nsdl/lonsql - view

File: [LON-CAPA] / nsdl / lonsql
Revision 1.2: download - view: text, annotated - select for diffs
Thu Nov 17 22:04:47 2005 UTC (18 years, 5 months ago) by www
Branches: MAIN
CVS tags: HEAD

Removing database stuff

1: #!/usr/bin/perl 2: 3: # The LearningOnline Network 4: # lonsql - LON TCP-NSDL Query Handler. 5: # 6: # $Id: lonsql,v 1.2 2005/11/17 22:04:47 www Exp $ 7: # 8: # Copyright Michigan State University Board of Trustees 9: # 10: # This file is part of the LearningOnline Network with CAPA (LON-CAPA). 11: # 12: # LON-CAPA is free software; you can redistribute it and/or modify 13: # it under the terms of the GNU General Public License as published by 14: # the Free Software Foundation; either version 2 of the License, or 15: # (at your option) any later version. 16: # 17: # LON-CAPA is distributed in the hope that it will be useful, 18: # but WITHOUT ANY WARRANTY; without even the implied warranty of 19: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20: # GNU General Public License for more details. 21: # 22: # You should have received a copy of the GNU General Public License 23: # along with LON-CAPA; if not, write to the Free Software 24: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 25: # 26: # /home/httpd/html/adm/gpl.txt 27: # 28: # http://www.lon-capa.org/ 29: # 30: 31: =pod 32: 33: =head1 NAME 34: 35: lonsql - LON TCP-MySQL-Server Daemon for handling database requests. 36: 37: =head1 SYNOPSIS 38: 39: This script should be run as user=www. 40: Note that a lonsql.pid file contains the pid of the parent process. 41: 42: =head1 OVERVIEW 43: 44: =head2 Purpose within LON-CAPA 45: 46: LON-CAPA is meant to distribute A LOT of educational content to A LOT 47: of people. It is ineffective to directly rely on contents within the 48: ext2 filesystem to be speedily scanned for on-the-fly searches of 49: content descriptions. (Simply put, it takes a cumbersome amount of 50: time to open, read, analyze, and close thousands of files.) 51: 52: The solution is to index various data fields that are descriptive of 53: the educational resources on a LON-CAPA server machine in a 54: database. Descriptive data fields are referred to as "metadata". The 55: question then arises as to how this metadata is handled in terms of 56: the rest of the LON-CAPA network without burdening client and daemon 57: processes. 58: 59: The obvious solution, using lonc to send a query to a lond process, 60: doesn't work so well in general as you can see in the following 61: example: 62: 63: lonc= loncapa client process A-lonc= a lonc process on Server A 64: lond= loncapa daemon process 65: 66: database command 67: A-lonc --------TCP/IP----------------> B-lond 68: 69: The problem emerges that A-lonc and B-lond are kept waiting for the 70: MySQL server to "do its stuff", or in other words, perform the 71: conceivably sophisticated, data-intensive, time-sucking database 72: transaction. By tying up a lonc and lond process, this significantly 73: cripples the capabilities of LON-CAPA servers. 74: 75: The solution is to offload the work onto another process, and use 76: lonc and lond just for requests and notifications of completed 77: processing: 78: 79: database command 80: 81: A-lonc ---------TCP/IP-----------------> B-lond =====> B-lonsql 82: <---------------------------------/ | 83: "ok, I'll get back to you..." | 84: | 85: / 86: A-lond <------------------------------- B-lonc <====== 87: "Guess what? I have the result!" 88: 89: Of course, depending on success or failure, the messages may vary, but 90: the principle remains the same where a separate pool of children 91: processes (lonsql's) handle the MySQL database manipulations. 92: 93: Thus, lonc and lond spend effectively no time waiting on results from 94: the database. 