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Date: Mon, 8 Dec 2014 21:24:21 +0000
From: Konstantin Boudnik <cos@apache.org>
To: dev@ambari.apache.org
Subject: Re: About extensibility of Ambari stacks (not inheritance)
Message-ID: <20141208212421.GD12785@boudnik.org>
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On Mon, Dec 08, 2014 at 04:14PM, John Speidel wrote:
> Cos,
> 
> I don't know why this is occurring.  I have not actually ever changed the
> stack of a running cluster, my response was a result of my understanding
> and talking to others that have done this.
> 
> Hopefully somebody that has actually done this can comment.
> In the meantime, I will see if I can find somebody that may may know why
> this isn't working for you.

Thank you very much - really appreciate your help! In the interest of full
disclosure: I am using 1.6.1 server, not sure if this is of any significance.

Cos

> On Fri, Dec 5, 2014 at 8:38 PM, Konstantin Boudnik <cos@apache.org> wrote:
> 
> > release Thanks for the info John. I think I am getting there, but not
> > completely....
> >
> > So, here's what I've done:
> > - added service, bounced Ambari server
> >
> > - curl to http://vmhost05-hbase3.bdva.wandisco.com:8080/api/v1/stacks/HDP/
> > says that I have new stack
> >     {
> >       "href" : "
> > http://vmhost05-hbase3.bdva.wandisco.com:8080/api/v1/stacks/HDP/versions/2.1.WANdisco
> > ",
> >       "Versions" : {
> >         "stack_name" : "HDP",
> >         "stack_version" : "2.1.WANdisco"
> >       }
> >     }
> >
> > - ran update
> >   curl -u admin:admin -i -X PUT -H  'X-Requested-By: ambari' -d
> > '{"Clusters":{"version":"HDP-2.1.WANdisco"}}'
> > http://vmhost05-hbase3.bdva.wandisco.com:8080/api/v1/clusters/DC-2
> >
> > The result was:
> > HTTP/1.1 200 OK
> > Set-Cookie: AMBARISESSIONID=vueucwdh8p6mkmcygj803vi9;Path=/
> > Expires: Thu, 01 Jan 1970 00:00:00 GMT
> > Content-Type: text/plain
> > Content-Length: 0
> > Server: Jetty(7.6.7.v20120910)
> >
> > However, running
> >         curl -u admin:admin
> > http://vmhost05-hbase3.bdva.wandisco.com:8080/api/v1/clusters/
> >
> > Still gives me this....
> > {
> >   "href" : "http://vmhost05-hbase3.bdva.wandisco.com:8080/api/v1/clusters/
> > ",
> >   "items" : [
> >     {
> >       "href" : "
> > http://vmhost05-hbase3.bdva.wandisco.com:8080/api/v1/clusters/DC-2",
> >       "Clusters" : {
> >         "cluster_name" : "DC-2",
> >         "version" : "HDP-2.1"
> >       }
> >     }
> >   ]
> >
> > Any ideas/hints? Thank you very much for your help!
> >   Cos
> >
> > On Thu, Dec 04, 2014 at 08:08PM, John Speidel wrote:
> > > Cos,
> > >
> > > Yes, if you are able to push a new stack to the ambari server hosts
> > > filesystem, you can use a REST api call to update the cluster to be
> > > associated with the new stack.
> > >
> > > So, the steps would would look like this:
> > > - install cluster with existing stack
> > > - create new stack with additional services/components
> > > - write the new stack to the filesystem of the ambari server host
> > > - bounce ambari server
> > >   -- after the server restart, the hash of the stacks directory is
> > > recalculated which will result in the new updated stack to be pushed to
> > the
> > > agents (not immediate, the check of the stack dir hash occurs every n(not
> > > sure of exact value) heartbeats from the agents)
> > > - do an update (PUT)  on the cluster resource changing the value of the
> > > Clusters/version property to point to the new stack
> > >
> > > When these steps are completed the new service/components should be
> > > recognized by ambari.
> > >
> > > -John
> > >
> > >
> > > On Thu, Dec 4, 2014 at 6:07 PM, Konstantin Boudnik <cos@apache.org>
> > wrote:
> > >
> > > > Hi John.
> > > >
> > > > Thanks for more info. I'd like to pry more for a little bit of
> > information
> > > > (in-lined):
> > > >
> > > > On Thu, Dec 04, 2014 at 04:19PM, John Speidel wrote:
> > > > > Hi Cos,
> > > > > As mentioned above, it isn't currently possible to augment an
> > existing
> > > > > stack at runtime with new services/components.  You could possibly
> > change
> > > > > the stack associated with a running cluster to a new stack which
> > contains
> > > > > the required services/components, but this new stack definition would
> > > > need
> > > > > to be available to ambari so it really isn't very dynamic.  We
> > understand
> > > >
> > > > Let me describe this scenario as I understood this. Let's say I have
> > two
> > > > stacks:
> > > >   - StackA (with usual set of components), currently installed on a
> > cluster
> > > >   - StackB == StackA + ComponentX
> > > > So, if I add StackB definition to the Ambari server and restart it,
> > will I
> > > > be
> > > > able to switch from StackA to StackB _without_ resintalling the
> > cluster,
> > > > and
> > > > then add/configure ComponentX's service?
> > > >
> > > > If my depiction is correct then it might be an acceptable workaround
> > in the
> > > > absence of dynamic extensibility.
> > > >
> > > > > that going forward that the stack framework will need to be more
> > > > extensible
> > > > > and dynamic as additional stack definitions are created.  Some of the
> > > > > underlying work to make stack processing more flexible has already
> > been
> > > > > done in anticipation of new requirements in this area.
> > > >
> > > > Shivaji Dutta, in an offline email exchange, pointed me to AMBARI-7175
> > and
> > > > AMBARI-7201, which is seemingly going into the right direction, but
> > still
> > > > would require a stack re-definition, if I read it right.
> > > >
> > > > > This is actually the second time that this scenario has came up for
> > me
> > > > > today so it would be nice to get a Jira filed for an enhancement
> > where
> > > > the
> > > > > community can start to discuss the associated use cases.
> > > >
> > > > I will start a JIRA and put together the set of requirements.
> > > >
> > > > Regards,
> > > >   Cos
> > > >
> > > > > -John
> > > > >
> > > > > On Tue, Dec 2, 2014 at 2:00 PM, Konstantin Boudnik <cos@apache.org>
> > > > wrote:
> > > > >
> > > > > > 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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