RM has a bunch of metrics that we may want to write into the timeline backend to. I attached the metrics.json that I've crawled via http://localhost:8088/jmx?qry=Hadoop:*. IMHO, we need to pay attention to three groups of metrics:
The problem is that unlike other metrics belongs to a single application, these ones belongs to RM or cluster-wide. Therefore, current write path is not going to work for these metrics because they don't have the associated user/flow/app context info. We need to rethink of modeling cross-app metrics and the api to handle them.