");
1172: $WorkQueue->enqueue($requestData);
1173: if($ConnectionCount < $MaxConnectionCount) {
1174: Debug(4,"Starting additional lond connection");
1175: MakeLondConnection();
1176: }
1177: } else { # Can start the request:
1178: Debug(8,"Can start...");
1179: StartRequest($LondSocket, $requestData);
1180: }
1181: }
1182:
1183: #-------------------------- Lonc UNIX socket handling ---------------------
1184:
1185: =pod
1186:
1187: =head2 ClientRequest
1188: Callback that is called when data can be read from the UNIX domain
1189: socket connecting us with an apache server process.
1190:
1191: =cut
1192:
1193: sub ClientRequest {
1194: Debug(6, "ClientRequest");
1195: my $event = shift;
1196: my $watcher = $event->w;
1197: my $socket = $watcher->fd;
1198: my $data = $watcher->data;
1199: my $thisread;
1200:
1201: Debug(9, " Watcher named: ".$watcher->desc);
1202:
1203: my $rv = $socket->recv($thisread, POSIX::BUFSIZ, 0);
1204: Debug(8, "rcv: data length = ".length($thisread)
1205: ." read =".$thisread);
1206: unless (defined $rv && length($thisread)) {
1207: # Likely eof on socket.
1208: Debug(5,"Client Socket closed on lonc for ".$RemoteHost);
1209: close($socket);
1210: $watcher->cancel();
1211: delete($ActiveClients{$socket});
1212: return;
1213: }
1214: Debug(8,"Data: ".$data." this read: ".$thisread);
1215: $data = $data.$thisread; # Append new data.
1216: $watcher->data($data);
1217: if($data =~ /(.*\n)/) { # Request entirely read.
1218: if($data eq "close_connection_exit\n") {
1219: Log("CRITICAL",
1220: "Request Close Connection ... exiting");
1221: CloseAllLondConnections();
1222: exit;
1223: }
1224: Debug(8, "Complete transaction received: ".$data);
1225: my $Transaction = LondTransaction->new($data);
1226: $Transaction->SetClient($socket);
1227: QueueTransaction($Transaction);
1228: $watcher->cancel(); # Done looking for input data.
1229: }
1230:
1231: }
1232:
1233:
1234: =pod
1235:
1236: =head2 NewClient
1237:
1238: Callback that is called when a connection is received on the unix
1239: socket for a new client of lonc. The callback is parameterized by the
1240: event.. which is a-priori assumed to be an io event, and therefore has
1241: an fd member that is the Listener socket. We Accept the connection
1242: and register a new event on the readability of that socket:
1243:
1244: =cut
1245:
1246: sub NewClient {
1247: Debug(6, "NewClient");
1248: my $event = shift; # Get the event parameters.
1249: my $watcher = $event->w;
1250: my $socket = $watcher->fd; # Get the event' socket.
1251: my $connection = $socket->accept(); # Accept the client connection.
1252: Debug(8,"Connection request accepted from "
1253: .GetPeername($connection, AF_UNIX));
1254:
1255:
1256: my $description = sprintf("Connection to lonc client %d",
1257: $ClientConnection);
1258: Debug(9, "Creating event named: ".$description);
1259: Event->io(cb => \&ClientRequest,
1260: poll => 'r',
1261: desc => $description,
1262: data => "",
1263: fd => $connection);
1264: $ActiveClients{$connection} = $ClientConnection;
1265: $ClientConnection++;
1266: }
1267:
1268: =pod
1269:
1270: =head2 GetLoncSocketPath
1271:
1272: Returns the name of the UNIX socket on which to listen for client
1273: connections.
1274:
1275: =cut
1276:
1277: sub GetLoncSocketPath {
1278: return $UnixSocketDir."/".GetServerHost();
1279: }
1280:
1281: =pod
1282:
1283: =head2 GetServerHost
1284:
1285: Returns the host whose lond we talk with.
