With Apache httpd 2.2, it was possible to setup a reverse proxy and use mod_deflate for compressing proxied content, honoring Accept-Encoding: gzip headers.
This configuration was sufficient for getting it to work:
LoadModule deflate_module modules/mod_deflate.so
LoadModule filter_module modules/mod_filter.so
SetOutputFilter DEFLATE
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
ProxyRequests Off
ProxyPass /tomcat http://localhost:8880/
ProxyPassReverse /tomcat http://localhost:8880/
ProxyPass /other http://localhost:8001/
ProxyPassReverse /other http://localhost:8001/
Now after upgrading to 2.4 (2.4.29 on Windows), that same configuration is accepted, and it indeed compresses static content served from DocumentRoot. But the same content is returned uncompressed, when retrieved via ProxyPass.
I know that I can configure Tomcat to do the compression, but there is also this other server that just ignores Accept-Encoding headers.
How can I set up a reverse proxy, and have proxied content compressed?
Edit:
Here are the headers returned, demonstrating that proxied content is not compressed by the 2.4 server:
----- Retrieving uncompressed from DocumentRoot ---------------------------------
C:\Temp>curl -I http://localhost/test.txt
HTTP/1.1 200 OK
Date: Tue, 09 Jan 2018 17:11:59 GMT
Server: Apache/2.4.29 (Win64) OpenSSL/1.1.0g
Last-Modified: Fri, 05 Jan 2018 12:58:40 GMT
ETag: "75441-5620701eb471c"
Accept-Ranges: bytes
Content-Length: 480321
Vary: Accept-Encoding
Content-Type: text/plain
----- The same from Tomcat ------------------------------------------------------
C:\Temp>curl -I http://localhost:8880/rr/test.txt
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
ETag: W/"480321-1515157120042"
Last-Modified: Fri, 05 Jan 2018 12:58:40 GMT
Content-Type: text/plain
Content-Length: 480321
Date: Tue, 09 Jan 2018 17:11:59 GMT
----- 2.4.29: Retrieving compressed from DocumentRoot ---------------------------
C:\Temp>curl -I -H "Accept-Encoding: gzip" http://localhost/test.txt
HTTP/1.1 200 OK
Date: Tue, 09 Jan 2018 17:11:59 GMT
Server: Apache/2.4.29 (Win64) OpenSSL/1.1.0g
Last-Modified: Fri, 05 Jan 2018 12:58:40 GMT
ETag: "75441-5620701eb471c-gzip"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 48265
Content-Type: text/plain
----- 2.4.29: Not getting any compression for proxied Tomcat content ------------
C:\Temp>curl -I -H "Accept-Encoding: gzip" http://localhost/tomcat/rr/test.txt
HTTP/1.1 200 OK
Date: Tue, 09 Jan 2018 17:11:59 GMT
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
ETag: W/"480321-1515157120042"
Last-Modified: Fri, 05 Jan 2018 12:58:40 GMT
Content-Type: text/plain
Content-Length: 480321
----- 2.2.14: Retrieving compressed from DocumentRoot ---------------------------
C:\Temp>curl -I -H "Accept-Encoding: gzip" http://localhost:81/test.txt
HTTP/1.1 200 OK
Date: Tue, 09 Jan 2018 17:11:59 GMT
Server: Apache/2.2.14 (Win32)
Last-Modified: Fri, 05 Jan 2018 12:58:40 GMT
ETag: "90000000e7463-75441-5620701eb471c"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 48265
Content-Type: text/plain
----- 2.2.14: Proxied Tomcat content comes compressed ---------------------------
C:\Temp>curl -I -H "Accept-Encoding: gzip" http://localhost:81/tomcat/rr/test.txt
HTTP/1.1 200 OK
Date: Tue, 09 Jan 2018 17:11:59 GMT
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
ETag: W/"480321-1515157120042"
Last-Modified: Fri, 05 Jan 2018 12:58:40 GMT
Content-Type: text/plain
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 20
All of this was tested on a plain 2.4.29 installation downloaded from ApacheHaus. The above configuration has been added to httpd.conf, nothing else has been changed. The same applies to the 2.2.14 installation (downloaded in 2009 from Apache), but that one was additionally changed to port 81.
