Fixes Accept-Encoding cache variance behavior

Changes the condition to only ignore Accept-Encoding variance when explicitly set to 1, preserving proper Vary header semantics for the default value of 2.

Updates test expectations to reflect correct cache miss behavior when different Accept-Encoding variants are requested, ensuring each encoding type gets its own cache entry with appropriate Content-Encoding headers.

Author: JakeChampion

src/iocore/cache/HttpTransactCache.cc

@@ -1244,7 +1244,11 @@ HttpTransactCache::CalcVariability(const HttpConfigAccessor *http_config_params,
 
         // Disable Vary mismatch checking for Accept-Encoding.  This is only safe to
         // set if you are promising to fix any Accept-Encoding/Content-Encoding mismatches.
-        if (http_config_params->get_ignore_accept_encoding_mismatch() &&
+        // Only suppress variability checks when the operator explicitly set
+        // proxy.config.http.cache.ignore_accept_encoding_mismatch to 1. The
+        // documented default value of 2 should continue to enforce Vary header
+        // semantics whenever the origin sends one.
+        if ((http_config_params->get_ignore_accept_encoding_mismatch() == 1) &&
             !strcasecmp(const_cast<char *>(field->str), "Accept-Encoding")) {
           continue;
         }

tests/gold_tests/headers/normalized_ae_match_vary_cache.test.py

@@ -31,6 +31,37 @@
 replay_file = "replays/normalized_ae_varied_transactions.replay.yaml"
 server = Test.MakeVerifierServerProcess("server", replay_file)
 
+# Verify that cache hit requests never reach the server
+# Case 2 (normalize_ae:1) cache hits
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 12", "Verify empty Accept-Encoding (uuid 12) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 13", "Verify deflate request (uuid 13) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 14", "Verify br,compress request (uuid 14) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 16", "Verify br,compress,gzip request (uuid 16) is a cache hit and doesn't reach the server.")
+# Case 3 (normalize_ae:2) cache hits
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 22", "Verify empty Accept-Encoding (uuid 22) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 23", "Verify deflate request (uuid 23) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 26", "Verify br,compress,gzip request (uuid 26) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 27", "Verify compress,gzip request (uuid 27) is a cache hit and doesn't reach the server.")
+# Case 4 (normalize_ae:3) cache hits
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 32", "Verify empty Accept-Encoding (uuid 32) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 33", "Verify deflate request (uuid 33) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 37", "Verify compress,gzip request (uuid 37) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 38", "Verify br;q=1.1 request (uuid 38) is a cache hit and doesn't reach the server.")
+server.Streams.stdout += Testers.ExcludesExpression(
+    "uuid: 39", "Verify br,gzip;q=0.8 request (uuid 39) is a cache hit and doesn't reach the server.")
+
 ts = Test.MakeATSProcess("ts", enable_cache=True)
 ts.Disk.remap_config.AddLine(
     f"map http://www.ae-0.com http://127.0.0.1:{server.Variables.http_port}" +

tests/gold_tests/headers/replays/normalized_ae_varied_transactions.replay.yaml

@@ -96,7 +96,7 @@ sessions:
         - [ X-Response-Identifier, { value: Empty-Accept-Encoding, as: equal } ]
         - [ X-Cache, { value: miss, as: equal } ]
 
-  # Accept-Encoding header deflate would match the alternate of empty Accept-Encoding header
+  # request deflate Accept-Encoding when origin lacks that variant
   - client-request:
       method: "GET"
       version: "1.1"
@@ -113,13 +113,12 @@ sessions:
       <<: *404_response
 
     proxy-response:
-      status: 200
+      status: 404
       headers:
         fields:
-        - [ X-Response-Identifier, { value: Empty-Accept-Encoding, as: equal } ]
-        - [ X-Cache, { value: hit-fresh, as: equal } ]
+        - [ X-Cache, { value: miss, as: equal } ]
 
-  # Accept-Encoding header br, compress would match the alternate of empty Accept-Encoding header
+  # load an alternate of br Accept-Encoding header
   - client-request:
       method: "GET"
       version: "1.1"
@@ -133,14 +132,23 @@ sessions:
       delay: 100ms
 
     server-response:
-      <<: *404_response
+      status: 200
+      reason: OK
+      headers:
+        fields:
+        - [ Transfer-Encoding, chunked ]
+        - [ Cache-Control, max-age=300 ]
+        - [ Content-Encoding, br ]
+        - [ Vary, Accept-Encoding ]
+        - [ Connection, close ]
+        - [ X-Response-Identifier, Br-Accept-Encoding ]
 
     proxy-response:
       status: 200
       headers:
         fields:
-        - [ X-Response-Identifier, { value: Empty-Accept-Encoding, as: equal } ]
-        - [ X-Cache, { value: hit-fresh, as: equal } ]
+        - [ X-Response-Identifier, { value: Br-Accept-Encoding, as: equal } ]
+        - [ X-Cache, { value: miss, as: equal } ]
 
