diff --git a/lib/fluent/plugin/out_http.rb b/lib/fluent/plugin/out_http.rb
index 09ab90858d..6fb972c3d3 100644
--- a/lib/fluent/plugin/out_http.rb
+++ b/lib/fluent/plugin/out_http.rb
@@ -37,7 +37,7 @@ class HTTPOutput < Output
 
     class RetryableResponse < StandardError; end
 
-    CacheEntry = Struct.new(:uri, :conn)
+    ConnectionCache = Struct.new(:uri, :conn)
 
     helpers :formatter
 
@@ -111,22 +111,21 @@ def initialize
       @proxy_uri = nil
       @formatter = nil
 
-      @cache = []
-      @cache_id_mutex = Mutex.new
+      @connection_cache = []
+      @connection_cache_id_mutex = Mutex.new
     end
 
     def close
       super
 
-      # Close all open connections
-      @cache.each {|entry| entry.conn.finish if entry.conn&.started? }
+      @connection_cache.each {|entry| entry.conn.finish if entry.conn&.started? }
     end
 
     def configure(conf)
       super
 
-      @cache = Array.new(actual_flush_thread_count, CacheEntry.new("", nil)) if @reuse_connections
-      @cache_id = 0
+      @connection_cache = Array.new(actual_flush_thread_count, ConnectionCache.new("", nil)) if @reuse_connections
+      @connection_cache_id = 0
 
       if @retryable_response_codes.nil?
         log.warn('Status code 503 is going to be removed from default `retryable_response_codes` from fluentd v2. Please add it by yourself if you wish')
@@ -322,23 +321,23 @@ def create_request(chunk, uri)
     def make_request_cached(uri, req)
       id = Thread.current.thread_variable_get(plugin_id)
       if id.nil?
-        @cache_id_mutex.synchronize {
-          id = @cache_id
-          @cache_id += 1
+        @connection_cache_id_mutex.synchronize {
+          id = @connection_cache_id
+          @connection_cache_id += 1
         }
         Thread.current.thread_variable_set(plugin_id, id)
       end
       uri_str = uri.to_s
-      if @cache[id].uri != uri_str
-        @cache[id].conn.finish if @cache[id].conn&.started?
+      if @connection_cache[id].uri != uri_str
+        @connection_cache[id].conn.finish if @connection_cache[id].conn&.started?
         http =  if @proxy_uri
                   Net::HTTP.start(uri.host, uri.port, @proxy_uri.host, @proxy_uri.port, @proxy_uri.user, @proxy_uri.password, @http_opt)
                 else
                   Net::HTTP.start(uri.host, uri.port, @http_opt)
                 end
-        @cache[id] = CacheEntry.new(uri_str, http)
+        @connection_cache[id] = ConnectionCache.new(uri_str, http)
       end
-      @cache[id].conn.request(req)
+      @connection_cache[id].conn.request(req)
     end
 
     def make_request(uri, req, &block)