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/* Changing the layout to use less space for mobiles */
@media screen and (max-device-width: 480px), screen and (-webkit-min-device-pixel-ratio: 2) {
    #email-body { min-width: 30em !important; }
    #email-page { padding: 8px !important; }
    #email-banner { padding: 8px 8px 0 8px !important; }
    #email-avatar { margin: 1px 8px 8px 0 !important; padding: 0 !important; }
    #email-fields { padding: 0 8px 8px 8px !important; }
    #email-gutter { width: 0 !important; }
}
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<div id="email-body">
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                                    <a class="user-hover" rel="cemo" id="email_cemo" href="http://jira.qos.ch/secure/ViewProfile.jspa?name=cemo" style="color:#326ca6;">cemalettin koc</a>
     created <img src="http://jira.qos.ch/images/icons/issuetypes/bug.png" height="16" width="16" border="0" align="absmiddle" alt="Bug"> <a style='color:#326ca6;text-decoration:none;' href='http://jira.qos.ch/browse/LOGBACK-1057'>LOGBACK-1057</a>
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                <a style='color:#326ca6;text-decoration:none;' href='http://jira.qos.ch/browse/LOGBACK-1057'><strong>Modifing MDCPropertyMap of LoggingEvents </strong></a>
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        <strong style="font-weight:normal;color:#505050;">Issue Type:</strong>
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                <img src="http://jira.qos.ch/images/icons/issuetypes/bug.png" height="16" width="16" border="0" align="absmiddle" alt="Bug">        Bug
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        <strong style="font-weight:normal;color:#505050;">Assignee:</strong>
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                                        <a class="user-hover" rel="logback-dev@qos.ch" id="email_logback-dev@qos.ch" href="http://jira.qos.ch/secure/ViewProfile.jspa?name=logback-dev%40qos.ch" style="color:#326ca6;">Logback dev list</a>
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        <strong style="font-weight:normal;color:#505050;">Created:</strong>
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    <td style="color:#000000;font-family:Arial,FreeSans,Helvetica,sans-serif;font-size:12px;padding:0 0 10px 0;width:100%;">
        09/Mar/15 4:12 PM
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        <strong style="font-weight:normal;color:#505050;">Description:</strong>
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        <p style='margin-top:0;margin-bottom:10px;'>I have a layout which is generating JSON from logging events and MDC Context. MDC is great and I want to add parameters to MDC Context conditionally. For example, I would like add request information as JSON into MDC conditionally on Error Level log entries. I am not familiar with Logback internals but gave a try with Logback Filter implementation. I have used:</p>

<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">

   <span class="code-keyword">public</span> FilterReply decide(ILoggingEvent event) {

      <span class="code-comment">// simplified <span class="code-keyword">for</span> demo
</span>      <span class="code-comment">// conditionally I am putting some attributes here
</span>      Map<<span class="code-object">String</span>, <span class="code-object">String</span>> mdcPropertyMap = event.getMDCPropertyMap();
      <span class="code-keyword">if</span> (event.getLevel().isGreaterOrEqual(Level.ERROR)) {
         mdcPropertyMap.put(<span class="code-quote">"demo"</span>, <span class="code-quote">"demo"</span>);
      }
      <span class="code-keyword">return</span> FilterReply.ACCEPT;
   }

</pre>
</div></div>

<p style='margin-top:0;margin-bottom:10px;'>I am expecting mdcPropertyMap to be cleared for each event but it does not. LoggingEvent has a internal CACHED_NULL_MAP map and its modified per touch.</p>

<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">
  <span class="code-keyword">private</span> <span class="code-keyword">static</span> <span class="code-keyword">final</span> Map<<span class="code-object">String</span>, <span class="code-object">String</span>> CACHED_NULL_MAP = <span class="code-keyword">new</span> HashMap<<span class="code-object">String</span>, <span class="code-object">String</span>>();
</pre>
</div></div>

<p style='margin-top:0;margin-bottom:10px;'>I could not be sure but it seems a little bid buggy to me. Can someone verify this behaviour?</p>

<p style='margin-top:0;margin-bottom:10px;'>For those who are interested why I am not using MDC.put in a Servlet Filter implementation because I am conditionally adding some attributes. Serialising HttpRequest into JSON is not cheap task but having Http Request information is giving great insights about error. Using Filter is the only way I found to add conditionally attributes so far. What I would like to use is: </p>

<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">
   <span class="code-keyword">public</span> FilterReply decide(ILoggingEvent event) {
      <span class="code-keyword">if</span> (event.getLevel().isGreaterOrEqual(Level.WARN)) {
         MDC.put(<span class="code-quote">"demo"</span>, <span class="code-quote">"demo"</span>);
      }
      <span class="code-keyword">return</span> FilterReply.ACCEPT;
   }
</pre>
</div></div>




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        <strong style="font-weight:normal;color:#505050;">Project:</strong>
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        <a style="color:#326ca6;" href="http://jira.qos.ch/browse/LOGBACK">logback</a>
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        <strong style="font-weight:normal;color:#505050;">Priority:</strong>
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                        <img src="http://jira.qos.ch/images/icons/priorities/major.png" height="16" width="16" border="0" align="absmiddle" alt="Major">                Major
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        <strong style="font-weight:normal;color:#505050;">Reporter:</strong>
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                                        <a class="user-hover" rel="cemo" id="email_cemo" href="http://jira.qos.ch/secure/ViewProfile.jspa?name=cemo" style="color:#326ca6;">cemalettin koc</a>
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