1286:
1287: =cut
1288:
1289: sub GetServerHost {
1290: return $RemoteHost; # Setup by the fork.
1291: }
1292:
1293: =pod
1294:
1295: =head2 GetServerPort
1296:
1297: Returns the lond port number.
1298:
1299: =cut
1300:
1301: sub GetServerPort {
1302: return $perlvar{londPort};
1303: }
1304:
1305: =pod
1306:
1307: =head2 SetupLoncListener
1308:
1309: Setup a lonc listener event. The event is called when the socket
1310: becomes readable.. that corresponds to the receipt of a new
1311: connection. The event handler established will accept the connection
1312: (creating a communcations channel), that int turn will establish
1313: another event handler to subess requests.
1314:
1315: =cut
1316:
1317: sub SetupLoncListener {
1318:
1319: my $socket;
1320: my $SocketName = GetLoncSocketPath();
1321: unlink($SocketName);
1322: unless ($socket =IO::Socket::UNIX->new(Local => $SocketName,
1323: Listen => 10,
1324: Type => SOCK_STREAM)) {
1325: die "Failed to create a lonc listner socket";
1326: }
1327: Event->io(cb => \&NewClient,
1328: poll => 'r',
1329: desc => 'Lonc listener Unix Socket',
1330: fd => $socket);
1331: }
1332:
1333: =pod
1334:
1335: =head2 ChildStatus
1336:
1337: Child USR1 signal handler to report the most recent status
1338: into the status file.
1339:
1340: =cut
1341: sub ChildStatus {
1342: my $event = shift;
1343: my $watcher = $event->w;
1344:
1345: Debug(2, "Reporting child status because : ".$watcher->data);
1346: my $docdir = $perlvar{'lonDocRoot'};
1347: my $fh = IO::File->new(">>$docdir/lon-status/loncstatus.txt");
1348: print $fh $$."\t".$RemoteHost."\t".$Status."\t".
1349: $RecentLogEntry."\n";
1350: }
1351:
1352: =pod
1353:
1354: =head2 SignalledToDeath
1355:
1356: Called in response to a signal that causes a chid process to die.
1357:
1358: =cut
1359:
1360:
1361: sub SignalledToDeath {
1362: my $event = shift;
1363: my $watcher= $event->w;
1364:
1365: Debug(2,"Signalled to death! via ".$watcher->data);
1366: my ($signal) = @_;
1367: chomp($signal);
1368: Log("CRITICAL", "Abnormal exit. Child $$ for $RemoteHost "
1369: ."died through "."\"$signal\"");
1370: LogPerm("F:lonc: $$ on $RemoteHost signalled to death: "
1371: ."\"$signal\"");
1372: die("Signal abnormal end");
1373: exit 0;
1374:
1375: }
1376:
1377: =head2 ToggleDebug
1378:
1379: This sub toggles trace debugging on and off.
1380:
1381: =cut
1382:
1383: sub ToggleDebug {
1384: my $Current = $DebugLevel;
1385: $DebugLevel = $NextDebugLevel;
1386: $NextDebugLevel = $Current;
1387:
1388: Log("SUCCESS", "New debugging level for $RemoteHost now $DebugLevel");
1389:
1390: }
1391:
1392: =head2 ChildProcess
1393:
1394: This sub implements a child process for a single lonc daemon.
1395:
1396: =cut
1397:
1398: sub ChildProcess {
1399:
1400:
1401: #
1402: # Signals must be handled by the Event framework...
1403: #
1404:
1405: Event->signal(signal => "QUIT",
1406: cb => \&SignalledToDeath,
1407: data => "QUIT");
1408: Event->signal(signal => "HUP",
1409: cb => \&ChildStatus,
1410: data => "HUP");
1411: Event->signal(signal => "USR1",
1412: cb => \&ChildStatus,
1413: data => "USR1");
1414: Event->signal(signal => "INT",
1415: cb => \&ToggleDebug,
1416: data => "INT");
1417:
1418: SetupTimer();
1419:
1420: SetupLoncListener();
1421:
1422: $Event::Debuglevel = $DebugLevel;
1423:
1424: Debug(9, "Making initial lond connection for ".$RemoteHost);
1425:
1426: # Setup the initial server connection:
1427:
1428: # &MakeLondConnection(); // let first work requirest do it.
