Hi! TL;DR: Populating images in the image cache.
I'm working on a fix for JCLOUDS-588 [1] and I have a first implementation [2]. However, before submitting a pull request I want to validate it here. Basically the issue is the population of the image cache. When using the ComputeService, jclouds caches the list of images (as it can be an expensive operation) in a memoized supplier. That cache is used by the TemplateBuilder, the default ComputeServiceAdapter and by most of the classes in the compute abstraction, to avoid making unnecessary expensive calls to the provider. There are, at least, two cases in which the use of this cache is leading to images not being found: * When images are created with the ImageExtension (see JCLOUDS-512 [3]). * When providers don't return some images when listing them but a "getById" call works (see JCLOUDS-570 [1]). IMO, the safest approach to fix this is to populate the missing images in the cache as soon as we find them. The challenging thing is that the image cache is currently implemented as a memoized supplier, which is basically a singleton immutable set, so we can't write to it or copy it to a new instance, as there are many classes that will have it already injected. In the current patch I'm working on, I've created an ImageCacheSupplier [5] that acts as a "view" of that memoized supplier. It provides a "registerImage" method to register the discovered images, and it returns the composition of both, the cached and discovered ones when someone calls its "get()" method. That ImageCacheSupplier replaces the current memoized supplier, so it is by default injected in all providers. And my questions are: * We have to manually populate the images in the cache as soon as we know they're missing. This is obvious in the template builder and the image extension. Do you have in mind any other case or place in the code where we should take care of populating images? (Doing this by default can be overkill as noted in JCLOUDS-588 comments, so we'd better identify where we might find unknown images and register them there). * Do you have in mind an alternate/better approach to this one? :) Thanks! Ignasi [1] https://issues.apache.org/jira/browse/JCLOUDS-588 [2] https://github.com/nacx/jclouds/tree/588-imagecache [3] https://issues.apache.org/jira/browse/JCLOUDS-512 [4] https://issues.apache.org/jira/browse/JCLOUDS-570 [5] https://github.com/nacx/jclouds/blob/588-imagecache/compute/src/main/java/org/jclouds/compute/suppliers/ImageCacheSupplier.java
