sendmails works, but opens 43 file handles per email -> problem Post: 302480911

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Top Forums UNIX for Advanced & Expert Users sendmails works, but opens 43 file handles per email -> problem Post 302480911 by ZX81 on Thursday 16th of December 2010 06:12:34 AM

12-16-2010

Registered User

sendmails works, but opens 43 file handles per email -> problem

I'm using Sendmail 8.13.8 on a CentOS 5.5 vServer (Virtuozzo).

I'm using a loop in PHP to send a lot of HTML-mails via sendmail. Each mail is a mail with individual statistics for our users, so its not mass mailing, bcc is not an option.

It all works fine, but when I take a closer look there is a problem heading our way with a high number of mails:

For each mail sendmail opens up 43 files. Sometimes these open files get closed again very fast, sometimes not.

Here is an example using the PHP-script below, it sends 20 mails in a loop:

[root]# php test-mail.php
START: number of open files: 2113
END: number of open files: 2973

This is the worst case. The number of open files (lsof | wc -l) used to send the 20 mails is 860 => 43 open files per mail.

Sometimes the files are closed very fast, so I get results like this, too:

[root]# php test-mail.php
START: number of open files: 2113
END: number of open files: 2242

This shows 129 (3 * 43) open files, so the open files for 17 send mails are already closed, for 3 mails the 129 files are still open.

In the worst case and with lots of mails our server crashes, the numfile limit of 8192 in user_beancounters is reached (our ISP won't give us more than 8192).

Sendmail DeliveryMode is background.

Could it be that sendmail tries to send lots ob mails asyncronously and uses 43 open files for each? I'm only depending on sendmail to deliver the mails, normaly I wouldn't dare to touch the sendmail config (like 'if you don't know what you're doing, don't!').

Any ideas?

BTW: It is not a problem of PHP. I verified this by sending mails via SMTP localhost to sendmail (opened 43 files per mail) and sending mails via SMTP to an ISP-relay (did not open any files per mail).

Thank you very much for reading this,
best,
Andreas

This is the code for test-mail.php:

Code:

<?php
$output = shell_exec('lsof | wc -l');
echo "START: number of open files: $output";

// HTML message
$msg = '<html><head><title>Test mail</title></head><body><p>Mailbody</p></body></html>';

// Set 'Content-type'-header
$header  = 'MIME-Version: 1.0' . "\r\n";
$header .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";

for($i=0; $i<20; $i++) {
	// send mail, this opens up 43 files for each
	mail('you@yourdomain.com', 'Testmail '.$i, $msg, $header, '-f bounce@yourdomain.com');
}

$output = shell_exec('lsof | wc -l');
echo "END: number of open files: $output";
?>

ZX81

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LEARN ABOUT DEBIAN

sendmailconfig

SENDMAILCONFIG(8)					      System Manager's Manual						 SENDMAILCONFIG(8)

NAME

       sendmailconfig - configure sendmail for Debian systems

SYNOPSIS

       sendmailconfig [--no-reload]

DESCRIPTION

       sendmailconfig is used to simplify the configuration of sendmail(8) for use on Debian systems.

       In  the	simplest  case,  you  may  run	this program to (re)configure sendmail for your Debian system at any time. It will modify the file
       /etc/mail/sendmail.mc in order to create a working sendmail configuration which will be written to the file /etc/mail/sendmail.cf.

       For advanced configurations, you can modify the sendmail.mc file before generating sendmail.cf. Future invokations of  sendmailconfig  will
       preserve these changes provided they are made at the end of the file.

       Normally  sendmailconfig  will  ask  if	you want to reload sendmail after making changes to its configuration. The --no-reload option will
       avoid this question.

FILES

       /etc/mail/sendmail.mc
	      sendmail m4 input to generate sendmail.cf

       /etc/mail/sendmail.cf
	      actual sendmail configuration file

       /etc/mail/sendmail.cw
	      names for which we will accept mail in the standard configuration

       /etc/mail/sendmail.ct
	      names of trusted users in the standard configuration

SEE ALSO

       sendmail(8)

AUTHOR

       Robert Leslie <rob@mars.org>

								    21-Jan-1997 						 SENDMAILCONFIG(8)