On 25/05/2023 09:14, Paul Baines wrote:
Hello! We upgraded a Windows Tomcat instance from 8.5.41 to 8.5.84. This Tomcat instance is behind a load balancer. Since the upgrade the Tomcat access log (AccessLogValve) has an "empty" entry with response 400 for every TCP half-open health check from the load balancer. Because the health check is every 5 seconds from redundant load-balancers we are getting quite alot of junk in the access log. The TCP half-open check is:LB --> SYN --> Tomcat 443LB <-- SYN/ACK <-- Tomcat 443LB --> FIN --> Tomcat 443LB <-- FIN/ACK <-- Tomcat 443Access log excerpt:[03/May/2023:00:13:58 +0200] 10.20.10.2 - "-" - "-" "-" 400 0 - -[03/May/2023:00:13:59 +0200] 10.20.10.3 - "-" - "-" "-" 400 0 - -[03/May/2023:00:14:03 +0200] 10.20.10.2 - "-" - "-" "-" 400 0 - -[03/May/2023:00:14:04 +0200] 10.20.10.3 - "-" - "-" "-" 400 0 - -[03/May/2023:00:14:08 +0200] 10.20.10.2 - "-" - "-" "-" 400 0 - -[03/May/2023:00:14:09 +0200] 10.20.10.3 - "-" - "-" "-" 400 0 - -[03/May/2023:00:14:13 +0200] 10.20.10.2 - "-" - "-" "-" 400 0 - - We can reproduce this effect from Windows Powershell with:Test-NetConnection -ComputerName tomcat.server.name -RemotePort 443 My question is, is this expected behaviour?
Yes.
Is TCP half-open health check supported by Tomcat?
Yes. But you are going to see 400 responses in the logs for each empty request.
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