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