[Koha] Slow Koha OPAC login process

[Mark Alexander]

Excerpts from Michael Kuhn's message of 2017-05-09 19:57:51 +0200:
> With my poor Perl knowledge I have now measured the execution time of 
> the various parts of script "opac-user.pl". As I found out everything is 
> always very fast (using less than 1 second execution time) except the 
> very last function in this script which looks as follows:
> 
> output_with_http_headers $cgi, $cookie, $template->output, $content_type;

I am not familiar with this code, but I took a quick look at it just
now.  If I were trying to debug this problem, I would measure the
execution time of the last statement in output_with_http_headers:

    print $query->header($options), $data;

If I understand correctly, this print is going to send a big blob of
HTML (preceded by a header) via Apache to the client.  If Apache is
timing out for some reason, perhaps that would cause a big delay in
this print statement.