FanOutSink makes a copy of Event, but the copy's attributes are unmodifiable

This makes it impossible to decorate an event after it has been copied.

My scenario:

node: collector.fanout
source: autoCollectorSource
sink: [logicalSink("collector.1"), logicalSink("collector.2")]

node: collector.1
source: autoCollectorSource
sink: diskFailover elasticSearchSink(...)

node: collector.2
source: autoCollectorSource
sink: diskFailover hiveSink(...)

—

The resulting exception which causes my downstream collector (which has the copied Event) to go down:

2011-08-04 20:11:12,519 ERROR com.cloudera.flume.core.connector.DirectDriver: Closing down due to exception during append calls
java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableMap.put(Collections.java:1301)
at com.cloudera.flume.core.EventBaseImpl.set(EventBaseImpl.java:65)
at com.cloudera.flume.handlers.rolling.RollSink.synchronousAppend(RollSink.java:231)
at com.cloudera.flume.handlers.rolling.RollSink$1.call(RollSink.java:183)
at com.cloudera.flume.handlers.rolling.RollSink$1.call(RollSink.java:181)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)