Score:1

AWS ALB and HAProxy Keep-Alive header

in flag

Has any one come across this behavior?

  • AWS ALB is sending traffic to HaProxy.
  • HaProxy sets keep-alive header to 29 seconds.
  • Client connected to ALB does not see this header.
  • It can only see "Connection: keep-alive" header.
  • Basically, ALB is stripping out keep-alive header.
  • Enabling/Disabling HTTP/2.0 in ALB settings has no effect on this behavior.
  • ALB idle connection timeout is more than 29 seconds.
  • Occasionally client gets 502 error from ALB possibly because ALB tries to use a connection just before 29s window is over and HAProxy closes it in few milliseconds meaning that connection was idle for last 29 seconds.
  • Is setting keep-alive timeout > ALB idle timeout the only solution here? Why would ALB not try to open a new connection if it receives a connection reset in this race condition?
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