Embedded trailer variables have no value

[kylesimon3@…]

Embedded trailer variables ($sent_trailer_ & $upstream_trailer_) for ngx_http_upstream_module and ngx_http_headers_module do not have any value.

Using the directive:
add_trailer X-TestTrailer $sent_trailer_x_testtrailer
OR
add_trailer X-TestTrailer $upstream_trailer_x_testtrailer

Is not working when the upstream server sends an Http trailer with the name X-TestTrailer.

In testing we've found that add_trailer is working, but the embedded variables do not have values from the upstream response trailers.

Reproducible POC:

Spin up a simple server that serves a trailer in every response. A simple node app like so works just fine:

var http = require('http');
var fs = require('fs');

var server = http.createServer(function(req, res) {
  console.log('request was made: ' + req.url);
  res.writeHead(200, {'Content-Type': 'application/json'});
  res.addTrailers({'X-TestTrailer': 'This is a trailer message'});
  res.end('End of Response');
});

server.listen(3000, '127.0.0.1');
console.log('listening on port 3000');

In the nginx.conf file under your server (should point to the sample app), add:
add_trailer X-TestTrailer $sent_trailer_x_testtrailer;
AND
add_trailer X-UpstreamTestTrailer $upstream_trailer_x_testtrailer;

Start nginx

Make a request directly to the app server ( you can use curl with the --raw argument to see trailers ) note the trailers are received.

Make the same request to the nginx proxy and note the trailers are not received.

[tammy annette harrell]

ATOM

[Roman Arutyunyan]

Only ngx_http_grpc_module / grpc_pass currently supports trailers. If you use proxy_pass, trailers will not work.