(2.14) alarms: modify logback encoding to show actual alarm type

Motivation:

Logback pattern encoding allows for the display of marker names
using either '%marker' or '%markerSimpleName'.  The way Alarms currently
uses markers, however, is to chain the actual value of a sub-marker as
another sub-marker.

The current encoding thus merely displays the marker names, which is
not all that informative (and perhaps even annoying): e.g.,

17 Nov 2015 07:07:17 ALARM [ ALARM_TYPE ] (fndca3a.fnal.gov)(user-command)(<na>) This is a test alarm for OutOfMemory error reporting.

Modification:

Upon arrival of the event at the server, during the preprocessing of
the alarm for either email or the optional history file, the submarker
is accessed and added to the event's MDC property map.  The pattern
encoding is changed to display the new MDC property instead of the marker.

Result:

A more meaningful printout, e.g.,

17 Nov 2015 07:07:17 FATAL_JVM_ERROR (fndca3a.fnal.gov)(user-command)(<na>) This is a test alarm for OutOfMemory error reporting.

Target: 2.14
Require-book: no
Require-notes: yes
Acked-by: Gerd
Patch: https://rb.dcache.org/r/8781/

modules/dcache/src/main/java/org/dcache/alarms/logback/LogEntryHandler.java

@@ -74,13 +74,16 @@ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 import com.google.common.base.Strings;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.slf4j.Marker;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.util.Iterator;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import org.dcache.alarms.AlarmMarkerFactory;
 import org.dcache.alarms.AlarmPriority;
 import org.dcache.alarms.AlarmPriorityMap;
 import org.dcache.alarms.dao.LogEntry;
@@ -98,6 +101,8 @@ public class LogEntryHandler {
     private static final Logger LOGGER
         = LoggerFactory.getLogger(LogEntryHandler.class);
 
+    private static final String MDC_TYPE = "type";
+
     /**
      * Future runnable worker task.
      */
@@ -122,6 +127,7 @@ public void run() {
                  * service itself.
                  */
                 if (historyEnabled && priority >= historyThreshold.ordinal()) {
+                    setType(event);
                     historyAppender.doAppend(event);
                 }
 
@@ -130,6 +136,7 @@ public void run() {
                  * email.
                  */
                 if (emailEnabled && priority >= emailThreshold.ordinal()) {
+                    setType(event);
                     emailAppender.doAppend(event);
                 }
 
@@ -360,6 +367,19 @@ public void handle(ILoggingEvent eventObject) {
         executor.execute(new LogEntryTask(eventObject));
     }
 
+    private void setType(ILoggingEvent eventObject) {
+        if (eventObject.getMDCPropertyMap().containsKey(MDC_TYPE)) {
+            return;
+        }
+
+        Marker sub = AlarmMarkerFactory.getTypeSubmarker(eventObject.getMarker());
+        Iterator<Marker> it = sub.iterator();
+        if (it.hasNext()) {
+            String type = it.next().getName();
+            eventObject.getMDCPropertyMap().put(MDC_TYPE, type);
+        }
+    }
+
     private void startEmailAppender() {
         LoggerContext context
             = (LoggerContext) LoggerFactory.getILoggerFactory();

skel/share/defaults/alarms.properties

@@ -165,15 +165,15 @@ alarms.email.buffer-size=1
 
 #  ---- Pattern to use to encode email alert.
 #
-alarms.email.encoding-pattern=%d{dd MMM yyyy HH:mm:ss} %marker \\(%X{host}\\)\\(%X{service}\\)\\(%X{domain}\\) %m%n
+alarms.email.encoding-pattern=%d{dd MMM yyyy HH:mm:ss} %X{type} \\(%X{host}\\)\\(%X{service}\\)\\(%X{domain}\\) %m%n
 
 #  ---- Level of priority serving as threshold for logging history entry.
 #       All alerts at this level or above are logged to the history file.
 (one-of?critical|high|medium|low)alarms.history.threshold=critical
 
 #  ---- Pattern to use to encode history log entry.
 #
-alarms.history.encoding-pattern=%d{dd MMM yyyy HH:mm:ss} %marker \\(%X{host}\\)\\(%X{service}\\)\\(%X{domain}\\) %m%n
+alarms.history.encoding-pattern=%d{dd MMM yyyy HH:mm:ss} %X{type} \\(%X{host}\\)\\(%X{service}\\)\\(%X{domain}\\) %m%n
 
 #  ---- Path of history log file
 #