So Logan has a viable “Application Configuration Application” (ACA). I’m reminded that I should never be allowed to name things. Hot Toggles (TM) might have been a better name for the thing. It’s really worth checking out.

An outstanding issue is how to get changed config data (JSON) to the nodes in a production stack that need it. We’ve implemented one simple mechanism for a sample Java app. In time we’d need to have code snippets (or reusable libraries) for many regular enterprise language choices.

Here’s a brain-dump of the choices, without mentioning specific languages:

Where configurable nodes access ACA (pull)

• Polling for changes on a separate thread
  • might suffer from thread death, and have restart issues
  • threads might be idiomatically incorrect for ‘container’
  • not all languages allow thread spawning
• Polling for changes associated with a end-user request
  • blocking issues?
  • Could happen ahead of serving of request
  • Could happen after the response is served

For this design to work, the configurable nodes would need authentication details for the ACA

Where ACA directly modifies configurable nodes (push)

• ACA directly pushes changed config to the nodes
  • ACA needs to authenticate with nodes, which feels backwards
  • multi-threading may help shorten the delay in updating many nodes
  • ACA has to maintain a list of the nodes that need updates
• ACA pushes changed config on to a message bus, to which the nodes subscribe
  • encryption of data on the bus could be important

Hmm, I wonder if there is a Memcache/Ehcache way of securely percolating changed config…

Where ACA merely notifies configurable nodes of ‘change’ (push)

• ACA pushes ‘some change has happened’ onto a message bus, nodes callback to ACA to pick-up changes.
  • nodes need authentication details for ACA
• ACA directly notifies nodes that ‘some change has happened’, and the nodes callback to ACA to pick-up changes.
  • nodes need auth details for ACA, but not vice versa
  • multi-threading may help shorten the delay in updating many nodes

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Dec 7, 2012: This article was syndicated by DZone