[middleman] failed to keepalive to <host> connection in dubious state

[Nithya95]

Hi Team,
I'm getting 502 Bad Gateway from middleman with below error for few calls while doing concurrent testing with 100+ request. Increased keep-alive time to 300s and lua_socket_pool_Size to 60 and still same error exists. While the upstream connection sends the response with proper response body.

The issue is when sending large concurrent request, previous connection is not properly closed and unread data still present in buffer. Can anybody give insight on proceeding this issue?

2020/07/20 14:22:15 [error] 167#0: *1153003 [lua] access.lua:102: execute(): [middleman] failed to keepalive to :443: connection in dubious state, client: , server: kong, request: "GET /xyz HTTP/1.1", host: "", referrer: "https://xyz"

[thameema]

Nithya - If you get 502 Bad Gateway that tells me that the downstream system is unable to handle the requests and appears to be unavailable Kong. Try to see whether the downstream application is able to handle the connections. To test it out replace the downstream application with a mock server that just records the request and responds and see whether this issue is going away.