Nginx – Passing a timestamp header onto upstream servers with Nginx

nginx

I'd like to have my Nginx load balancer send a timestamp in a header onto the upstream servers.

I tried something like this:

proxy_set_header X-Start-Time $msec;

Of course, $msec is a log variable and Nginx gives an error:

Restarting nginx: [emerg]: unknown "msec" variable

Best Answer

$msec is indeed a variable that lives only during log writing.

The easiest solution would be to build Nginx with Perl module and define a variable backed by Perl subroutine:

# at 'http' context
perl_set $unix_timestamp 'sub {
  time();
}';

# where you want it:
proxy_set_header X-Start-Time $unix_timestamp;

Related Solutions

Nginx: try next upstream on http 200 response with custom header set

There's no option for proxy_next_upstream to implement the behavior you describe.

Your application should not return an HTTP 200 if it couldn't actually process the request. Have the application return a more appropriate error, such as 500 or 503.

Nginx add header conditional on an upstream_http_ variable

This doesn't work because the if is evaluated before the request is passed to the backend, so the $upstream_http_ variables don't have any values yet. add_header with an empty value is ignored, so you can use a map to conditionally add the header like so:

map $upstream_http_strict_transport_security $sts {
  '' max-age=15552000;
}

server {
  location / {
    add_header Strict-Transport-Security $sts;
  }
}

Best Answer

Related Solutions

Nginx: try next upstream on http 200 response with custom header set

Nginx add header conditional on an upstream_http_ variable

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