public long estimateHeapUsage() {
      return message.length + BASE_USAGE;
    }
Completely non-scientific estimate of how much one of these objects takes, along with the
LinkedList overhead. This doesn't need to be exact, since we don't expect a ton of these
alerts.
hbase-server/src/main/java/org/apache/hadoop/hbase/monitoring/MemoryBoundedLogMessageBuffer.java