95: 96: =head1 Internals 97: 98: =over 4 99: 100: =cut 101: 102: use strict; 103: 104: use lib '/home/httpd/lib/perl/'; 105: use LONCAPA::Configuration; 106: use LONCAPA::lonmetadata(); 107: 108: use IO::Socket; 109: use Symbol; 110: use POSIX; 111: use IO::Select; 112: use IO::File; 113: use Socket; 114: use Fcntl; 115: use Tie::RefHash; 116: 117: use File::Find; 118: use localenroll; 119: 120: ######################################################## 121: ######################################################## 122: 123: =pod 124: 125: =item Variables required for forking 126: 127: =over 4 128: 129: =item $MAX_CLIENTS_PER_CHILD 130: 131: The number of clients each child should process. 132: 133: =item %children 134: 135: The keys to %children are the current child process IDs 136: 137: =item $children 138: 139: The current number of children 140: 141: =back 142: 143: =cut 144: 145: ######################################################## 146: ######################################################## 147: my $MAX_CLIENTS_PER_CHILD = 5; # number of clients each child should process 148: my %children = (); # keys are current child process IDs 149: my $children = 0; # current number of children 150: 151: ################################################################### 152: ################################################################### 153: 154: =pod 155: 156: =item Main body of code. 157: 158: =over 4 159: 160: =item Read data from loncapa_apache.conf and loncapa.conf. 161: 162: =item Ensure we can access the database. 163: 164: =item Determine if there are other instances of lonsql running. 165: 166: =item Read the hosts file. 167: 168: =item Create a socket for lonsql. 169: 170: =item Fork once and dissociate from parent. 171: 172: =item Write PID to disk. 173: 174: =item Prefork children and maintain the population of children. 175: 176: =back 177: 178: =cut 179: 180: ################################################################### 181: ################################################################### 182: my $childmaxattempts=10; 183: my $run =0; # running counter to generate the query-id 184: # 185: # Read loncapa_apache.conf and loncapa.conf 186: # 187: my $perlvarref=LONCAPA::Configuration::read_conf('loncapa.conf'); 188: my %perlvar=%{$perlvarref}; 189: # 190: # Write the /home/www/.my.cnf file 191: my $conf_file = '/home/www/.my.cnf'; 192: if (! -e $conf_file) { 193: if (open MYCNF, ">$conf_file") { 194: print MYCNF <<"ENDMYCNF"; 195: [client] 196: user=www 197: password=$perlvar{'lonSqlAccess'} 198: ENDMYCNF 199: close MYCNF; 200: } else { 201: warn "Unable to write $conf_file, continuing"; 202: } 203: } 204: 205: 206: # 207: # Check if other instance running 208: # 209: my $pidfile="$perlvar{'lonDaemons'}/logs/lonsql.pid"; 210: if (-e $pidfile) { 211: my $lfh=IO::File->new("$pidfile"); 212: my $pide=<$lfh>; 213: chomp($pide); 214: if (kill 0 => $pide) { die "already running"; } 215: } 216: 217: # 218: # Read hosts file 219: # 220: my $thisserver; 221: my $PREFORK=4; # number of children to maintain, at least four spare 222: open (CONFIG,"$perlvar{'lonTabDir'}/hosts.tab") || die "Can't read host file"; 223: while (my $configline=<CONFIG>) { 224: my ($id,$domain,$role,$name)=split(/:/,$configline); 225: $name=~s/\s//g; 226: $thisserver=$name if ($id eq $perlvar{'lonHostID'}); 227: #$PREFORK++; 228: } 229: close(CONFIG); 230: # 231: #$PREFORK=int($PREFORK/4); 232: 233: # 234: # Create a socket to talk to lond 235: # 236: my $unixsock = "mysqlsock"; 237: my $localfile="$perlvar{'lonSockDir'}/$unixsock"; 238: my $server; 239: unlink ($localfile); 240: unless ($server=IO::Socket::UNIX->new(Local =>"$localfile", 241: Type => SOCK_STREAM, 242: Listen => 10)) { 243: print "in socket error:$@\n"; 244: } 245: 246: # 247: # Fork once and dissociate 248: # 249: my $fpid=fork; 250: exit if $fpid; 251: die "Couldn't fork: $!" unless defined ($fpid); 252: POSIX::setsid() or die "Can't start new session: $!"; 253: 254: # 255: # Write our PID on disk 256: my $execdir=$perlvar{'lonDaemons'}; 257: open (PIDSAVE,">$execdir/logs/lonsql.pid"); 258: print PIDSAVE "$$\n"; 259: close(PIDSAVE); 260: &logthis("CRITICAL: ---------- Starting ----------"); 261: 262: # 263: # Ignore signals generated during initial startup 264: $SIG{HUP}=$SIG{USR1}='IGNORE'; 265: # Now we are on our own 266: # Fork off our children. 