SPWebConfigModification - Features over writing each other modification - sharepoint-2010

Question

I am using log4Net with share point 2010. I have a feature which automatically adds the log4net config when my soultion is deployed in Error mode using following code
SPWebService service = SPWebService.ContentService;
service.WebConfigModifications.Clear();
//ADD log4Net config section
service.WebConfigModifications.Add(new SPWebConfigModification()
{
Path = "configuration/configSections",
Name = "section[#name='log4net']",
Sequence = 0,
Owner = CREATE_NAME,
Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode,
Value = string.Format(#"<section name='log4net' type='log4net.Config.Log4NetConfigurationSectionHandler, log4net, Version={0}, Culture=neutral, PublicKeyToken={1}' />", LOG4NET_VERSION, LOG4NET_PUBLIC_KEY_TOKEN)
});
string log4netConfig = #"<log4net>
<appender name='RollingFileAppender' type='log4net.Appender.RollingFileAppender'>
<file value='C:\\logs\\Logger.log' />
<appendToFile value='true' />
<rollingStyle value='Composite' />
<datePattern value='yyyyMMdd' />
<maxSizeRollBackups value='200' />
<maximumFileSize value='50MB' />
<layout type='log4net.Layout.PatternLayout'>
<conversionPattern value='%d [%t] %-5p %c [%x] <%X{auth}> - %m%n' />
</layout>
</appender>
<root>
<level value='ERROR' />
<appender-ref ref='RollingFileAppender' />
</root>
</log4net>";
//add error default config
service.WebConfigModifications.Add(new SPWebConfigModification()
{
Path = "configuration",
Name = "log4net",
Sequence = 0,
Owner = CREATE_NAME,
Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode,
Value = log4netConfig
});
service.Update();
service.ApplyWebConfigModifications();
I wanted to create another feature which over writes Error mode of the log4net and change it to debug, so that the end user does not have to modifiy web config manually.
The problem is when the second feature is activated, it deletes everything added by the first feature.
Is this standard behaviour ?? Any feature that would activate would delete the changes by other feature.
EDIT 2
Steps to replicate
Create 2 feature. both of them should add some different entries in web config.
Activate feature 1 - Feature 1 changes are in web config
Activate feature 2 - Feature 2 changes are in web config but feature 1
changes are gone
Deactivate both the features
Activate feature 2 - Feature 2 changes are in web config
Activate feature 1 - Feature 1 changes are in web config but feature
2 changes are gone

Answer 1

The reason why the first web configuration is removed is because of the code block:
service.WebConfigModifications.Clear();
Basically you're saying that you will be clearing all other configurations set in your web config prior to adding the items in your feature. Removing the said code block should fix your issue.
If you need to do some other things when activating or deactivating a feature try using Feature Receivers. A good example to start with web configurations and feature receivers can be found here.
Also to give you more idea on the code block above is giving you problems you can check out the problem another guy which had the similar problem here.

Answer 2

if I understand this correctly, what's happening is you add a webconfigmodification, this isn't technically "added" yet as it is hasn't been implemented just yet. When you created the 2nd modification, it overwrites the first modification you created, which in turns, erases the first modification that was made, and this was the one that was applied.