I'm not sure if I should be commenting directly in JIRA (or how to get an account), but I submitted a pull request for this: https://github.com/qos-ch/logback/pull/339

The MDC is not available when writing the access log. The MDC variables are removed by the filter (post-processing) running way before the access log.

I don't quite understand because my PR worked when I pulled it into my dropwizard project, and access logs included the values I inserted in the MDC at the beginning of the request. Thanks, Paul On Mon, Nov 7, 2016 at 1:24 AM, Erik Lund Jensen (JIRA) <noreply-jira@qos.ch

wrote:

Erik Lund Jensen <http://jira.qos.ch/secure/ViewProfile.jspa?name=ErikLundJensen> *commented* on [image: New Feature] LOGBACK-1016 <http://jira.qos.ch/browse/LOGBACK-1016>

Re: logback-access: Enable MDC support <http://jira.qos.ch/browse/LOGBACK-1016>

The MDC is not available when writing the access log. The MDC variables are removed by the filter (post-processing) running way before the access log.It is not a solution just to not remove the MDC variables, as you wouldn't want the MDC variables to stay around for the next request.

In stead you may write a few classes for handling this.First, write a class for holding your variables. For example:

public class AccessLogger { private static ThreadLocal<AdditionalInfo> currentInfo = new ThreadLocal<>();

public static String getAndRemoveAdditionalInfo() { AdditionalInfo additionalInfo = currentInfo.get(); currentInfo.remove(); return additionalInfo.getInfo(); } public static void setAdditionalInfo(String info){ currentInfo.set(new AdditionalInfo(info)); } public static final class AdditionalInfo { private String info; public AdditionalInfo(String info) { super(); this.info = info; } public String getInfo() { return info; } } }

Secondly, use that class in a custom access converter:

public class AdditionalInfoConverter extends AccessConverter { @Override public String convert(IAccessEvent event) { String info = AccessLogger.getAndRemoveAdditionalInfo(); return info!=null ? info : "-"; } }

Thirdly, add the customer converter to a new wrapper class. This class adds %X to get the additional info.It would be nice if Logback supported a callback to extend PatterLayout, however, this is how it can be done without changing the Logback source code.

public class AccessLogLayoutWrapper extends PatternLayoutEncoderBase<IAccessEvent> { @Override public void start() { PatternLayout patternLayout = new PatternLayout(); patternLayout.getDefaultConverterMap().put("X", AdditionalInfoConverter.class.getName()); patternLayout.setContext(context); patternLayout.setPattern(getPattern()); patternLayout.start(); this.layout = patternLayout; super.start(); } }

Finally, use some filter to set the additional info in AccessLogger. ... AccessLogger.setAdditionalInfo( userName); [image: Add Comment] <http://jira.qos.ch/browse/LOGBACK-1016#add-comment> Add Comment <http://jira.qos.ch/browse/LOGBACK-1016#add-comment>

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