267: for (1 .. $PREFORK) { 268: make_new_child(); 269: } 270: 271: # 272: # Install signal handlers. 273: $SIG{CHLD} = \&REAPER; 274: $SIG{INT} = $SIG{TERM} = \&HUNTSMAN; 275: $SIG{HUP} = \&HUPSMAN; 276: 277: # 278: # And maintain the population. 279: while (1) { 280: sleep; # wait for a signal (i.e., child's death) 281: for (my $i = $children; $i < $PREFORK; $i++) { 282: make_new_child(); # top up the child pool 283: } 284: } 285: 286: ######################################################## 287: ######################################################## 288: 289: =pod 290: 291: =item &make_new_child 292: 293: Inputs: None 294: 295: Returns: None 296: 297: =cut 298: 299: ######################################################## 300: ######################################################## 301: sub make_new_child { 302: my $pid; 303: my $sigset; 304: # 305: # block signal for fork 306: $sigset = POSIX::SigSet->new(SIGINT); 307: sigprocmask(SIG_BLOCK, $sigset) 308: or die "Can't block SIGINT for fork: $!\n"; 309: # 310: die "fork: $!" unless defined ($pid = fork); 311: # 312: if ($pid) { 313: # Parent records the child's birth and returns. 314: sigprocmask(SIG_UNBLOCK, $sigset) 315: or die "Can't unblock SIGINT for fork: $!\n"; 316: $children{$pid} = 1; 317: $children++; 318: return; 319: } else { 320: # Child can *not* return from this subroutine. 321: $SIG{INT} = 'DEFAULT'; # make SIGINT kill us as it did before 322: # unblock signals 323: sigprocmask(SIG_UNBLOCK, $sigset) 324: or die "Can't unblock SIGINT for fork: $!\n"; 325: 326: $SIG{TERM}=$SIG{INT}=$SIG{QUIT}=$SIG{__DIE__}=\&DISCONNECT; 327: # handle connections until we've reached $MAX_CLIENTS_PER_CHILD 328: for (my $i=0; $i < $MAX_CLIENTS_PER_CHILD; $i++) { 329: my $client = $server->accept() or last; 330: # do something with the connection 331: $run = $run+1; 332: my $userinput = <$client>; 333: chomp($userinput); 334: # 335: my ($conserver,$query, 336: $arg1,$arg2,$arg3)=split(/&/,$userinput); 337: my $query=unescape($query); 338: # 339: #send query id which is pid_unixdatetime_runningcounter 340: my $queryid = $thisserver; 341: $queryid .="_".($$)."_"; 342: $queryid .= time."_"; 343: $queryid .= $run; 344: print $client "$queryid\n"; 345: # 346: # &logthis("QUERY: $query - $arg1 - $arg2 - $arg3"); 347: sleep 1; 348: # 349: my $result=''; 350: # 351: # At this point, query is received, query-ID assigned and sent 352: # back, $query eq 'logquery' will mean that this is a query 353: # against log-files 354: if (($query eq 'userlog') || ($query eq 'courselog')) { 355: # beginning of log query 356: my $udom = &unescape($arg1); 357: my $uname = &unescape($arg2); 358: my $command = &unescape($arg3); 359: my $path = &propath($udom,$uname); 360: if (-e "$path/activity.log") { 361: if ($query eq 'userlog') { 362: $result=&userlog($path,$command); 363: } else { 364: $result=&courselog($path,$command); 365: } 366: } else { 367: &logthis('Unable to do log query: '.$uname.'@'.$udom); 368: $result='no_such_file'; 369: } 370: # end of log query 371: } elsif ($query eq 'fetchenrollment') { 372: # retrieve institutional class lists 373: my $dom = &unescape($arg1); 374: my %affiliates = (); 375: my %replies = (); 376: my $locresult = ''; 377: my $querystr = &unescape($arg3); 378: foreach (split/%%/,$querystr) { 379: if (/^([^=]+)=([^=]+)$/) { 380: @{$affiliates{$1}} = split/,/,$2; 381: } 382: } 383: $locresult = &localenroll::fetch_enrollment($dom,\%affiliates,\%replies); 384: $result = &escape($locresult.':'); 385: if ($locresult) { 386: $result .= &escape(join(':',map{$_.'='.$replies{$_}} keys %replies)); 387: } 388: } elsif ($query eq 'prepare activity log') { 389: my ($cid,$domain) = map {&unescape($_);} ($arg1,$arg2); 390: &logthis('preparing activity log tables for '.$cid); 391: my $command = 392: qq{$perlvar{'lonDaemons'}/parse_activity_log.pl -course=$cid -domain=$domain}; 393: system($command); 394: &logthis($command); 395: my $returnvalue = $?>>8; 396: if ($returnvalue) { 397: $result = 'error: parse_activity_log.pl returned '. 