Support ETags at server level (#231)

Author: LeoColomb

.github/workflows/htaccess.yml

@@ -20,7 +20,7 @@ jobs:
         run: ./bin/build.sh test/conf/.htaccess test/build/htaccess_fixture.conf
 
       - name: Test with server-configs-test
-        uses: h5bp/server-configs-test@5.1.0
+        uses: h5bp/server-configs-test@5.2.0
         with:
           command: test
           server: httpd
@@ -29,7 +29,7 @@ jobs:
           tests: basic-file-access:cache-busting:custom-errors:forbidden-files:enforce-gzip:precompressed-files-gzip:concatenation
 
       - name: Benchmark
-        uses: h5bp/server-configs-test@5.1.0
+        uses: h5bp/server-configs-test@5.2.0
         with:
           command: benchmark
           server: httpd

.github/workflows/server.yml

@@ -31,18 +31,17 @@ jobs:
             "httpd.conf"
 
       - name: Test with server-configs-test
-        uses: h5bp/server-configs-test@5.1.0
+        uses: h5bp/server-configs-test@5.2.0
         with:
           command: test
           server: httpd
           root-path: /usr/local/apache2/htdocs
           certs-path: /usr/local/apache2/certs
           configs-volumes: test/vhosts:/usr/local/apache2/vhosts;h5bp:/usr/local/apache2/h5bp;httpd.conf:/usr/local/apache2/conf/httpd.conf
-          #tests: basic-file-access;caching;cache-busting;custom-errors;forbidden-files;enforce-gzip;precompressed-files-gzip;rewrites;ssl
-          tests: basic-file-access;cache-busting;custom-errors;forbidden-files;enforce-gzip;precompressed-files-gzip;rewrites;ssl
+          tests: basic-file-access;caching;cache-busting;custom-errors;forbidden-files;enforce-gzip;precompressed-files-gzip;rewrites;ssl
 
       - name: Benchmark
-        uses: h5bp/server-configs-test@5.1.0
+        uses: h5bp/server-configs-test@5.2.0
         with:
           command: benchmark
           server: httpd

bin/htaccess.conf

@@ -82,7 +82,7 @@ enable  "h5bp/web_performance/compression.conf"
 disable "h5bp/web_performance/pre-compressed_content_brotli.conf"
 disable "h5bp/web_performance/pre-compressed_content_gzip.conf"
 disable "h5bp/web_performance/content_transformation.conf"
-enable  "h5bp/web_performance/etags.conf"
+enable  "h5bp/web_performance/no_etags.conf"
 enable  "h5bp/web_performance/cache_expiration.conf"
 disable "h5bp/web_performance/file_concatenation.conf"
 disable "h5bp/web_performance/filename-based_cache_busting.conf"

h5bp/web_performance/etags.conf

@@ -2,15 +2,27 @@
 # | ETags                                                              |
 # ----------------------------------------------------------------------
 
-# Remove `ETags` as resources are sent with far-future expires headers.
+# Enable ETags.
+#
+# (1) Don't change the ETag on a compressed response.
+#     Default prevents serving "HTTP Not Modified" (304) responses to
+#     conditional requests for compressed content.
+#     https://httpd.apache.org/docs/current/mod/mod_deflate.html#deflatealteretag
+#
+# (2) `DeflateAlterETag` is not supported on version older than 2.5.
+#     As an alternative of the previous directive, this one is used to keep
+#     both the original ETag and the modified one when compressing responses.
+#     https://symfony.com/doc/current/http_cache/validation.html
 #
 # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag
-# https://developer.yahoo.com/performance/rules.html#etags
+# https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching
 # https://tools.ietf.org/html/rfc7232#section-2.3
+# https://httpd.apache.org/docs/current/mod/core.html#fileetag
+
+FileETag MTime Size
 
-# `FileETag None` doesn't work in all cases.
-<IfModule mod_headers.c>
-    Header unset ETag
-</IfModule>
+# (1)
+#DeflateAlterETag NoChange
 
-FileETag None
+# (2)
+RequestHeader edit "If-None-Match" '^"((.*)-gzip)"$' '"$1", "$2"'

h5bp/web_performance/no_etags.conf

@@ -0,0 +1,19 @@
+# ----------------------------------------------------------------------
+# | ETags                                                              |
+# ----------------------------------------------------------------------
+
+# Remove `ETags` as resources are sent with far-future expires headers.
+#
+# Apache `ETags` might have an unexpected behavior if `DeflateAlterETag`
+# can't be changed (which is the case at `.htaccess` level).
+#
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag
+# https://developer.yahoo.com/performance/rules.html#etags
+# https://tools.ietf.org/html/rfc7232#section-2.3
+
+# `FileETag None` doesn't work in all cases.
+<IfModule mod_headers.c>
+    Header unset ETag
+</IfModule>
+
+FileETag None

httpd.conf

@@ -154,6 +154,9 @@ EnableSendfile On
 # Enable gzip compression.
 Include h5bp/web_performance/compression.conf
 
+# Enable ETags validation.
+Include h5bp/web_performance/cache_expiration.conf
+
 # Specify file cache expiration.
 Include h5bp/web_performance/cache_expiration.conf
 

test/build/htaccess_fixture.conf

@@ -80,7 +80,7 @@ enable  "h5bp/web_performance/compression.conf"
 enable  "h5bp/web_performance/pre-compressed_content_brotli.conf"
 enable  "h5bp/web_performance/pre-compressed_content_gzip.conf"
 omit    "h5bp/web_performance/content_transformation.conf"
-enable  "h5bp/web_performance/etags.conf"
+enable  "h5bp/web_performance/no_etags.conf"
 enable  "h5bp/web_performance/cache_expiration.conf"
 enable  "h5bp/web_performance/file_concatenation.conf"
 enable  "h5bp/web_performance/filename-based_cache_busting.conf"