caddy-frontend: Implement prefer-gzip-encoding-to-backend

Desipte of original analysis the middleware plugin is not needed, as Caddy's
http.rewrite + http.proxy is powerful enough to set headers depending on the
header regular expression.

software/caddy-frontend/TODO.rst

@@ -6,9 +6,6 @@ Generally things to be done with ``caddy-frontend``:
 
    * **Jérome Perrin**: *For event source, if I understand https://github.com/mholt/caddy/issues/1355 correctly, we could use caddy as a proxy in front of nginx-push-stream . If we have a "central shared" caddy instance, can it handle keeping connections opens for many clients ?*
  * ``ssl_ca_crt``
- * ``prefer-gzip-encoding-to-backend`` (requires writing middleware plugin for Caddy)::
-
-    RequestHeader edit Accept-Encoding "(^gzip,.*|.*, gzip,.*|.*, gzip$|^gzip$)" "gzip"
  * ``disabled-cookie-list`` (requires writing middleware plugin for Caddy)::
 
     RequestHeader edit Cookie "(^%(disabled_cookie)s=[^;]*; |; %(disabled_cookie)s=[^;]*|^%(disabled_cookie)s=[^;]*$)" ""' % dict(disabled_cookie=disabled_cookie)  }}

software/caddy-frontend/buildout.hash.cfg

@@ -50,7 +50,7 @@ md5sum = f20d6c3d2d94fb685f8d26dfca1e822b
 
 [template-default-slave-virtualhost]
 filename = templates/default-virtualhost.conf.in
-md5sum = aca244bf8792793800895bf2e5310787
+md5sum = 6da56d875f5cf396f8fd0685cf1a9a7a
 
 [template-cached-slave-virtualhost]
 filename = templates/cached-virtualhost.conf.in

software/caddy-frontend/templates/default-virtualhost.conf.in

@@ -2,6 +2,10 @@
 {%- set disable_no_cache_header = ('' ~ slave_parameter.get('disable-no-cache-request', '')).lower() in TRUE_VALUES %}
 {%- set disable_via_header = ('' ~ slave_parameter.get('disable-via-header', '')).lower() in TRUE_VALUES %}
 {%- set prefer_gzip = ('' ~ slave_parameter.get('prefer-gzip-encoding-to-backend', '')).lower() in TRUE_VALUES %}
+{%- set proxy_append_list = [('', 'Default proxy configuration')] %}
+{%- if prefer_gzip %}
+{%- do proxy_append_list.append(('prefer-gzip', 'Proxy which always overrides Accept-Encoding to gzip if such is found')) %}
+{%- endif %} {#- if prefer_gzip #}
 {%- set server_alias_list =  slave_parameter.get('server-alias', '').split() %}
 {%- set enable_h2 = ('' ~ slave_parameter.get('enable-http2', slave_parameter['enable_http2_by_default'])).lower() in TRUE_VALUES %}
 {%- set ssl_proxy_verify = ('' ~ slave_parameter.get('ssl-proxy-verify', '')).lower() in TRUE_VALUES %}
@@ -45,11 +49,21 @@
 {%- endfor %} {#- for disabled_cookie in disabled_cookie_list #}
 
 {%- if prefer_gzip %}
+  rewrite {
+    if {>Accept-Encoding} match "(^gzip,.*|.*, gzip,.*|.*, gzip$|^gzip$)"
+    to /prefer-gzip{uri}
+  }
 {%- endif %} {#- if prefer_gzip #}
 
 {%- if slave_type ==  'zope' and backend_url %}
   # Zope configuration
-  proxy / {{ backend_url }} {
+{%-   for (proxy_name, proxy_comment) in proxy_append_list %}
+  # {{ proxy_comment }}
+  proxy /{{ proxy_name }} {{ backend_url }} {
+{%-     if proxy_name == 'prefer-gzip' %}
+    without /prefer-gzip
+    header_upstream Accept-Encoding gzip
+{%-     endif %} {#-     if proxy_name == 'prefer-gzip' #}
     # As backend is trusting REMOTE_USER header unset it always
     header_upstream -REMOTE_USER
 
