They are the streamIds for the streams that the bolt is emitting to. http://storm.apache.org/javadoc/apidocs/backtype/storm/topology/InputDeclarer.html
If you do not specify a stream to emit to, you will be using default. "__system" is a storm internal stream. On Wed, Jul 22, 2015 at 11:45 AM Hong Jeon <[email protected]> wrote: > Hi, > > Every "topology.builtin.metrics.bucket.size.secs," each component in my > topology is sending builtin metrics to a metrics consumer (as expected). > However, I am confused about some of the data that I am receiving. > > For example, one DataPoint object I receive has a name of "__emit-count" > and a value (map) of {"default" : 980, "__system": 20}. > > How do I figure out what the meaning of "__system" key is? or even the > meaning of "default" key. > > > > >