1429:
1430:
1431: Debug(9,"Entering event loop");
1432: my $ret = Event::loop(); # Start the main event loop.
1433:
1434:
1435: die "Main event loop exited!!!";
1436: }
1437:
1438: # Create a new child for host passed in:
1439:
1440: sub CreateChild {
1441: my $sigset = POSIX::SigSet->new(SIGINT);
1442: sigprocmask(SIG_BLOCK, $sigset);
1443: my $host = shift;
1444: $RemoteHost = $host;
1445: Log("CRITICAL", "Forking server for ".$host);
1446: $pid = fork;
1447: if($pid) { # Parent
1448: $ChildHash{$pid} = $RemoteHost;
1449: sigprocmask(SIG_UNBLOCK, $sigset);
1450:
1451: } else { # child.
1452: ShowStatus("Connected to ".$RemoteHost);
1453: $SIG{INT} = DEFAULT;
1454: sigprocmask(SIG_UNBLOCK, $sigset);
1455: ChildProcess; # Does not return.
1456: }
1457:
1458: }
1459: #
1460: # Parent process logic pass 1:
1461: # For each entry in the hosts table, we will
1462: # fork off an instance of ChildProcess to service the transactions
1463: # to that host. Each pid will be entered in a global hash
1464: # with the value of the key, the host.
1465: # The parent will then enter a loop to wait for process exits.
1466: # Each exit gets logged and the child gets restarted.
1467: #
1468:
1469: #
1470: # Fork and start in new session so hang-up isn't going to
1471: # happen without intent.
1472: #
1473:
1474:
1475:
1476:
1477:
1478:
1479: ShowStatus("Forming new session");
1480: my $childpid = fork;
1481: if ($childpid != 0) {
1482: sleep 4; # Give child a chacne to break to
1483: exit 0; # a new sesion.
1484: }
1485: #
1486: # Write my pid into the pid file so I can be located
1487: #
1488:
1489: ShowStatus("Parent writing pid file:");
1490: $execdir = $perlvar{'lonDaemons'};
1491: open (PIDSAVE, ">$execdir/logs/lonc.pid");
1492: print PIDSAVE "$$\n";
1493: close(PIDSAVE);
1494:
1495: if (POSIX::setsid() < 0) {
1496: print "Could not create new session\n";
1497: exit -1;
1498: }
1499:
1500: ShowStatus("Forking node servers");
1501:
1502: Log("CRITICAL", "--------------- Starting children ---------------");
1503:
1504: my $HostIterator = LondConnection::GetHostIterator;
1505: while (! $HostIterator->end()) {
1506:
1507: $hostentryref = $HostIterator->get();
1508: CreateChild($hostentryref->[0]);
1509: $HostIterator->next();
1510: }
1511: $RemoteHost = "Parent Server";
1512:
1513: # Maintain the population:
1514:
1515: ShowStatus("Parent keeping the flock");
1516:
1517: #
1518: # Set up parent signals:
1519: #
1520:
1521: $SIG{INT} = \&Terminate;
1522: $SIG{TERM} = \&Terminate;
1523: $SIG{HUP} = \&Restart;
1524: $SIG{USR1} = \&CheckKids;
1525:
1526: while(1) {
1527: $deadchild = wait();
1528: if(exists $ChildHash{$deadchild}) { # need to restart.
1529: $deadhost = $ChildHash{$deadchild};
1530: delete($ChildHash{$deadchild});
1531: Log("WARNING","Lost child pid= ".$deadchild.
1532: "Connected to host ".$deadhost);
1533: Log("INFO", "Restarting child procesing ".$deadhost);
1534: CreateChild($deadhost);
1535: }
1536: }
1537:
1538:
1539:
1540: =pod
1541:
1542: =head1 CheckKids
1543:
1544: Since kids do not die as easily in this implementation
1545: as the previous one, there is no need to restart the
1546: dead ones (all dead kids get restarted when they die!!)
