在Apache Storm中运行时编辑螺栓过程

Question

My project streams object data through storm to a graphics application. The appearance of these objects depends upon variables assigned by a bolt in the storm topology.

My question is whether it is possible to update the bolt process by sending a message to it that changes the variables it attaches to object data. For example, after sending a message to the bolt declaring that I want any object with parameter x above a certain number to appear as red rather than blue. The bolt process would then append a red rgb variable to the object data rather than blue.

I was thinking this would be possible by having a displayConfig class that the bolt uses to apply appearance and who's contents can be edited by messages with a certain header.

Is this possible?

Answer 1

It is possible, but you need to do it manually and prepare you topology before you start it.

There are two ways to do this:

1. use a local config file for bolt that you put into the worker machine (maybe via NFS). The bolts regularly check the file for updates an read an updated configuration if you do change the file.

2. You use one more spout that produces a configuration stream. All bolts you want to send a configuration during runtime, need to consumer from this configuration-spout via "allGrouping". When processing input tuple, you check if its a regular data tuple or and configuration tuple (and update you config accordingly).