398: $returnvalue; 399: } else { 400: $result = 'success'; 401: } 402: } else { 403: # Do an sql query 404: $result = &do_sql_query($query,$arg1,$arg2); 405: } 406: # result does not need to be escaped because it has already been 407: # escaped. 408: #$result=&escape($result); 409: &reply("queryreply:$queryid:$result",$conserver); 410: } 411: # tidy up gracefully and finish 412: # 413: 414: # this exit is VERY important, otherwise the child will become 415: # a producer of more and more children, forking yourself into 416: # process death. 417: exit; 418: } 419: } 420: 421: ######################################################## 422: ######################################################## 423: 424: =pod 425: 426: =item &do_sql_query 427: 428: Runs an sql metadata table query. 429: 430: Inputs: $query, $custom, $customshow 431: 432: Returns: A string containing escaped results. 433: 434: =cut 435: 436: ######################################################## 437: ######################################################## 438: { 439: my @metalist; 440: 441: sub process_file { 442: if ( -e $_ && # file exists 443: -f $_ && # and is a normal file 444: /\.meta$/ && # ends in meta 445: ! /^.+\.\d+\.[^\.]+\.meta$/ # is not a previous version 446: ) { 447: push(@metalist,$File::Find::name); 448: } 449: } 450: 451: sub do_sql_query { 452: my ($query) = @_; 453: &logthis('doing query '.$query); 454: 455: my @results = (); 456: 457: # 458: if ($query) { 459: #prepare and execute the query 460: my $aref=&nsdl_query($query); 461: foreach my $row (@$aref) { 462: my @b=map { &escape($_); } @$row; 463: push @results,join(",", @b); 464: } 465: 466: } 467: return join("&",@results); 468: } # End of &do_sql_query 469: 470: } # End of scoping curly braces for &process_file and &do_sql_query 471: ######################################################## 472: ######################################################## 473: 474: =pod 475: 476: =item &logthis 477: 478: Inputs: $message, the message to log 479: 480: Returns: nothing 481: 482: Writes $message to the logfile. 483: 484: =cut 485: 486: ######################################################## 487: ######################################################## 488: sub logthis { 489: my $message=shift; 490: my $execdir=$perlvar{'lonDaemons'}; 491: my $fh=IO::File->new(">>$execdir/logs/lonsql.log"); 492: my $now=time; 493: my $local=localtime($now); 494: print $fh "$local ($$): $message\n"; 495: } 496: 497: # -------------------------------------------------- Non-critical communication 498: 499: ######################################################## 500: ######################################################## 501: 502: =pod 503: 504: =item &subreply 505: 506: Sends a command to a server. Called only by &reply. 507: 508: Inputs: $cmd,$server 509: 510: Returns: The results of the message or 'con_lost' on error. 511: 512: =cut 513: 514: ######################################################## 515: ######################################################## 516: sub subreply { 517: my ($cmd,$server)=@_; 518: my $peerfile="$perlvar{'lonSockDir'}/$server"; 519: my $sclient=IO::Socket::UNIX->new(Peer =>"$peerfile", 520: Type => SOCK_STREAM, 521: Timeout => 10) 522: or return "con_lost"; 523: print $sclient "$cmd\n"; 524: my $answer=<$sclient>; 525: chomp($answer); 526: $answer="con_lost" if (!$answer); 527: return $answer; 528: } 529: 530: ######################################################## 531: ######################################################## 532: 533: =pod 534: 535: =item &reply 536: 537: Sends a command to a server. 538: 539: Inputs: $cmd,$server 540: 541: Returns: The results of the message or 'con_lost' on error. 542: 543: =cut 544: 545: ######################################################## 546: ######################################################## 547: sub reply { 548: my ($cmd,$server)=@_; 549: my $answer; 550: if ($server ne $perlvar{'lonHostID'}) { 551: $answer=subreply($cmd,$server); 552: if ($answer eq 'con_lost') { 553: $answer=subreply("ping",$server); 554: $answer=subreply($cmd,$server); 555: } 556: } else { 557: $answer='self_reply'; 558: $answer=subreply($cmd,$server); 559: } 560: return $answer; 561: } 562: 563: ######################################################## 564: ######################################################## 565: 566: =pod 567: 568: =item &escape 569: 570: Escape special characters in a string. 