In fabric8 1.x we assumed only a JVM was available and then we built lots of abstractions that are very similar to Kubernetes.
Because of this approach we do quite a few things a little differently under the covers. In fabric8 1.x we had to do a lot of work to replicate the kinds of things Kubernetes gives us; things like discovery of services, wiring, auto scaling etc.
However as an end user writing, say, Java applications or using technologies like ActiveMQ, Camel or containers like Karaf, Tomcat, WildFly or Spring Boot things should seem pretty similar; though in many ways things get much simpler now (as discovery, wiring and packaging is now simpler and more standardised).
The aim of fabric8 on Kubernetes is still to support any runtime application server or software distribution at all; though docker containers will be the standard mechanism for packaging and running software. The change from 1.x to 2.x does not mean any application servers are no longer supported; it's the reverse - now any docker image is supported ;).
If you have been using fabric8 1.x up to now and have maven builds making profiles; all that really changes is how the build gets packaged into containers.
i.e. your maven builds which create jars, bundles, wars and so forth are all totally valid and supported.
fabric8 2.x builds just support a different way to automatically turn your deployment units into docker containers for deployment on fabric8.
In addition the use of Apps allows you to define replication controllers (to specify how many instances of a container you need) as a single deployment JSON. You can also compose multiple containers together and orchestrate them into a single App JSON file.
Finally thanks to Services the wiring of your components to their services becomes much simpler; usually it's just a case of using an environment variable for the service port (with a nice default value).
Instead of using a ZooKeeper registry in 1.x to store all service endpoints so that we could inject them into other services using property resolvers; we instead use the Services abstraction in Kubernetes. This means clients of a network service just bind to a fixed port on the local network; there's no need to have any complex wiring inside the application.
This radically simplifies applications. For example any application using ActiveMQ just needs to bind to the localhost and port of the region of the ActiveMQ cluster. For many Camel endpoints, the endpoint just needs to choose which port number maps to the service it needs to bind to for things like databases.
In fabric8 1.x we focused on profiles in a wiki which are used to represent configuration and metadata which provides a mechanism to build profiles into a container.
In addition to support the ability to modify source or metadata inside a wiki / git repository (e.g. camel routes or Java code) we default to using the Kubernetes source to image extension. i.e. Profiles map to a build which has a git repository; this can be viewed/edited via the wiki, a web based IDE or traditional IDE or editor.
So source projects are edited; they result in builds which then generate container images which are then used by deployments.
In fabric8 1.x we used requirements we specified on a Profile basis. In 2.x we use Replication Controller definitions in JSON to specify how many instances of a certain pod (container) we need to run.
In Kubernetes each pod (or container) gets its own IP address; and the internal container ports and external host ports are then constant; making things much easier to use and wire together.
This is quite different to using fabric8 1.x where depending on the underlying container provider port allocations were different. e.g. by default host and container ports were dynamically generated; for docker internal container ports were constant but external host ports were dynamic.
From the implementation perspective V2 is a big change but we see this as an evolutionary change for users of fabric8 in V2:
In many ways 1.x of fabric8 was a set of quickstarts, runtimes, libraries, a console and a Kubernetes-like layer all combined into a single project (with V1 Gateway being very like Kubernetes Services). So to create containers we have a REST API and CLI.
So in 2.x of fabric8 we use the exact same quickstarts, runtimes, libraries and console. The web console is still hawtio; it's got all the same tooling for ActiveMQ, Camel, CXF, OSGi; it's got a wiki based on a git repository. The difference is it uses the Kubernetes REST API to create containers (rather than the fabric8 1.x one) and uses the Kubernetes CLI.
Another side benefit of V2 is that less wiring Java code is required. e.g. any library using ActiveMQ or the camel-activemq component no longer needs to specify a brokerURL or include custom discovery code; it can just set the AMQ_PORT environment variable to point to the service port for the broker group (e.g. the regional cluster of ActiveMQ required) so that the code connects to localhost and Kubernetes Services does the rest! Note this also works for all programming languages and clients too.
Kubernetes/OpenShift ships with etcd today and uses that to manage the minions. So a fabric8 cluster may be able to reuse the underlying etcd to do things like master election, partitioning etc.
Though depending on multi tenant requirements; applications might not be allowed to reuse the same etcd as an Kubernetes/OpenShift installation. e.g. OpenShift Online with 2 million apps probably isn't gonna let any user application just read and write lots of data to the global etcd ;).
So there will still be a need to provision clusters of etcd or ZooKeeper for use inside an application. Given the use of etcd inside Kubernetes/OpenShift then it might be more typical to create sub-clusters (or have a kind of partitioned etcd cluster).
Though from the fabric8 project we're aiming to provide an abstraction layer so when master election / partitionining is required in Java code we can use either etcd or ZK clusters; and can - if allowed - reuse the same underlying etcd cluster.
Incidentally the V2 way to provision an ensemble of ZooKeeper or etcd cluster is probably going to be via an App which makes it easier to provision; then clients can use Services to connect to it. So V2 should make the creation of ensembles easier and more standardised across the hybrid clouds.
Absolutely! :) In many ways the move to V2 makes it much easier to support any language, framework or application server as we can reuse all of the Docker ecosystem of images in V2.
So nothing is going away. V2 just standardises things to make them easier to consume, describe, support and makes things more reusable. For example, you can take your docker container image anywhere that can run docker and take your App JSON to any Kubernetes environment (like OpenShift Online, OpenShift Enterprise, Google Compute Engine, Azure, VMWare etc.). They'd be easy to port to run natively on any place docker runs too really (e.g. EC2).