1547: The only thing this function does is to pass USR1 to the
1548: kids so that they report their status.
1549:
1550: =cut
1551:
1552: sub CheckKids {
1553: Debug(2, "Checking status of children");
1554: my $docdir = $perlvar{'lonDocRoot'};
1555: my $fh = IO::File->new(">$docdir/lon-status/loncstatus.txt");
1556: my $now=time;
1557: my $local=localtime($now);
1558: print $fh "LONC status $local - parent $$ \n\n";
1559: foreach $pid (keys %ChildHash) {
1560: Debug(2, "Sending USR1 -> $pid");
1561: kill 'USR1' => $pid; # Tell Child to report status.
1562: sleep 1; # Wait so file doesn't intermix.
1563: }
1564: }
1565:
1566: =pod
1567:
1568: =head1 Restart
1569:
1570: Signal handler for HUP... all children are killed and
1571: we self restart. This is an el-cheapo way to re read
1572: the config file.
1573:
1574: =cut
1575:
1576: sub Restart {
1577: KillThemAll; # First kill all the children.
1578: Log("CRITICAL", "Restarting");
1579: my $execdir = $perlvar{'lonDaemons'};
1580: unlink("$execdir/logs/lonc.pid");
1581: exec("$execdir/lonc");
1582: }
1583:
1584: =pod
1585:
1586: =head1 KillThemAll
1587:
1588: Signal handler that kills all children by sending them a
1589: SIGINT. Responds to sigint and sigterm.
1590:
1591: =cut
1592:
1593: sub KillThemAll {
1594: Debug(2, "Kill them all!!");
1595: local($SIG{CHLD}) = 'IGNORE'; # Our children >will< die.
1596: foreach $pid (keys %ChildHash) {
1597: my $serving = $ChildHash{$pid};
1598: Debug(2, "Killing lonc for $serving pid = $pid");
1599: ShowStatus("Killing lonc for $serving pid = $pid");
1600: Log("CRITICAL", "Killing lonc for $serving pid = $pid");
1601: kill('INT', $pid);
1602: delete($ChildeHash{$pid});
1603: }
1604: my $execdir = $perlvar{'lonDaemons'};
1605: unlink("$execdir/logs/lonc.pid");
1606: ShowStatus("Killing the master process");
1607: Log("CRITICAL", "Killing the master process.");
1608: }
1609:
1610: =pod
1611:
1612: =head1 Terminate
1613:
1614: Terminate the system.
1615:
1616: =cut
1617:
1618: sub Terminate {
1619: KillThemAll;
1620: exit;
1621:
1622: }
1623: =pod
1624:
1625: =head1 Theory
1626:
1627: The event class is used to build this as a single process with an
1628: event driven model. The following events are handled:
1629:
1630: =item UNIX Socket connection Received
1631:
1632: =item Request data arrives on UNIX data transfer socket.
1633:
1634: =item lond connection becomes writable.
1635:
1636: =item timer fires at 1 second intervals.
1637:
1638: All sockets are run in non-blocking mode. Timeouts managed by the timer
1639: handler prevents hung connections.
1640:
1641: Key data structures:
1642:
1643: =item RequestQueue
1644:
1645: A queue of requests received from UNIX sockets that are
1646: waiting for a chance to be forwarded on a lond connection socket.
1647:
1648: =item ActiveConnections
1649:
1650: A hash of lond connections that have transactions in process that are
1651: available to be timed out.
1652:
1653: =item ActiveTransactions
1654:
1655: A hash indexed by lond connections that contain the client reply
1656: socket for each connection that has an active transaction on it.
1657:
1658: =item IdleConnections
1659:
1660: A hash of lond connections that have no work to do. These connections
1661: can be closed if they are idle for a long enough time.
1662:
1663: =cut
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