A strange problem about size limit in http header - http

Question

Context: I maintain a kind of web service server, but with a particular implementation: all data sent by the web services are located in the http header. That means there is only http header in the response (no body part). The web service runs as a windows service. The consumer is my PHP code which invokes the web service via CURL library. All this is in production since 3 years and works fine. I recently had to build a development environment.
I have the web service on a Windows 7 pro, as a windows service.
I have my PHP consumer in another windows 7 pro (WAMP + CURL).
my PHP code invokes the web service and displays the raw response.
in this context the problem occurs: if the response contains more than 1215 characters, I have an empty response (but no error message).
I installed my PHP code (exactly the same) on a new Linux ubuntu: I have the same problem.
I installed my PHP code (exactly the same) on a new Linux centos: I DON'T HAVE THE PROBLEM.
I read a lot on internet about size limitation on http header, and I think today it's not the reason of the problem.
I examined all size limitation parameters on Apache, PHP, Curl but I didn't find something relevant.
If someone has some information. All tracks are welcome. Thanks

Answer 1

not an answer, but want to say that using PHP 7.2.5 under mod_php with Apache 2.4.33, i am unable to reproduce your issue, as i have no problems sending anything from 1 byte to 10,000 to even 100,000 bytes in headers:
here is my producer.php:
<?php
$size=((int)($_GET['s'] ?? 1));
header("X-size: {$size}");
$data=str_repeat("a",$size);
header("X-data: {$data}");
http_response_code(204); // 204 NO CONTENT
and whether i hit http://127.0.0.1/producer.php?s=1 or http://127.0.0.1/producer.php?s=10000 or even http://127.0.0.1/producer.php?s=100000 , the data is returned without issue, as you can see in the screenshot above. can you reproduce the issue using my producer.php code?
btw, interestingly, when i try 1 million bytes, i get this error from curl:
$ curl -I http://127.0.0.1/producer.php?s=1000000
HTTP/1.1 204 No Content
Date: Wed, 16 Jan 2019 20:11:25 GMT
Server: Apache/2.4.33 (Win32) OpenSSL/1.1.0h PHP/7.2.5
X-Powered-By: PHP/7.2.5
X-size: 1000000
curl: (27) Rejected 104960 bytes header (max is 102400)!

Answer 2

Hanshenrik,
i also used CURLOPT_VERBOSE as you said. Here are the 2 curl logs.
The only difference is the line
<* stopped the pause stream!> in the Ubuntu curl log.
CURL log from Ubuntu witch has the probleme:
* Trying 192.168.1.205...
* TCP_NODELAY set
* Connected to 192.168.1.205 (192.168.1.205) port 8084 (#0)
> POST /datasnap/rest/TServerMethods/%22W_GetDashboard%22/ HTTP/1.1
Host: 192.168.1.205:8084
Accept-Encoding: gzip,deflate
Accept: application/json
Content-Type: text/xml; charset=utf-8
Pragma: dssession=146326.909376.656191
Content-Length: 15
* upload completely sent off: 15 out of 15 bytes
< HTTP/1.1 200 OK
< Connection: close
< Content-Encoding: deflate
< Content-Type: application/json
< Content-Length: 348
< Date: Thu, 17 Jan 2019 15:27:03 GMT
< Pragma: dssession=146326.909376.656191,dssessionexpires=3600000
<
* stopped the pause stream!
* Closing connection 0
CURL log from Centos witch has NOT the probleme:
* About to connect() to 192.168.1.205 port 8084 (#1)
* Trying 192.168.1.205...
* Connected to 192.168.1.205 (192.168.1.205) port 8084 (#1)
> POST /datasnap/rest/TServerMethods/%22W_GetDashboard%22/ HTTP/1.1
Host: 192.168.1.205:8084
Accept-Encoding: gzip,deflate
Accept: application/json
Content-Type: text/xml; charset=utf-8
Pragma: dssession=3812.553164.889594
Content-Length: 15
* upload completely sent off: 15 out of 15 bytes
< HTTP/1.1 200 OK
< Connection: close
< Content-Encoding: deflate
< Content-Type: application/json
< Content-Length: 348
< Date: Thu, 17 Jan 2019 15:43:39 GMT
< Pragma: dssession=3812.553164.889594,dssessionexpires=3600000
<
* Closing connection 1