   # load an alternate of gzip Accept-Encoding header
   - client-request:
@@ -176,7 +184,7 @@ sessions:
         - [ X-Response-Identifier, { value: Gzip-Accept-Encoding, as: equal } ]
         - [ X-Cache, { value: miss, as: equal } ]
 
-  # Accept-Encoding header br, compress, gzip would match the alternate of gzip Accept-Encoding header
+  # load an alternate of br Accept-Encoding header
   - client-request:
       method: "GET"
       version: "1.1"
@@ -190,14 +198,23 @@ sessions:
       delay: 100ms
 
     server-response:
-      <<: *404_response
+      status: 200
+      reason: OK
+      headers:
+        fields:
+        - [ Transfer-Encoding, chunked ]
+        - [ Cache-Control, max-age=300 ]
+        - [ Content-Encoding, br ]
+        - [ Vary, Accept-Encoding ]
+        - [ Connection, close ]
+        - [ X-Response-Identifier, Br-Accept-Encoding ]
 
     proxy-response:
       status: 200
       headers:
         fields:
-        - [ X-Response-Identifier, { value: Gzip-Accept-Encoding, as: equal } ]
-        - [ X-Cache, { value: hit-fresh, as: equal } ]
+        - [ X-Response-Identifier, { value: Br-Accept-Encoding, as: equal } ]
+        - [ X-Cache, { value: miss, as: equal } ]
 
 
   # Case 2 proxy.config.http.normalize_ae:1
@@ -699,10 +716,6 @@ sessions:
         - [ X-Response-Identifier, { value: Gzip-Accept-Encoding, as: equal } ]
         - [ X-Cache, { value: miss, as: equal } ]
 
-  # NOTICE: This case should load an alternate of br, gzip Accept-Encoding header.
-  #         However, due to the implementation of calculate_quality_of_match(),
-  #         ATS matches the alternate of gzip Accept-Encoding header.
-  #         The result is DIFFERENT from the description of proxy.config.http.normalize_ae: 3
   - client-request:
       method: "GET"
       version: "1.1"
@@ -733,10 +746,8 @@ sessions:
       status: 200
       headers:
         fields:
-        # - [ X-Response-Identifier, { value: Br-Gzip-Accept-Encoding, as: equal } ]
-        # - [ X-Cache, { value: miss, as: equal } ]
-        - [ X-Response-Identifier, { value: Gzip-Accept-Encoding, as: equal } ]
-        - [ X-Cache, { value: hit-fresh, as: equal } ]
+        - [ X-Response-Identifier, { value: Br-Gzip-Accept-Encoding, as: equal } ]
+        - [ X-Cache, { value: miss, as: equal } ]
 
   # Accept-Encoding header compress, gzip would match the alternate of gzip Accept-Encoding header
   - client-request:
@@ -784,11 +795,6 @@ sessions:
         - [ X-Response-Identifier, { value: Br-Accept-Encoding, as: equal } ]
         - [ X-Cache, { value: hit-fresh, as: equal } ]
 
-  # NOTICE: This case should make Accept-Encoding header br, gzip;q=0.8 match
-  #         the alternate of br, gzip Accept-Encoding header.
-  #         However, due to the implementation of calculate_quality_of_match(),
-  #         ATS matches the alternate of gzip Accept-Encoding header.
-  #         The result is DIFFERENT from the description of proxy.config.http.normalize_ae: 3
   - client-request:
       method: "GET"
       version: "1.1"
@@ -808,6 +814,5 @@ sessions:
       status: 200
       headers:
         fields:
-        # - [ X-Response-Identifier, { value: Br-Gzip-Accept-Encoding, as: equal } ]
-        - [ X-Response-Identifier, { value: Gzip-Accept-Encoding, as: equal } ]
+        - [ X-Response-Identifier, { value: Br-Gzip-Accept-Encoding, as: equal } ]
         - [ X-Cache, { value: hit-fresh, as: equal } ]