Use same description for same meter name in Log4j2Metrics (#4864)

Avoids having different descriptions for the same meter name as this causes issues with some integrations that expect one description for all.

Author: izeye

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/logging/Log4j2Metrics.java

@@ -51,6 +51,8 @@ public class Log4j2Metrics implements MeterBinder, AutoCloseable {
 
     private static final String METER_NAME = "log4j2.events";
 
+    private static final String METER_DESCRIPTION = "Number of log events";
+
     private final Iterable<Tag> tags;
 
     private final LoggerContext loggerContext;
@@ -156,42 +158,42 @@ class MetricsFilter extends AbstractFilter {
             fatalCounter = Counter.builder(METER_NAME)
                 .tags(tags)
                 .tags("level", "fatal")
-                .description("Number of fatal level log events")
+                .description(METER_DESCRIPTION)
                 .baseUnit(BaseUnits.EVENTS)
                 .register(registry);
 
             errorCounter = Counter.builder(METER_NAME)
                 .tags(tags)
                 .tags("level", "error")
-                .description("Number of error level log events")
+                .description(METER_DESCRIPTION)
                 .baseUnit(BaseUnits.EVENTS)
                 .register(registry);
 
             warnCounter = Counter.builder(METER_NAME)
                 .tags(tags)
                 .tags("level", "warn")
-                .description("Number of warn level log events")
+                .description(METER_DESCRIPTION)
                 .baseUnit(BaseUnits.EVENTS)
                 .register(registry);
 
             infoCounter = Counter.builder(METER_NAME)
                 .tags(tags)
                 .tags("level", "info")
-                .description("Number of info level log events")
+                .description(METER_DESCRIPTION)
                 .baseUnit(BaseUnits.EVENTS)
                 .register(registry);
 
             debugCounter = Counter.builder(METER_NAME)
                 .tags(tags)
                 .tags("level", "debug")
-                .description("Number of debug level log events")
+                .description(METER_DESCRIPTION)
                 .baseUnit(BaseUnits.EVENTS)
                 .register(registry);
 
             traceCounter = Counter.builder(METER_NAME)
                 .tags(tags)
                 .tags("level", "trace")
-                .description("Number of trace level log events")
+                .description(METER_DESCRIPTION)
                 .baseUnit(BaseUnits.EVENTS)
                 .register(registry);
         }