Vigilando a los Vigilantes

Es posible monitorizar el estado de los vigilantes usando el módulo NetServer::Portal. Para instrumentar la aplicación es necesario añadirle unas líneas de código que arrancan un servidor que monitoriza a los vigilantes. Es posible entonces obtener información de ese servidor conectándose a un determinado puerto. La información se presenta en un formato similar a la de la tradicional utilidad Unix top :

% !top

-----------------------------------------------------
watchthewatchers.pl PID=6901 @ nereida.deioc.ull.es          | 10:45:41 [  60s]
7 events; load averages: 0.00, 0.00, 0.00; lag  0%

  EID PRI STATE   RAN  TIME   CPU TYPE DESCRIPTION                           P1
    0   7          10  0:07100.0%  sys idle
    2   3 cpu       1  0:00  0.0%   io NetServer::Portal::Client localhost
    5   4 sleep     4  0:00  0.0% time ?? watchthewatchers.pl:20
    4   4 sleep     8  0:00  0.0%  var ?? watchthewatchers.pl:26
    3   4 sleep     4  0:00  0.0%  var ?? watchthewatchers.pl:32
    1   3 sleep     2  0:00  0.0% time Event::Stats
    6   3 sleep     0  0:00  0.0%   io NetServer::Portal
    7   5 wait      0  0:00  0.0% idle NetServer::Portal /var/tmp/watchthewatch
    0  -1           0  0:00  0.0%  sys other processes

Los pasos para monitorizar un programa Event son:

• Añada a su programa las líneas

  'NetServer::Portal'->default_start();  # creates server
  warn "NetServer::Portal listening on port ".(7000+($$ % 1000))."\n";
  

• Ejecutamos el programa

  pp2@nereida:~/src/perl/Event$ watchthewatchers.pl
  can't open /var/tmp/watchthewatcherspl.npc: No existe el fichero o el directorio at /usr/local/share/perl/5.8.8/NetServer/Portal.pm line 73
  NetServer::Portal listening on port 7901
  1209462175.88446: Modified variable
  1209462175.88465: Write detected. new value: 1
  1209462175.88478: Read detected
  1209462177.88442: Modified variable
  1209462177.88451: Read detected
  1209462177.88453: Write detected. new value: 2
  1209462177.88456: Read detected
  1209462179.88436: Modified variable
  .................................
  

• Nos conectamos via telnet al puerto indicado

  pp2@nereida:~/src/perl/Event$ telnet localhost 7901
  Trying 127.0.0.1...
  Connected to localhost.
  Escape character is '^]'.
  [nereida.deioc.ull.es] ./watchthewatchers.pl #6901
  
  login: pp2
  
  -----------------------------------------------------
  NetServer::Portal v1.08
  
  HOST: nereida.deioc.ull.es
  PID:  6901
  USER: pp2
  
  
    !about     About This Extension
    !menu      Main Menu
    !pi        Perl Introspector
    !top       Process Top
    !exit      End Session
  
    dim r,c    Change screen dimensions from [24,80]
  

• Escribimos !top

  % !top
  
  -----------------------------------------------------
  watchthewatchers.pl PID=6901 @ nereida.deioc.ull.es          | 10:45:41 [  60s]
  7 events; load averages: 0.00, 0.00, 0.00; lag  0%
  
    EID PRI STATE   RAN  TIME   CPU TYPE DESCRIPTION                           P1
      0   7          10  0:07100.0%  sys idle
      2   3 cpu       1  0:00  0.0%   io NetServer::Portal::Client localhost
      5   4 sleep     4  0:00  0.0% time ?? watchthewatchers.pl:20
      4   4 sleep     8  0:00  0.0%  var ?? watchthewatchers.pl:26
      3   4 sleep     4  0:00  0.0%  var ?? watchthewatchers.pl:32
      1   3 sleep     2  0:00  0.0% time Event::Stats
      6   3 sleep     0  0:00  0.0%   io NetServer::Portal
      7   5 wait      0  0:00  0.0% idle NetServer::Portal /var/tmp/watchthewatch
      0  -1           0  0:00  0.0%  sys other processes
  

• Para obtener ayuda tecleamos ?
• La finalización del programa termina también la sesión telnet

Sigue el programa monitorizado en este ejemplo:

pp2@nereida:~/src/perl/Event$ cat -n watchthewatchers.pl
 1  #!/usr/bin/perl
 2  use warnings;
 3  use strict;
 4
 5  use Event qw{time};
 6  require NetServer::Portal;
 7
 8  'NetServer::Portal'->default_start();  # creates server
 9  warn "NetServer::Portal listening on port ".(7000+($$ % 1000))."\n";
10
11  my $var = 0;
12
13  Event->timer(
14    interval => 2,
15    cb => sub {
16      $var++;
17      warn time.": Modified variable\n";
18      return;
19    }
20  );
21
22  Event->var(
23    var => \$var,
24    poll => 'r',
25    cb => sub { print time.": Read detected\n"; },
26  );
27
28  Event->var(
29    var => \$var,
30    poll => 'w',
31    cb => sub { print time.": Write detected. new value: $var\n" },
32  );
33
34  Event::loop;