571: 572: Inputs: string to escape 573: 574: Returns: The input string with special characters escaped. 575: 576: =cut 577: 578: ######################################################## 579: ######################################################## 580: sub escape { 581: my $str=shift; 582: $str =~ s/(\W)/"%".unpack('H2',$1)/eg; 583: return $str; 584: } 585: 586: ######################################################## 587: ######################################################## 588: 589: =pod 590: 591: =item &unescape 592: 593: Unescape special characters in a string. 594: 595: Inputs: string to unescape 596: 597: Returns: The input string with special characters unescaped. 598: 599: =cut 600: 601: ######################################################## 602: ######################################################## 603: sub unescape { 604: my $str=shift; 605: $str =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C",hex($1))/eg; 606: return $str; 607: } 608: 609: ######################################################## 610: ######################################################## 611: 612: =pod 613: 614: =item &ishome 615: 616: Determine if the current machine is the home server for a user. 617: The determination is made by checking the filesystem for the users information. 618: 619: Inputs: $author 620: 621: Returns: 0 - this is not the authors home server, 1 - this is. 622: 623: =cut 624: 625: ######################################################## 626: ######################################################## 627: sub ishome { 628: my $author=shift; 629: $author=~s/\/home\/httpd\/html\/res\/([^\/]*)\/([^\/]*).*/$1\/$2/; 630: my ($udom,$uname)=split(/\//,$author); 631: my $proname=propath($udom,$uname); 632: if (-e $proname) { 633: return 1; 634: } else { 635: return 0; 636: } 637: } 638: 639: ######################################################## 640: ######################################################## 641: 642: =pod 643: 644: =item &propath 645: 646: Inputs: user name, user domain 647: 648: Returns: The full path to the users directory. 649: 650: =cut 651: 652: ######################################################## 653: ######################################################## 654: sub propath { 655: my ($udom,$uname)=@_; 656: $udom=~s/\W//g; 657: $uname=~s/\W//g; 658: my $subdir=$uname.'__'; 659: $subdir =~ s/(.)(.)(.).*/$1\/$2\/$3/; 660: my $proname="$perlvar{'lonUsersDir'}/$udom/$subdir/$uname"; 661: return $proname; 662: } 663: 664: ######################################################## 665: ######################################################## 666: 667: =pod 668: 669: =item &courselog 670: 671: Inputs: $path, $command 672: 673: Returns: unescaped string of values. 674: 675: =cut 676: 677: ######################################################## 678: ######################################################## 679: sub courselog { 680: my ($path,$command)=@_; 681: my %filters=(); 682: foreach (split(/\:/,&unescape($command))) { 683: my ($name,$value)=split(/\=/,$_); 684: $filters{$name}=$value; 685: } 686: my @results=(); 687: open(IN,$path.'/activity.log') or return ('file_error'); 688: while (my $line=<IN>) { 689: chomp($line); 690: my ($timestamp,$host,$log)=split(/\:/,$line); 691: # 692: # $log has the actual log entries; currently still escaped, and 693: # %26(timestamp)%3a(url)%3a(user)%3a(domain) 694: # then additionally 695: # %3aPOST%3a(name)%3d(value)%3a(name)%3d(value) 696: # or 697: # %3aCSTORE%3a(name)%3d(value)%26(name)%3d(value) 698: # 699: # get delimiter between timestamped entries to be &&& 700: $log=~s/\%26(\d+)\%3a/\&\&\&$1\%3a/g; 701: # now go over all log entries 702: foreach (split(/\&\&\&/,&unescape($log))) { 703: my ($time,$res,$uname,$udom,$action,@values)=split(/\:/,$_); 704: my $values=&unescape(join(':',@values)); 705: $values=~s/\&/\:/g; 706: $res=&unescape($res); 707: my $include=1; 708: if (($filters{'username'}) && ($uname ne $filters{'username'})) 709: { $include=0; } 710: if (($filters{'domain'}) && ($udom ne $filters{'domain'})) 711: { $include=0; } 712: if (($filters{'url'}) && ($res!