@@ -70,6 +84,7 @@
     insecure_skip_verify
 {%-   endif %} {#-   if ssl_proxy_verify #}
   } {# proxy #}
+{%-   endfor %} {#-   for (proxy_name, proxy_comment) in proxy_append_list #}
   {%- if 'default-path' in slave_parameter %}
   redir 301 {
     if {path} is /
@@ -95,7 +110,13 @@
 {%-   endif %} {#-   if 'default-path' in slave_parameter #}
 {%-   if backend_url %}
 
-  proxy / {{ backend_url }} {
+{%-   for (proxy_name, proxy_comment) in proxy_append_list %}
+  # {{ proxy_comment }}
+  proxy /{{ proxy_name }} {{ backend_url }} {
+{%-     if proxy_name == 'prefer-gzip' %}
+    without /prefer-gzip
+    header_upstream Accept-Encoding gzip
+{%-     endif %} {#-     if proxy_name == 'prefer-gzip' #}
     # As backend is trusting REMOTE_USER header unset it always
     header_upstream -REMOTE_USER
 
@@ -116,6 +137,7 @@
     insecure_skip_verify
 {%-     endif %} {#-     if ssl_proxy_verify #}
   }  {# proxy #}
+{%-    endfor %} {#-   for (proxy_name, proxy_comment) in proxy_append_list #}
 {%-   endif %} {#-   if backend_url #}
 {%- endif %} {#- if slave_type ==  'zope' and backend_url #}
 }  {# https_host_list|join(', ') #}
@@ -136,6 +158,10 @@
 {%- endfor %} {#- for disabled_cookie in disabled_cookie_list #}
 
 {%- if prefer_gzip %}
+  rewrite {
+    if {>Accept-Encoding} match "(^gzip,.*|.*, gzip,.*|.*, gzip$|^gzip$)"
+    to /prefer-gzip{uri}
+  }
 {%- endif %} {#- if prefer_gzip #}
 
 {%- if https_only %}
@@ -148,7 +174,13 @@
   } {# redir #}
 {%- elif slave_type ==  'zope' and backend_url %} {#- if https_only #}
   # Zope configuration
-  proxy / {{ backend_url }} {
+{%-   for (proxy_name, proxy_comment) in proxy_append_list %}
+  # {{ proxy_comment }}
+  proxy /{{ proxy_name }} {{ backend_url }} {
+{%-     if proxy_name == 'prefer-gzip' %}
+    without /prefer-gzip
+    header_upstream Accept-Encoding gzip
+{%-     endif %} {#-     if proxy_name == 'prefer-gzip' #}
     # As backend is trusting REMOTE_USER header unset it always
     header_upstream -REMOTE_USER
 
@@ -169,6 +201,7 @@
     insecure_skip_verify
 {%-   endif %} {#-   if ssl_proxy_verify #}
   } {# proxy #}
+{%- endfor %} {#-   for (proxy_name, proxy_comment) in proxy_append_list #}
 {%-   if 'default-path' in slave_parameter %}
   redir 301 {
     if {path} is /
@@ -188,7 +221,13 @@
   } {# redir #}
 {%-   endif %} {#-   if 'default-path' in slave_parameter #}
 {%-   if slave_parameter.get('url', '') %}
-  proxy / {{ slave_parameter.get('url', '') }} {
+{%-   for (proxy_name, proxy_comment) in proxy_append_list %}
+  # {{ proxy_comment }}
+  proxy /{{ proxy_name }} {{ slave_parameter.get('url', '') }} {
+{%-     if proxy_name == 'prefer-gzip' %}
+    without /prefer-gzip
+    header_upstream Accept-Encoding gzip
+{%-     endif %} {#-     if proxy_name == 'prefer-gzip' #}
     # As backend is trusting REMOTE_USER header unset it always
     header_upstream -REMOTE_USER
 
@@ -209,6 +248,7 @@
     insecure_skip_verify
 {%-     endif %} {#-     if ssl_proxy_verify #}
   } {# proxy #}
+{%-    endfor %} {#-   for (proxy_name, proxy_comment) in proxy_append_list #}
 {%-   endif %} {#-   if slave_parameter.get('url', '') #}
 {%- endif %} {#- if https_only #}
 } {# http_host_list|join(', ') #}