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From Konstantin Boudnik <...@apache.org>
Subject Re: About extensibility of Ambari stacks (not inheritance)
Date Tue, 02 Dec 2014 19:00:07 GMT
Thanks for chiming in, Erin! Do you know if there's any plan to have dynamic
extensibility for services? For instance, Cloudera Manager has this concept of
Custom Services. And while it was done as an added late fix for parcels, it
provides a way of adding new software components into an existing Hadoop
cluster. Which seems to be a pretty handy concept, considering the liquid
state of the whole Hadoop ecosystem.

It seems that this functionality, if desired, is going to be brand new and as
such require not just development but also re-consideration at the design
level. Am I right? Appreciate the thoughts!

The best part of active-active masters paradigm is that a client can work with
either of them without a concern of which one is ahead or behind of the rest
as they are equal. Essentially this solves some major issues that pester
active-standby solutions.

And yes, we do install the services to the cluster's nodes as you suggested in
the later part of your email - after all they are just Linux daemons (although
Ambari tries to hide the fact for whatever reason that is). However this
presents the core of the very issue: Ambari isn't aware about services
installed outside of its realm, and it doesn't provide any monitoring or
life-cycle management for those. And because of that I am trying to figure out
what can be done in this regards to have this dynamism.

With regards,
  Cos

On Tue, Dec 02, 2014 at 08:41AM, Erin Boyd wrote:
> Hi Cos,
> Currently, adding services dynamically is not supported in Ambari.  It is
> generally done, as you mentioned through the creation of a stack with the
> services definition defined within in.  I also don't believe we currently
> support multiple masters on the same cluster.  How would one deferientiate
> which master it should be using in such an environment?
> 
> Of course services can be installed independent of Ambari on the hosts
> inside the cluster...but I don't think that is what you are getting at.  Are
> you expecting the services to have a presence on the UI though installed
> outside of Ambari?
> 
> Erin
> 
> ----- Original Message -----
> From: "Konstantin Boudnik" <cos@apache.org>
> To: dev@ambari.apache.org
> Sent: Monday, December 1, 2014 6:42:30 PM
> Subject: About extensibility of Ambari stacks (not inheritance)
> 
> Guys,
> 
> I am looking into possible stack extensibility properties of Ambari (not to be
> confused with inheritance), but haven't been able to derive any final
> conclusions just yet. Hence, I'd appreciate the input from the people behind
> the system.
> 
> I have a few questions about current state of the Ambari (version 1.6.1 and
> coming 1.7, and possibly later?) with regards to ability to expand an existing
> stack definitions with a 3rd party services and do it in the runtime, rather
> than only during the installation. We need to be able to run a multiple
> instances of our master service in the cluster, which isn't typical for
> "normal" Hadoop concept where only one master can exist for any giving
> service.
> 
> Our use case is to be able to amend an exiting cluster setup (HDP, Bigtop,
> etc.) with a new service running on top of HDFS; but not to reinstall the
> whole stack. The reason we have the use case is that oftentimes our software
> is being added to an existing 3rd party environment, as an added bonus, not
> available during the initial planning and setup of the cluster.
> 
> The way I understand Ambari's stack inheritance is that a scion stack will
> be a brand new entity, e.g. I won't be able to cherry-pick services from it
> and add them to the already installed parent stack's cluster, right?
> 
> So far from I see it doesn't seem possible without introducing a brand-new
> version of a stack e.g. 'stack inheritance'. Which, unfortunately, won't work
> as per my explanation of the use above case. I guess another way to look at it
> is this: would it be possible to add a component (or a service) that will
> override an existing component or a service, but without a need to reinstall
> the rest of the stack?
> 
> Thanks in advance for any info/ideas.
>   Cos

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