~/$filters{'url'}/)) 713: { $include=0; } 714: if (($filters{'start'}) && ($time<$filters{'start'})) 715: { $include=0; } 716: if (($filters{'end'}) && ($time>$filters{'end'})) 717: { $include=0; } 718: if (($filters{'action'} eq 'view') && ($action)) 719: { $include=0; } 720: if (($filters{'action'} eq 'submit') && ($action ne 'POST')) 721: { $include=0; } 722: if (($filters{'action'} eq 'grade') && ($action ne 'CSTORE')) 723: { $include=0; } 724: if ($include) { 725: push(@results,($time<1000000000?'0':'').$time.':'.$res.':'. 726: $uname.':'.$udom.':'. 727: $action.':'.$values); 728: } 729: } 730: } 731: close IN; 732: return join('&',sort(@results)); 733: } 734: 735: ######################################################## 736: ######################################################## 737: 738: =pod 739: 740: =item &userlog 741: 742: Inputs: $path, $command 743: 744: Returns: unescaped string of values. 745: 746: =cut 747: 748: ######################################################## 749: ######################################################## 750: sub userlog { 751: my ($path,$command)=@_; 752: my %filters=(); 753: foreach (split(/\:/,&unescape($command))) { 754: my ($name,$value)=split(/\=/,$_); 755: $filters{$name}=$value; 756: } 757: my @results=(); 758: open(IN,$path.'/activity.log') or return ('file_error'); 759: while (my $line=<IN>) { 760: chomp($line); 761: my ($timestamp,$host,$log)=split(/\:/,$line); 762: $log=&unescape($log); 763: my $include=1; 764: if (($filters{'start'}) && ($timestamp<$filters{'start'})) 765: { $include=0; } 766: if (($filters{'end'}) && ($timestamp>$filters{'end'})) 767: { $include=0; } 768: if (($filters{'action'} eq 'log') && ($log!~/^Log/)) { $include=0; } 769: if (($filters{'action'} eq 'check') && ($log!~/^Check/)) 770: { $include=0; } 771: if ($include) { 772: push(@results,$timestamp.':'.$log); 773: } 774: } 775: close IN; 776: return join('&',sort(@results)); 777: } 778: 779: ######################################################## 780: ######################################################## 781: 782: =pod 783: 784: =item Functions required for forking 785: 786: =over 4 787: 788: =item REAPER 789: 790: REAPER takes care of dead children. 791: 792: =item HUNTSMAN 793: 794: Signal handler for SIGINT. 795: 796: =item HUPSMAN 797: 798: Signal handler for SIGHUP 799: 800: =item DISCONNECT 801: 802: Disconnects from database. 803: 804: =back 805: 806: =cut 807: 808: ######################################################## 809: ######################################################## 810: sub REAPER { # takes care of dead children 811: $SIG{CHLD} = \&REAPER; 812: my $pid = wait; 813: $children --; 814: &logthis("Child $pid died"); 815: delete $children{$pid}; 816: } 817: 818: sub HUNTSMAN { # signal handler for SIGINT 819: local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children 820: kill 'INT' => keys %children; 821: my $execdir=$perlvar{'lonDaemons'}; 822: unlink("$execdir/logs/lonsql.pid"); 823: &logthis("CRITICAL: Shutting down"); 824: $unixsock = "mysqlsock"; 825: my $port="$perlvar{'lonSockDir'}/$unixsock"; 826: unlink($port); 827: exit; # clean up with dignity 828: } 829: 830: sub HUPSMAN { # signal handler for SIGHUP 831: local($SIG{CHLD}) = 'IGNORE'; # we're going to kill our children 832: kill 'INT' => keys %children; 833: close($server); # free up socket 834: &logthis("CRITICAL: Restarting"); 835: my $execdir=$perlvar{'lonDaemons'}; 836: $unixsock = "mysqlsock"; 837: my $port="$perlvar{'lonSockDir'}/$unixsock"; 838: unlink($port); 839: exec("$execdir/lonsql"); # here we go again 840: } 841: 842: # 843: # Takes SQL query 844: # sends it to NSDL 845: # has to return array reference 846: # 847: 848: sub nsdl_query { 849: my $query=shift; 850: } 851: 852: =pod 853: 854: =back 855: 856: =cut