Nginx upstream timed out (110: Connection timed out)

More logs in nginx

2021/07/08 10:54:31 [error] 570#570: *169 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 100.19.76.187, server: _, request: “POST /message-bus/4cf07f106ff14fd885fd735ea28abce4/poll?dlp=t HTTP/2.0”, upstream: “http://127.0.0.1:3000/message-bus/4cf07f106ff14fd885fd735ea28abce4/poll?dlp=t”, host: “1o24bbs.com”, referrer: “求ICC的群 - CS News - 1024 BBS

2021/07/08 10:54:32 [error] 570#570: *169 upstream timed out (110: Connection timed out) while connecting to upstream, client: 100.19.76.187, server: _, request: “POST /message-bus/fe81f75495324a109de3812a3c5a9abd/poll?dlp=t HTTP/2.0”, upstream: “http://127.0.0.1:3000/message-bus/fe81f75495324a109de3812a3c5a9abd/poll?dlp=t”, host: “1o24bbs.com”, referrer: “求去哪家ICC的建议 - CS News - 1024 BBS

2021/07/08 10:54:33 [error] 570#570: *169 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 100.19.76.187, server: _, request: “POST /message-bus/1dd105462c5b4b4c978e1702fa885e14/poll?dlp=t HTTP/2.0”, upstream: “http://127.0.0.1:3000/message-bus/1dd105462c5b4b4c978e1702fa885e14/poll?dlp=t”, host: “1o24bbs.com”, referrer: “谈谈自己的找工作和icc经历 - CS News - 1024 BBS

2021/07/08 10:54:36 [error] 570#570: *13261 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 220.196.56.24, server: _, request: “GET /?374e828961d36d46bd99dc8e13b7f640 HTTP/1.1”, upstream: “http://127.0.0.1:3000/?374e828961d36d46bd99dc8e13b7f640”, host: “1o24bbs.com”, referrer: “https://gateway.zscalertwo.net:443/auT?origurl=https%3A%2F%2F1o24bbs.com%2F%3F374e828961d36d46bd99dc8e13b7f640&wexps=1&_ordtok=SWk3WVhmhHBPJ4rLFk4nDRnkZ3&wexps=1