now we check response header Content-Encoding by default and a non-empty header value will skip srcache_store; also introduced a new directive named srcache_ignore_content_encoding to ignore this response header.

Author: agentzh

src/ngx_http_srcache_filter_module.c

@@ -143,6 +143,13 @@ static ngx_command_t  ngx_http_srcache_commands[] = {
       offsetof(ngx_http_srcache_loc_conf_t, store_no_cache),
       NULL },
 
+    { ngx_string("srcache_ignore_content_encoding"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_srcache_loc_conf_t, ignore_content_encoding),
+      NULL },
+
       ngx_null_command
 };
 
@@ -291,9 +298,21 @@ ngx_http_srcache_header_filter(ngx_http_request_t *r)
     }
 #endif
 
+    if (!slcf->ignore_content_encoding && r->headers_out.content_encoding
+        && r->headers_out.content_encoding->value.len)
+    {
+        ngx_log_error(NGX_LOG_WARN, r->connection->log, 0,
+                "srcache_store skipped due to response header "
+                "\"Content-Encoding: %V\" (maybe you forgot to disable "
+                "compression on the backend?)",
+                &r->headers_out.content_encoding->value);
+
+        return ngx_http_next_header_filter(r);
+    }
+
     if (ngx_http_srcache_response_no_cache(r, slcf) == NGX_OK) {
         ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
-                "srcache_store skipped due to response Cache-Control setting");
+                "srcache_store skipped due to response header Cache-Control");
 
         return ngx_http_next_header_filter(r);
     }
@@ -621,6 +640,7 @@ ngx_http_srcache_create_loc_conf(ngx_conf_t *cf)
     conf->store_private = NGX_CONF_UNSET;
     conf->store_no_store = NGX_CONF_UNSET;
     conf->store_no_cache = NGX_CONF_UNSET;
+    conf->ignore_content_encoding = NGX_CONF_UNSET;
 
     return conf;
 }
@@ -658,6 +678,7 @@ ngx_http_srcache_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_value(conf->store_private, prev->store_private, 0);
     ngx_conf_merge_value(conf->store_no_store, prev->store_no_store, 0);
     ngx_conf_merge_value(conf->store_no_cache, prev->store_no_cache, 0);
+    ngx_conf_merge_value(conf->ignore_content_encoding, prev->ignore_content_encoding, 0);
 
     return NGX_CONF_OK;
 }

src/ngx_http_srcache_filter_module.h

@@ -37,6 +37,7 @@ typedef struct {
     ngx_flag_t                       store_private;
     ngx_flag_t                       store_no_store;
     ngx_flag_t                       store_no_cache;
+    ngx_flag_t                       ignore_content_encoding;
 
     unsigned              postponed_to_access_phase_end;
 } ngx_http_srcache_loc_conf_t;

t/gzip.t

@@ -0,0 +1,161 @@
+# vi:filetype=
+
+use lib 'lib';
+use Test::Nginx::Socket;
+
+#repeat_each(2);
+
+plan tests => repeat_each() * 4 * blocks();
+
+$ENV{TEST_NGINX_MEMCACHED_PORT} ||= 11211;
+
+#master_on();
+no_shuffle();
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: flush all
+--- config
+    location /flush {
+        set $memc_cmd 'flush_all';
+        memc_pass 127.0.0.1:$TEST_NGINX_MEMCACHED_PORT;
+    }
+--- response_headers
+Content-Type: text/plain
+Content-Length: 4
+--- request
+GET /flush
+--- response_body eval: "OK\r\n"
+
+
+
+=== TEST 2: basic fetch (cache miss), and not stored due to Content-Encoding
+--- config
+    location /foo {
+        default_type text/css;
+        srcache_fetch GET /memc $uri;
+        srcache_store PUT /memc $uri;
+
+        content_by_lua '
+            ngx.header.content_encoding = "gzip"
+            ngx.say("hello")
+        ';
+    }
+
+    location /memc {
+        internal;
+
+        set $memc_key $query_string;
+        set $memc_exptime 300;
+        memc_pass 127.0.0.1:$TEST_NGINX_MEMCACHED_PORT;
+    }
+--- request
+GET /foo
+--- response_headers
+Content-Length:
+Content-Encoding: gzip
+--- response_body
+hello
+
+
+
+=== TEST 3: basic fetch (cache miss again, not stored in the previous case)
+--- config
+    location /foo {
+        default_type text/css;
+        srcache_fetch GET /memc $uri;
+        srcache_store PUT /memc $uri;
+
+        echo world;
+    }
+
+    location /memc {
+        internal;
+
+        set $memc_key $query_string;
+        set $memc_exptime 300;
+        memc_pass 127.0.0.1:$TEST_NGINX_MEMCACHED_PORT;
+    }
+--- request
+GET /foo
+--- response_headers
+Content-Type: text/css
+Content-Length: 
+--- response_body
+world
+
+
+
+=== TEST 4: flush all
+--- config
+    location /flush {
+        set $memc_cmd 'flush_all';
+        memc_pass 127.0.0.1:$TEST_NGINX_MEMCACHED_PORT;
+    }
+--- response_headers
+Content-Type: text/plain
+Content-Length: 4
+--- request
+GET /flush
+--- response_body eval: "OK\r\n"
+
+
+
+=== TEST 5: basic fetch (cache miss), and stored due to Content-Encoding + srcache_ignore_content_encoding
+--- config
+    location /foo {
+        default_type text/css;
+        srcache_fetch GET /memc $uri;
+        srcache_store PUT /memc $uri;
+        srcache_ignore_content_encoding on;
+
+        content_by_lua '
+            ngx.header.content_encoding = "gzip"
+            ngx.say("hello")
+        ';
+    }
+
+    location /memc {
+        internal;
+
+        set $memc_key $query_string;
+        set $memc_exptime 300;
+        memc_pass 127.0.0.1:$TEST_NGINX_MEMCACHED_PORT;
+    }
+--- request
+GET /foo
+--- response_headers
+Content-Length:
+Content-Encoding: gzip
+--- response_body
+hello
+
+
+
+=== TEST 6: basic fetch (cache miss again, not stored in the previous case)
+--- config
+    location /foo {
+        default_type text/css;
+        srcache_fetch GET /memc $uri;
+        srcache_store PUT /memc $uri;
+
+        echo world;
+    }
+
+    location /memc {
+        internal;
+
+        set $memc_key $query_string;
+        set $memc_exptime 300;
+        memc_pass 127.0.0.1:$TEST_NGINX_MEMCACHED_PORT;
+    }
+--- request
+GET /foo
+--- response_headers
+Content-Type: text/css
+Content-Length: 6
+--- response_body
+hello
+