Download of large files from slow connection stops

Hello,

we just moved to a new server using Debian6 and basically following "The Perfect Server" Howto. Everything is running smooth, except for one problem:

when a client with small bandwidth tries to download a large zip file (120MB) from a login area of our main website, the download stops after a a few minutes and the result is a broken zip file with 6 to 40 MB - depending on the speed of their connection.

I have yet to check logs, but Google tells me that this might be a problem with TCP/IP disconnecting after 5 Minutes of inactivity.

I was able to reproduce the error from a slow connection. Will have to do further testing, but if someone here has encountered this before, please point me in the right direction...

The script itself is about 1 yr old has not caused this behavior on the old webserver.


- Richard

 

Which browser did you use? Does the same behaviour occur if you use another browser?

 

So far I tested only on FF4 on a MAC.

I did look at Apache logs, these show the file being called and a status 200, but nothing in Error Logs.
Since I have only approximate times from a salesperson that talked to the persons downloading the file, I have only found one entry that is fairly certain one that failed (since there are no other downloads for hours):

 

I didn't write the script - it is a Download manager for Joomla that we modified quite a bit, but it seems it is using fopen().

Here comes the script, at least part of it:

PHP:

    function download($inline = false)
    {
        // Fix [3164]
        while (@ob_end_clean());

        if( $this->_isLink ){
            header( "Location: " . substr( $this->name , 6 ) );
            return;
        }

        $fsize = @filesize($this->path.$this->name);
        $mod_date = date('r', filemtime( $this->path.$this->name ) );
        $cont_dis = $inline ? 'inline' : 'attachment';

        // required for IE, otherwise Content-disposition is ignored
        if(ini_get('zlib.output_compression'))  {
            ini_set('zlib.output_compression', 'Off');
        }

        // fix for IE7/8, ticket #183
        if(function_exists('apache_setenv')) {
            apache_setenv('no-gzip', '1');
        }

        header("Pragma: public");
        header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
        header("Expires: 0");
        header("Content-Transfer-Encoding: binary");
        header('Content-Disposition:' . $cont_dis .';'
            . ' filename="' . str_replace('"', '\"', $this->name) . '";'
            . ' modification-date="' . $mod_date . '";'
            . ' size=' . $fsize .';'
            ); //RFC2183
        header("Content-Type: "    . $this->mime );            // MIME type
        header("Content-Length: "  . $fsize);

        if( ! ini_get('safe_mode') ) { // set_time_limit doesn't work in safe mode
            @set_time_limit(0);
        }

         // No encoding - we aren't using compression... (RFC1945)
        //header("Content-Encoding: none");
        //header("Vary: none");


        $this->readfile_chunked($this->path.$this->name);
        // The caller MUST 'die();'
    }

    function readfile_chunked($filename,$retbytes=true)
    {
           $chunksize = 1*(1024*1024); // how many bytes per chunk
           $buffer = '';
           $cnt =0;
           $handle = fopen($filename, 'rb');
           if ($handle === false) {
               return false;
           }
           while (!feof($handle)) {
               $buffer = fread($handle, $chunksize);
               echo $buffer;
            @ob_flush();
            flush();
               if ($retbytes) {
                   $cnt += strlen($buffer);
               }
           }
       $status = fclose($handle);
          if ($retbytes && $status) {
               return $cnt; // return num. bytes delivered like readfile() does.
           }
           return $status;
    }

     function exists() {
        if( $this->_isLink ){
            return true;
        }
        return file_exists($this->path.DS.$this->name);
    }

    function isLink(){
        return $this->_isLink ;
    }

    /**
    *    Get file size
    *
    *    @desc Gets the file size and convert it to friendly format
    *    @param void
    *    @return string Returns filesize in a friendly format.
    */

    function getSize()
    {
        if( $this->_isLink ){
            return 'Link';
        }
        $kb = 1024;
        $mb = 1024 * $kb;
        $gb = 1024 * $mb;
        $tb = 1024 * $gb;

        $size = $this->size;

        if ($size) {
            if ($size < $kb) {
                $file_size = $size .' '. _DML_BYTES;
            }
            elseif ($size < $mb) {
                $final = round($size/$kb,2);
                $file_size = $final .' '. _DML_KB;
            }
            elseif ($size < $gb) {
                $final = round($size/$mb,2);
                $file_size = $final .' '. _DML_MB;
            }
            elseif($size < $tb) {
                $final = round($size/$gb,2);
                $file_size = $final .' '. _DML_GB;
            } else {
                $final = round($size/$tb,2);
                $file_size = $final .' '. _DML_TB;
            }
        } else {
           if( $size == 0 ) {
               $file_size = _DML_EMPTY;
           } else {
                $file_size = _DML_ERROR;
           }
        }
        return $file_size;
    }



 

sorry, I was out...

We use Fast-CGI with SuEXEC.

There are a few errors (apache2), but I did not think them relevant:

Nothing in the client error log.

 

You can try and set a higher timeout: http://www.php.net/manual/en/function.stream-set-timeout.php

 

thanks, yes I'll try that.
But as I stated, this problem did not exist on the "old" server - it was not on fast-cgi - so I suspect that it has to do with some sort of server timing on fast-cgi.