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Why do I see a Log Split within the Loadmaster L7 Debug Trace Logs

 

Information

 

Summary:

When using content rule with the L7 Debug Trace enabled a log spit can be observed

when the loadmaster logs the use of a Host header in the request.

Environment:

Product: Loadmaster

Version: 7.2.56.0

Platform: Hardware

Application: any

Question/Problem Description:

Why am I seeing a Log Split in the L7 Debug Trace?

' HTTP/1.1

2022-04-30T12:00:00+00:00 LMhostname kernel: Host'

Can you explain the meaning behind the log split?

Is this log split a bug?

Steps to Reproduce:

Use content rules with a modify URL rule enabled.

Enable the L7 Debug trace:

System Configuration --> Logging Options --> System Log Files --> Debug Options -->

Enable L7 Debug Trace --> Enable Trace

 

PLEASE NOTE: The "L7 Debug Trace" should only be used for the purposes of troubleshooting and should be disabled immediately afterwards. This is because the "L7 Debug Trace" is a verbose for of debug logging that can consume a lot of resources on the device quickly which can ultimately impact overall performance of the Loadmaster.

Error Message:
2022-04-30T12:00:00+00:00 LMhostname kernel: L7: ffff88882e347cd0: l7_mangle_urireplace '/kemp/test/?id=865143' '/progress-kemp/test/?id=865143' ' HTTP/1.1 
2022-04-30T12:00:00+00:00 LMhostname kernel: Host'
Defect Number: LM-1055
Enhancement Number: LM-1278
Cause: For the specific log message mentioned (kernel: Host'), it can happen that under certain circumstances, one of the three strings logged will contain a newline or CRLF sequence and wrap to a second line.
Resolution:

HTTP/1.1 - Feature Description

By default, the LoadMaster uses HTTP/1.0. However you may opt to use HTTP/1.1 which will operate more efficiently.
When using HTTP/1.1, the health checks are multiplexed to a single connection.
This means that more health checks are sent to the server in a single connection which is more efficient from a connection point of view,
that is, there is only one connection rather than multiple connections.

This affect Loadmaster to real server connections.

 

HTTP/1.1 Host - Feature Description

This field will only be visible if 'Use HTTP/1.1' is selected under the real server health check options.

When using HTTP/1.1 checking, the Real Servers require a hostname to be supplied in each request. If no value is set, then this value is the IP address of the Virtual Service.

 

'HTTP/1.1 Host' - L7 Debug Log

For the specific log message mentioned (kernel: Host'), it can happen that under certain circumstances, one of the three strings logged will contain a newline or CRLF sequence and wrap to a second line.

2022-04-30T12:00:00+00:00 LMhostname kernel: L7: ffff88882e347cd0: l7_mangle_urireplace '/kemp/test/?id=865143' '/progress-kemp/test/?id=865143' ' HTTP/1.1 
2022-04-30T12:00:00+00:00 LMhostname kernel: Host'

String 1: '/kemp/test/?id=865143'

String 2: '/progress-kemp/test/?id=865143'

String 3: ' HTTP/1.1 Host'

 

This has been recognized as a issue and is being worked under the enhancement ID: LM-1278

Please referrer to the LoadMaster firmware release notes for specific versions of LoadMaster OS in order to verify if the fix has been included.

LoadMaster firmware release notes can be accessed here.

 

NOTE: Generally speaking we would discourage any non-troubleshooting processing of debug logs
as the messages themselves are subject to change (or may even be removed) from firmware release to firmware release as a result of the custom nature of the logging.

Workaround:  
Notes:

Web User Interface Feature Description

LoadMaster firmware release notes


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