HEAD / don't close response

[Wing924]

Elasticsearch version (bin/elasticsearch --version):
6.4.0 (rpm version)
Plugins installed: []
none
JVM version (java -version):
openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
OS version (uname -a if on a Unix-like system):
Linux myhostname 3.10.0-693.11.6.el7.x86_64 #1 SMP Thu Jan 4 01:06:37 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Description of the problem including expected versus actual behavior:
HEAD / returns 200 OK, not connection never be closed.
Steps to reproduce:

$ curl -vs -XHEAD http://localhost:9200
* About to connect() to localhost port 9200 (#0)
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9200 (#0)
> HEAD / HTTP/1.1
> User-Agent: curl/7.29.0
> Host: localhost:9200
> Accept: */*
>
< HTTP/1.1 200 OK
< content-type: application/json; charset=UTF-8
< content-length: 511
<

# hang up here

Provide logs (if relevant):

[danielmitterdorfer]

Thanks for your report. However, the problem here is curl. You need to use --head instad of -XHEAD to get curl to behave properly. To quote the man page:

This option only changes the actual word used in the HTTP
request, it does not alter the way curl behaves. So for example
if you want to make a proper HEAD request, using -X HEAD will
not suffice. You need to use the -I, --head option.

See also https://daniel.haxx.se/blog/2015/09/11/unnecessary-use-of-curl-x/ for further info.

[Wing924]

@danielmitterdorfer Thank you.