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Some time ago we have noticed a number of HTTP 408 in the nginx connections log. All such requests are POST requests with a request time equal to nginx client_body_timeout. We have gathered a tcp dump and decrypt tls traffic. It looks like the client starts a request, sends headers with specied non-zero content-length header but then after a delimeter between headers and a body there is no data transmitted at all from the client side. Nginx politely waits for any data and after a period equal to client_body_timeout gently closes the connection. Could anyone clarify what could be the cause of such behavior? Some additional information:

  • nginx version is 1.20.2 and the problem persists for a year or more.
  • The problem is sporadical. There is no dependence with daily load peaks but it looks like that some client's ip have such error more frequently that others.
  • Daily average number of HTTP 408 is ~1k per 110M of total POST requests.
  • The problem persists on different hosts, with different nginx instances and different services.
  • We tried to forward traffic through amazon alb but the problem persists.
  • The requests which lead to HTTP 408 are sent via firefox, chrome and our ios and android applications.
  • We cant reproduce the problem via tests even generating a large number of identical to client requests sent via jmeter.
  • The problem has very little impact on client's experience as we have no complains about these errors.
user2026706
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  • Same problem here, I am struggling with it for 2 years, for me this happens with 0.1% of users. It is always POST request and 408 with 0 size. Have you found the solution ? – Alpha and Omega Jul 22 '22 at 12:59
  • And I use php-fpm, do you have php behind POST processing ? – Alpha and Omega Jul 22 '22 at 13:07
  • @AlphaandOmega, no we haven't found any solution. We have considered this issue had no real impact on user's experience, so we have switched our focus on more critical tasks. However it would be great to solve this riddle. As for php-fpm - no. Nginx proxy passes requests to a java backend application. – user2026706 Jul 23 '22 at 13:14

1 Answers1

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We are having the same problem. In our case nginx server returns HTTP 408 code when receiving a HTTPS POST request with a large header (20 Kb) but 0 length body - the same request with smaller header works correctly. Adding just a 1 char body(' ') solved the problem in our case but I don't really understand the reason.

Mario Boss
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soosuke
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