fix(proxy-cache): follow request Cache-Control: no-cache header field

changelog/unreleased/kong/fix-proxy-cache-plugin-follow-no-cache-header.yml

@@ -0,0 +1,3 @@
+message: "**proxy-cache**: let cache action follow request `cache-control` header `no-cache` field base on rfc7234"
+type: bugfix
+scope: Plugin

kong/plugins/proxy-cache/handler.lua

@@ -97,8 +97,7 @@ local function cacheable_request(conf, cc)
   end
 
   -- check for explicit disallow directives
-  -- TODO note that no-cache isnt quite accurate here
-  if conf.cache_control and (cc["no-store"] or cc["no-cache"] or
+  if conf.cache_control and (cc["no-store"] or
      ngx.var.authorization) then
     return false
   end
@@ -260,15 +259,22 @@ function ProxyCacheHandler:access(conf)
     return
   end
 
+  local ctx = kong.ctx.plugin
+
   set_header(conf, "X-Cache-Key", cache_key)
+  if conf.cache_control then
+    if cc["no-cache"] then
+      return signal_cache_req(ctx, conf, cache_key, "Bypass")
+    end
+  end
+
 
   -- try to fetch the cached object from the computed cache key
   local strategy = require(STRATEGY_PATH)({
     strategy_name = conf.strategy,
     strategy_opts = conf[conf.strategy],
   })
 
-  local ctx = kong.ctx.plugin
   local res, err = strategy:fetch(cache_key)
   if err == "request object not in cache" then -- TODO make this a utils enum err
 

spec/03-plugins/31-proxy-cache/02-access_spec.lua

@@ -595,6 +595,7 @@ do
 
       assert.res_status(200, res)
       assert.same("Miss", res.headers["X-Cache-Status"])
+
       --local cache_key = res.headers["X-Cache-Key"]
 
       -- wait until the underlying strategy converges
@@ -611,6 +612,17 @@ do
       assert.res_status(200, res)
       assert.same("Hit", res.headers["X-Cache-Status"])
 
+      local res = assert(client:get("/cache/2", {
+        headers = {
+          host = "route-7.test",
+          ["Cache-Control"] = "no-cache",
+        }
+      }))
+
+      assert.res_status(200, res)
+      assert.same("Bypass", res.headers["X-Cache-Status"])
+      assert.is_not_nil(res.headers["X-Cache-Key"])
+
       -- if strategy is local, it's enough to simply use a sleep
       if strategies.LOCAL_DATA_STRATEGIES[policy] then
         ngx.sleep(3)