Usage of prefix with LogstashEncoder and LayoutWrappingEncoder throws errors

[nhakimjee]

I am trying to send my application logs to syslog using LogstashTcpSocketAppender. My configuration is as follows:

127.0.0.1:514 30 second 5 minutes 16384

  <!-- encoder is required -->
  <encoder class="net.logstash.logback.encoder.LogstashEncoder">
  	 <prefix class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
        <layout class="ch.qos.logback.classic.PatternLayout">
           <pattern>%syslogStart{LOCAL0}</pattern>
        </layout>
     </prefix>

    <fieldNames>
	  <thread>[ignore]</thread>
	  <levelValue>[ignore]</levelValue>
</fieldNames>

    <includeCallerData>true</includeCallerData>      
  </encoder>
  
  <includeCallerData>true</includeCallerData>

However, I get the following errors when I startup my web application.
09:21:48,936 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Found resource [logback-test.xml] at [file:/home/nhakimjee/work/Workspaces/syslog/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/bap/WEB-INF/classes/logback-test.xml]
09:21:49,001 |-INFO in ch.qos.logback.classic.joran.action.ConfigurationAction - debug attribute not set
09:21:49,002 |-INFO in ch.qos.logback.core.joran.action.ConversionRuleAction - registering conversion word syslogStart with class [ch.qos.logback.classic.pattern.SyslogStartConverter]
09:21:49,002 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - About to instantiate appender of type [net.logstash.logback.appender.LogstashTcpSocketAppender]
09:21:49,028 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - Naming appender as [stash-tcp]
09:21:49,358 |-ERROR in ch.qos.logback.core.joran.util.PropertySetter@5475d1b2 - A "net.logstash.logback.encoder.LogstashEncoder" object is not assignable to a "ch.qos.logback.core.Appender" variable.
09:21:49,358 |-ERROR in ch.qos.logback.core.joran.util.PropertySetter@5475d1b2 - The class "ch.qos.logback.core.Appender" was loaded by
09:21:49,359 |-ERROR in ch.qos.logback.core.joran.util.PropertySetter@5475d1b2 - [WebappClassLoader
context: ROOT
delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@2f92e0f4
] whereas object of type
09:21:49,359 |-ERROR in ch.qos.logback.core.joran.util.PropertySetter@5475d1b2 - "net.logstash.logback.encoder.LogstashEncoder" was loaded by [WebappClassLoader
context: ROOT
delegate: false
----------> Parent Classloader:
java.net.URLClassLoader@2f92e0f4
].
09:21:49,359 |-INFO in ch.qos.logback.core.joran.action.NestedComplexPropertyIA - Assuming default type [net.logstash.logback.fieldnames.LogstashFieldNames] for [fieldNames] property

I used the examples to for the above configuration, am I missing some something?

Thanks,

Nuruddin

[philsttr]

Hi Nuruddin,

Can you please provide your complete logback.xml file (while masking any sensitive data)? Specifically, I need to see the appender element.

[nhakimjee]

Sorry for the delay. Here is my appender:

<conversionRule conversionWord="syslogStart" converterClass="ch.qos.logback.classic.pattern.SyslogStartConverter"/>

<appender name="stash-tcp" class="net.logstash.logback.appender.LogstashTcpSocketAppender">
  <!-- Multiple destinations can be set and a reconnection strategy can be introduced -->
  <destination>127.0.0.1:514</destination>
  <reconnectionDelay>30 second</reconnectionDelay>
  <keepAliveDuration>5 minutes</keepAliveDuration>
  <writeBufferSize>16384</writeBufferSize>

  <!-- encoder is required -->
  <encoder class="net.logstash.logback.encoder.LogstashEncoder">
  	<prefix class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
      <layout class="ch.qos.logback.classic.PatternLayout">
        <pattern>%syslogStart{LOCAL6}</pattern>
      </layout>
    </prefix>

    <fieldNames>
	  <thread>[ignore]</thread>
	  <levelValue>[ignore]</levelValue>
    </fieldNames>

    <includeCallerData>true</includeCallerData>      
  </encoder>
  
  <includeCallerData>true</includeCallerData>
</appender>

[philsttr]

Looks like this is caused by a backwards incompatible change introduced in logback 1.2.1. Specifically, this change

For now, you can workaround this by using logback prior to 1.2.1.

I tested your config using logback 1.2.0 and 1.1.7, and it worked in both cases.

[philsttr]

Submitted LOGBACK-1326 with qos-ch/logback#383 to hopefully fix this in logback.

[nhakimjee]

Thank you!

[imod]

this does not look to be resolved in any foreseeable time - is there any other way this could be fixed?

[philsttr]

According to this comment, @ceki has marked LOGBACK-1326 to be fixed in logback 1.3.0-alpha5. And it looks like he has been active recently in the logback repo, so hopefully, this will be addressed soon. I know 2 years is a long time to wait for a PR to be merged, but I'm still hopeful due to the recent activity.

Without the requested change in logback, the only workaround would be to copy the LayoutWrappingEncoder class from logback, and make the change from the PR Specifically, change the type of the parent field and setParent method parameter to ContextAware. Then use the modified class instead of LayoutWrappingEncoder from logback.

[philsttr]

LOGBACK-1326 has been fixed in logback 1.2.5