fix(proxy-cache): keep different strategy response header consistency (#11048)

Author: theweakgod

apisix/plugins/proxy-cache/memory.lua

@@ -52,14 +52,17 @@ function _M:get(key)
     end
 
     -- If the key does not exist or has expired, then res_json will be nil.
-    local res_json, err = self.dict:get(key)
+    local res_json, err, stale = self.dict:get_stale(key)
     if not res_json then
         if not err then
             return nil, "not found"
         else
             return nil, err
         end
     end
+    if stale then
+        return nil, "expired"
+    end
 
     local res_obj, err = core.json.decode(res_json)
     if not res_obj then

apisix/plugins/proxy-cache/memory_handler.lua

@@ -213,11 +213,19 @@ function _M.access(conf, ctx)
     end
 
     if err then
-        core.response.set_header("Apisix-Cache-Status", "MISS")
-        if err ~= "not found" then
+        if err == "expired" then
+            core.response.set_header("Apisix-Cache-Status", "EXPIRED")
+
+        elseif err ~= "not found" then
+            core.response.set_header("Apisix-Cache-Status", "MISS")
             core.log.error("failed to get from cache, err: ", err)
+
         elseif conf.cache_control and cc["only-if-cached"] then
+            core.response.set_header("Apisix-Cache-Status", "MISS")
             return 504
+
+        else
+            core.response.set_header("Apisix-Cache-Status", "MISS")
         end
         return
     end

t/plugin/proxy-cache/memory.t

@@ -506,7 +506,7 @@ GET /hello
 --- response_body chop
 hello world!
 --- response_headers
-Apisix-Cache-Status: MISS
+Apisix-Cache-Status: EXPIRED