i've just committed a big patch for SLIDER-782, which adds an IPC API which matches the REST API: datatypes, operations, -and which works on Hadoop 2.6 clusters with and without kerberos auth.
see org.apache.slider.client.ipc.SliderApplicationIpcClient for the implementation; the existing RpcBinder class can bind to it, using the YARN RM to provide the relevant AM token. What this lets us do is allow apps to start switching to the new RESTful API, even while using IPC underneath. Which should then make switching to (SPNEGO-authed) REST communications between client and AM something that could (almost) be hidden in the background. I say "almost" as there will inevitably be surprises related to failure modes & timing. The code works, a quick bit of refactoring and the same tests used to verify REST operations against local and functional clusters can also be applied to the IPC client. What we don't have yet is the full suite of REST operations, flexing being the key one that works in the AM today, upgrade the big project to start. Once the flex operation is done (SLIDER-713), and perhaps a container kill (we use that for testing), I could go through the SliderClient class and switch it over to the new API. Which will make it ready to work with a REST back end —add the right configuration options and we could switch to this dynamically, without needing to make a leap to an app that will only work with Hadoop 2.8+. It's not yet in the 0.70-incubating branch, but as it doesn't (currently) threaten backwards compatibility, I'm happy for it to go in -Steve
