Foswiki plugin on Perl/FCGI failed to use File:Find at the 5th attempt - perl

Question

I am writing a REST plugin for Foswiki using Perl and I am facing an reliability issue when using File::Find. I have tried my best to write a minimal reproducible example. The plugin uses File::Find to traverse directories and print the filenames in the HTTP response. The REST request is working properly 4 times, but stop to work the 5th time. The HTTP status remain “HTTP/1.1 200 OK” but no file is reported by File::Find anymore.
The webserver is nginx and is configured to use FastCGI. It appear to run 4 working threads managed by foswiki-fcgi-pm:
> ps aux
www-data 16957 0.0 7.7 83412 78332 ? Ss 16:52 0:00 foswiki-fcgi-pm
www-data 16960 0.0 7.5 83960 76740 ? S 16:52 0:00 foswiki-fcgi
www-data 16961 0.0 7.6 84004 76828 ? S 16:52 0:00 foswiki-fcgi
www-data 16962 0.0 7.6 83956 76844 ? S 16:52 0:00 foswiki-fcgi
www-data 16963 0.0 7.5 83960 76740 ? S 16:52 0:00 foswiki-fcgi
Firstly, the plugin initialization simply register the REST handler:
sub initPlugin {
my ( $topic, $web, $user, $installWeb ) = #_;
# check for Plugins.pm versions
if ( $Foswiki::Plugins::VERSION < 2.3 ) {
Foswiki::Func::writeWarning( 'Version mismatch between ',
__PACKAGE__, ' and Plugins.pm' );
return 0;
}
Foswiki::Func::registerRESTHandler(
'restbug', \&RestBug,
authenticate => 0, # Set to 0 if handler should be useable by WikiGuest
validate => 0, # Set to 0 to disable StrikeOne CSRF protection
http_allow => 'GET,POST', # Set to 'GET,POST' to allow use HTTP GET and POST
description => 'Debug'
);
# Plugin correctly initialized
return 1;
}
Secondly, the REST handler is implemented as follow, printing all the files it can possibly find:
sub RestBug {
my ($session, $subject, $verb, $response) = #_;
my #Directories = ("/var/www/foswiki/tools");
sub findfilestest
{
$response->print("FILE $_\n");
}
find({ wanted => \&findfilestest }, #Directories );
}
When I test the REST service with a HTTP request, the first 4 times I get the following HTTP response, which seems quite satisfying:
HTTP/1.1 200 OK
Server: nginx/1.14.2
Date: Tue, 22 Nov 2022 09:23:10 GMT
Content-Length: 541
Connection: keep-alive
Set-Cookie: SFOSWIKISID=385db599c5d66bb19591e1eef7f1a854; path=/; secure; HttpOnly
FILE .
FILE foswiki.freebsd.init-script
FILE bulk_copy.pl
FILE dependencies
FILE mod_perl_startup.pl
FILE geturl.pl
FILE extender.pl
FILE extension_installer
FILE configure
FILE lighttpd.pl
FILE foswiki.freebsd.etc-defaults
FILE save-pending-checkins
FILE babelify
FILE upgrade_emails.pl
FILE tick_foswiki.pl
FILE foswiki.defaults
FILE rewriteshebang.pl
FILE fix_file_permissions.sh
FILE foswiki.init-script
FILE convertTopicSettings.pl
FILE mailnotify
FILE html2tml.pl
FILE tml2html.pl
FILE systemd
FILE foswiki.service
The following attempts give this unexpected response:
HTTP/1.1 200 OK
Server: nginx/1.14.2
Date: Tue, 22 Nov 2022 09:24:56 GMT
Transfer-Encoding: chunked
Connection: keep-alive
Set-Cookie: SFOSWIKISID=724b2c4b1ddfbebd25d0dc2a0f182142; path=/; secure; HttpOnly
Note that if I restart Foswiki with the command systemctl restart foswiki, the REST service work again 4 more times.
How to make this REST service work more than 4 times in a row?