How to notify if a resource completely download in nginx - nginx

Question

I need to know about full downloading a resource from server. My server is configured with NginX web server, and I want to do something if and only if the resource downloaded completely by user.

Answer 1

If you are using Nginx to handle downloading your files (using XSendfile), you should add a specific access_log block to your download handling block in your Nginx configs (in your "server" block). It would be something like this:
location /download_music/ {
internal;
root /usr/share/nginx/MY_SITE/media/music;
access_log /var/log/nginx/download.MY_SITE.log download;
}
The word "download" at the end of the access_log line is actually a log format which you should add it to the nginx main config file (/etc/nginx/nginx.conf) in the "http" block. It could be something like this:
http {
...
log_format download '{ "remote_addr" : "$remote_addr", "time":"$time_local", "request":"$request", '
'"traffic":$body_bytes_sent, "x_forwarded_for":"$http_x_forwarded_for" }';
...
}
You can change this format to what format you want (you will use it in your script later). If you monitor this log file (using "tail -f /var/log/nginx/download.MY_SITE.log") you will see that any time a download is paused or finished, a line of log will be added to this file.
The next step is using rsyslog and the "imfile" and "omprog" modules. You should add these configs at the end of the config file of rsyslog (/etc/rsyslog.conf):
$ModLoad imfile
$InputFileName /var/log/nginx/download.MY_SITE.log
$InputFileTag nginx-access
$InputFileStateFile state-nginx-access
$InputFileSeverity info
$InputFileFacility local3
$InputFilePollInterval 1
$InputRunFileMonitor
$ModLoad omprog
$actionomprogbinary /usr/share/nginx/MY_SITE/scripts/download.py
$template LogZillaDbInsert,"%hostname:::lowercase%\9%pri%\9%programname%\9%msg%\n"
local3.* :omprog:;RSYSLOG_TraditionalFileFormat
Pay attention to this line:
/usr/share/nginx/MY_SITE/scripts/download.py
This is the address of the script which would be called every time a log entry is added to the log file and the whole log entry will be available in this script using (in Python code):
line = sys.stdin.readline()
Then you can parse the line and find whatever you have logged including the downloaded file size (on every pause/finish event). Now, you can simply include the file size in the download URL and retrieve it in this script and compare it with the downloaded bytes. If these two numbers are equal, it means that download has been finished successfully. Moreover, you can do any other thing you want in this script (for example, expire download link, increase download count on DB, ...)