About settimeouts doesn't work when i use read

[Roxanne63]

About settimeouts doesn't work when i use read

If I connect to the server but I don't send any data

The read API does not timeout and return timeout

I read the source code(resty.apisix.stream.xrpc.socket.lua) and found that it wait here at [coroutine._yield], but I did not find the location of the call to [coroutine.resume].
If we use [coroutine._yield] is required to use [coroutine.resume] back here, I wonder if my understanding is wrong

Reproduction code:

preread_by_lua_block {

local ffi = require("ffi")
local ffi_str = ffi.string
local xrpc_socket = require("resty.apisix.stream.xrpc.socket")

local downstream=xrpc_socket.downstream.socket()

downstream:settimeouts(3*1000, 3*1000, 3*1000)

ngx.log(ngx.ERR,"start read")
local data, err = downstream:read(5)

if not data then
	ngx.log(ngx.ERR,"read err:",err)
else
	local s = ffi.string(data, 5)
	ngx.log(ngx.ERR,"recv data:",data)
end

}

$ openresty -V
nginx version: openresty/1.21.4.1
built by gcc 4.8.5 20150623 (Red Hat 4.8.5-44) (GCC)
built with OpenSSL 1.1.1o 3 May 2022
TLS SNI support enabled
configure arguments: --prefix=/app/openresty/nginx --with-cc-opt='-O2 -DAPISIX_BASE_VER=latest -DNGX_GRPC_CLI_ENGINE_PATH=/app/openresty/libgrpc_engine.so -DNGX_HTTP_GRPC_CLI_ENGINE_PATH=/app/openresty/libgrpc_engine.so' --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-0.33 --add-module=../form-input-nginx-module-0.12 --add-module=../encrypted-session-nginx-module-0.09 --add-module=../srcache-nginx-module-0.32 --add-module=../ngx_lua-0.10.21 --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-0.3.9 --add-module=../ngx_stream_lua-0.0.11 --with-ld-opt='-Wl,-rpath,/app/openresty/luajit/lib -Wl,-rpath,' --add-module=/app/install/openresty-1.21.4.1/../mod_dubbo-master --add-module=/app/install/openresty-1.21.4.1/../ngx_multi_upstream_module-master --add-module=/app/install/openresty-1.21.4.1/../apisix-nginx-module-main --add-module=/app/install/openresty-1.21.4.1/../apisix-nginx-module-main/src/stream --add-module=/app/install/openresty-1.21.4.1/../apisix-nginx-module-main/src/meta --add-module=/app/install/openresty-1.21.4.1/../lua-var-nginx-module-master --add-module=/app/install/openresty-1.21.4.1/../grpc-client-nginx-module-main --with-poll_module --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-openssl=/app/install/openssl-1.1.1o --with-openssl-opt=-g --with-stream --with-http_ssl_module

[Roxanne63]

I used the source code(resty.apisix.stream.xrpc.socket.lua) to develop a program to interface to our devices,
This batch of devices is showing some connection to the server but not sending data.
The data transfer goes through the public network, tcp disconnected packets are filtered, I need the read API to have a timeout
So that I don't have multiple invalid connections on my server