HelloBug0 opened a new issue #3112: URL: https://github.com/apache/apisix/issues/3112
### Issue description When I study the code of APISIX, I'm not quite clear the file apisix/core/lrucache.lua from line 100 to line 134([here](https://github.com/apache/apisix/blob/966d68829add34d11695998af4e3035a0a473908/apisix/core/lrucache.lua#L100)) + What is the use of item_release? And I searched the project about this value(actually it's a function，right?), I couldn't find it. + Based on the last question, the value of item_release is nil, why should we call the function `fetch_valid_cache` twice in [line 100](https://github.com/apache/apisix/blob/966d68829add34d11695998af4e3035a0a473908/apisix/core/lrucache.lua#L100) and [line 119](https://github.com/apache/apisix/blob/966d68829add34d11695998af4e3035a0a473908/apisix/core/lrucache.lua#L119)? + Why do we need lock if we are using lru_cache which is process level cache? ### Environment * apisix version (master): * OS: (Linux VM-0-7-centos 3.10.0-1127.19.1.el7.x86_64 #1 SMP Tue Aug 25 17:23:54 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux) * OpenResty version: (nginx version: openresty/1.19.3.1 built by gcc 8.3.1 20190311 (Red Hat 8.3.1-3) (GCC) built with OpenSSL 1.1.1h 22 Sep 2020 TLS SNI support enabled configure arguments: --prefix=/usr/local/openresty/nginx --with-cc-opt='-O2 -DNGX_LUA_ABORT_AT_PANIC -I/usr/local/openresty/zlib/include -I/usr/local/openresty/pcre/include -I/usr/local/openresty/openssl111/include' --add-module=../ngx_devel_kit-0.3.1 --add-module=../echo-nginx-module-0.62 --add-module=../xss-nginx-module-0.06 --add-module=../ngx_coolkit-0.2 --add-module=../set-misc-nginx-module-0.32 --add-module=../form-input-nginx-module-0.12 --add-module=../encrypted-session-nginx-module-0.08 --add-module=../srcache-nginx-module-0.32 --add-module=../ngx_lua-0.10.19 --add-module=../ngx_lua_upstream-0.07 --add-module=../headers-more-nginx-module-0.33 --add-module=../array-var-nginx-module-0.05 --add-module=../memc-nginx-module-0.19 --add-module=../redis2-nginx-module-0.15 --add-module=../redis-nginx-module-0.3.7 --add-module=../ngx_stream_lua-0.0.9 --with-ld-opt='-Wl,-rpath,/usr/local/openresty/luajit/lib -L/usr/local/openresty/zlib/lib -L/usr/local/openresty/pcre/lib -L/usr/loca l/openresty/openssl111/lib -Wl,-rpath,/usr/local/openresty/zlib/lib:/usr/local/openresty/pcre/lib:/usr/local/openresty/openssl111/lib' --with-cc='ccache gcc -fdiagnostics-color=always' --with-pcre-jit --with-stream --with-stream_ssl_module --with-stream_ssl_preread_module --with-http_v2_module --without-mail_pop3_module --without-mail_imap_module --without-mail_smtp_module --with-http_stub_status_module --with-http_realip_module --with-http_addition_module --with-http_auth_request_module --with-http_secure_link_module --with-http_random_index_module --with-http_gzip_static_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gunzip_module --with-threads --with-compat --with-stream --with-http_ssl_module) ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
