Hello all! We introduced the CacheElement interface as part of our experimental API to update the cluster configuration. I'd like to solidify and document our intent for the interface and the extent to which it is expected to apply. In its current form, the CacheElement interface extends Serlializable and Identifiable<String>. Serialization is required for communication between members, and Identifiable is useful during lookup, modification, and removal of an existing configuration object. At our current iteration, it is not entirely clear which of our own configuration objects should or should not implement CacheElement. I think one of following interpretations may be best, but don't know which would be most natural. And, of course, if you have another that I've overlooked, I'd love to hear it.
Classes that implement CacheElement are... A) ... only custom configuration elements provided by extension developers. This declaration will appear at a top-level class declaration that is directly consumed by the CacheConfig or RegionConfig. B) ... custom configuration elements, as well as any configuration object that we wish to be searchable within the configuration. C) ... custom configuration elements, as well as any configuration object appearing at the same level in the configuration hierarchy. That is, every getter of both CacheConfig and RegionConfig should return either a CacheElement, or a List<CacheElement>. D) ... any object, excepting those in java.lang.*, that appears anywhere in the cluster configuration's hierarchy, including all inner classes. For example, ConnectorService.RegionMapping implements CacheElement. Each comes with its own potential pitfalls. Option (A) seems restrictive and sparse. Option (B) is subjective. Many classes do not have a `name' or `id' field, making option (D) difficult. I like option (C), although we have already moved beyond that specification in our current iteration, with ConnectorService.RegionMapping implementing CacheElement. Thoughts? Imagination is Change. ~Patrick Rhomberg