I’ve managed to reproduce curl + apache/tomcat behavior that you described
This is how I reproduced it (OS X El Capitan):
Tomcat:
docker run -it --rm -p 8880:8080 tomcat:6.0
Apache
httpd -v
Server version: Apache/2.4.18 (Unix)
Server built: Feb 20 2016 20:03:19
httpd -l
Compiled in modules:
core.c
mod_so.c
http_core.c
prefork.c
Apache config (in its entirety):
Listen 80
LoadModule authz_user_module libexec/apache2/mod_authz_user.so
LoadModule authz_core_module libexec/apache2/mod_authz_core.so
LoadModule access_compat_module libexec/apache2/mod_access_compat.so
LoadModule filter_module libexec/apache2/mod_filter.so
LoadModule deflate_module libexec/apache2/mod_deflate.so
LoadModule mime_module libexec/apache2/mod_mime.so
LoadModule log_config_module libexec/apache2/mod_log_config.so
LoadModule headers_module libexec/apache2/mod_headers.so
LoadModule version_module libexec/apache2/mod_version.so
LoadModule proxy_module libexec/apache2/mod_proxy.so
LoadModule proxy_http_module libexec/apache2/mod_proxy_http.so
LoadModule unixd_module libexec/apache2/mod_unixd.so
<IfModule unixd_module>
User _www
Group _www
</IfModule>
<IfModule mime_module>
TypesConfig /private/etc/apache2/mime.types
</IfModule>
LogLevel debug
<IfModule log_config_module>
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
<IfModule logio_module>
# You need to enable mod_logio.c to use %I and %O
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
</IfModule>
CustomLog "/private/var/log/apache2/access_log" common
</IfModule>
ErrorLog "/private/var/log/apache2/error_log"
TraceEnable off
SetOutputFilter DEFLATE
ProxyRequests Off
ProxyPass /tomcat http://localhost:8880/
ProxyPassReverse /tomcat http://localhost:8880/
ProxyPass /other http://localhost:8001/
ProxyPassReverse /other http://localhost:8001/
DocumentRoot /Library/WebServer/Documents
curl -I -H 'Accept-Encoding: gzip' 'http://localhost/tomcat'
HTTP/1.1 200 OK
Date: Sat, 13 Jan 2018 13:35:14 GMT
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
ETag: W/"7454-1491118183000"
Last-Modified: Sun, 02 Apr 2017 07:29:43 GMT
Content-Type: text/html
Content-Length: 7454
curl -I -H 'Accept-Encoding: gzip' 'http://localhost/index.html.en'
HTTP/1.1 200 OK
Date: Sat, 13 Jan 2018 13:35:25 GMT
Server: Apache/2.4.18 (Unix)
Last-Modified: Tue, 09 Jan 2018 04:51:20 GMT
ETag: "45-56250aa712200-gzip"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 65
Content-Type: text/html
As you can see, the output very closely matches your example
If I use a regular GET request instead of HEAD (via browser or curl without -I) tomcat’s response DOES GETS GZIPPED
curl -D - -H 'Accept-Encoding: gzip' 'http://localhost/tomcat' 2>/dev/null | strings
HTTP/1.1 200 OK
Date: Sat, 13 Jan 2018 13:37:19 GMT
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
ETag: W/"7454-1491118183000-gzip"
Last-Modified: Sun, 02 Apr 2017 07:29:43 GMT
Content-Type: text/html
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 2526
(some junk)
No idea why it’s happening though, looks like Apache’s + mod_proxy/defate misbehavior on HEAD requests. If you're saying it was OK in Apache 2.2 I would guess it might be somehow related to this adjustment
mod_deflate will now skip compression if it knows that the size overhead added by the compression is larger than the data to be compressed.
So I’d check whether the problem persists for GET requests in your case. If yes - provide even more details on your setup so that your environment could be 100% replicated - valid Dockerfile for apache and tomcat to isolate a likely environment discrepancy would be fine