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From Nick Allen <n...@nickallen.org>
Subject Re: [DISCUSS] Ambari Metron Configuration Management consequences and call to action
Date Fri, 13 Jan 2017 15:52:52 GMT
Makes sense, Dave.  I am totally clear on the proposal.  I just wanted to
ask the stupid question to bring the conversation full circle, leave no
stone unturned, insert favorite idiom here.

On Fri, Jan 13, 2017 at 10:46 AM, David Lyle <dlyle65535@gmail.com> wrote:

> To be clear- NOBODY is suggesting replacing Zookeeper with Ambari.
>
> So, as a bit of a reset- here's what's being proposed:
>
>  - Expand ambari to manage the remaining sensor-specific configs
>  - Refactor the push calls to zookeeper (in ConfigurationUtils, I think)
>    to push to ambari and take an Ambari user/pw and (optionally) reason
>  - (Ambari can push to zookeeper, but it requires a service restart, so for
> "live changes" you may
>     want do both a rest call and zookeeper update from ConfigurationUtils)
>     WAS
>     Question remains about whether ambari can do the push to zookeeper
>     or whetheror whether ConfigurationUtils has to push to zookeeper as
> well as update
>     ambari.
>   - Refactor the middleware that Ryan submitted to have the API calls take
>      an Ambari user/pw and (optionally) reason
>   - Refactor the management UI to pass in an Ambari user/pw and
> (optionally) reason
>   - Refactor the Stellar Management functions CONFIG_PUT to accept an
> Ambari user/pw and (optionally) reason
>
> -D...
>
>
>
> On Fri, Jan 13, 2017 at 10:42 AM, Ryan Merriman <merrimanr@gmail.com>
> wrote:
>
> > The driver for using Zookeeper is that it is asynchronous and accepts
> > callbacks.  Ambari would need to have that capability, otherwise we have
> to
> > poll which is a deal breaker in my opinion.
> >
> > On Fri, Jan 13, 2017 at 9:28 AM, Casey Stella <cestella@gmail.com>
> wrote:
> >
> > > No, it was good to bring up, Nick.  I might have it wrong re: Ambari.
> > >
> > > Casey
> > >
> > > On Fri, Jan 13, 2017 at 10:27 AM, Nick Allen <nick@nickallen.org>
> wrote:
> > >
> > > > That makes sense.  I wasn't sure based on Matt's original
> > > > suggestion/description of Ambari, whether that was something that
> > Ambari
> > > > had also designed for or not.
> > > >
> > > > On Fri, Jan 13, 2017 at 10:14 AM, Casey Stella <cestella@gmail.com>
> > > wrote:
> > > >
> > > > > Polling the Ambari server via REST (or their API if they have one),
> > > would
> > > > > entail all workers hitting one server and create a single point of
> > > > failure
> > > > > (the ambari server is what serves up REST).  Zookeeper's intent is
> to
> > > not
> > > > > have a single point of failure like this and (one of its main)
> > > use-cases
> > > > is
> > > > > to serve up configs in a distributed environment.
> > > > >
> > > > > Casey
> > > > >
> > > > > On Fri, Jan 13, 2017 at 9:55 AM, Nick Allen <nick@nickallen.org>
> > > wrote:
> > > > >
> > > > > > Let me ask a stupid question.  What does Zookeeper do for us
that
> > > > Ambari
> > > > > > cannot?  Why keep Zookeeper in the mix?
> > > > > >
> > > > > >
> > > > > >
> > > > > > On Fri, Jan 13, 2017 at 9:28 AM, David Lyle <
> dlyle65535@gmail.com>
> > > > > wrote:
> > > > > >
> > > > > > > In the main yes- I've made some changes:
> > > > > > >
> > > > > > >  - Expand ambari to manage the remaining sensor-specific
> configs
> > > > > > >  - Refactor the push calls to zookeeper (in
> ConfigurationUtils, I
> > > > > think)
> > > > > > >    to push to ambari and take an Ambari user/pw and
> (optionally)
> > > > reason
> > > > > > >  - (Ambari can push to zookeeper, but it requires a service
> > > restart,
> > > > so
> > > > > > for
> > > > > > > "live changes" you may
> > > > > > >     want do both a rest call and zookeeper update from
> > > > > > ConfigurationUtils)
> > > > > > >     WAS
> > > > > > >     Question remains about whether ambari can do the push
to
> > > > zookeeper
> > > > > > >     or whetheror whether ConfigurationUtils has to push
to
> > > zookeeper
> > > > as
> > > > > > > well as update
> > > > > > >     ambari.
> > > > > > >   - Refactor the middleware that Ryan submitted to have
the API
> > > calls
> > > > > > take
> > > > > > >      an Ambari user/pw and (optionally) reason
> > > > > > >   - Refactor the management UI to pass in an Ambari user/pw
and
> > > > > > > (optionally) reason
> > > > > > >   - Refactor the Stellar Management functions CONFIG_PUT
to
> > accept
> > > an
> > > > > > > Ambari user/pw and (optionally) reason
> > > > > > >
> > > > > > > I think we'd need to do some detailed design around how
to
> handle
> > > > what
> > > > > we
> > > > > > > expect to be dynamic configs, but the main principle should
> (imo)
> > > be
> > > > to
> > > > > > > always know who and why and make sure that Ambari is aware
and
> is
> > > the
> > > > > > > static backing store for Zookeeper.
> > > > > > >
> > > > > > > -D...
> > > > > > >
> > > > > > >
> > > > > > > On Fri, Jan 13, 2017 at 9:19 AM, Casey Stella <
> > cestella@gmail.com>
> > > > > > wrote:
> > > > > > >
> > > > > > > > So, basically, your proposed changes, broken into
tangible
> > > gobbets
> > > > of
> > > > > > > work:
> > > > > > > >
> > > > > > > >    - Expand ambari to manage the remaining sensor-specific
> > > configs
> > > > > > > >    - Refactor the push calls to zookeeper (in
> > > ConfigurationUtils, I
> > > > > > > think)
> > > > > > > >    to push to ambari and take a reason
> > > > > > > >       - Question remains about whether ambari can
do the push
> > to
> > > > > > > zookeeper
> > > > > > > >       or whether ConfigurationUtils has to push to
zookeeper
> as
> > > > well
> > > > > as
> > > > > > > > update
> > > > > > > >       ambari.
> > > > > > > >    - Refactor the middleware that Ryan submitted to
have the
> > API
> > > > > calls
> > > > > > > take
> > > > > > > >    a reason
> > > > > > > >    - Refactor the management UI to pass in a reason
> > > > > > > >    - Refactor the Stellar Management functions CONFIG_PUT
to
> > > > accept a
> > > > > > > > reason
> > > > > > > >
> > > > > > > > Just so we can evaluate it and I can ensure I haven't
> > overlooked
> > > > some
> > > > > > > > important point.  Please tell me if Ambari cannot
do the
> things
> > > > we're
> > > > > > > > suggesting it can do.
> > > > > > > >
> > > > > > > > Casey
> > > > > > > >
> > > > > > > > On Fri, Jan 13, 2017 at 9:15 AM, David Lyle <
> > > dlyle65535@gmail.com>
> > > > > > > wrote:
> > > > > > > >
> > > > > > > > > That's exactly correct, Casey. Basically, an
expansion of
> > what
> > > > > we're
> > > > > > > > > currently doing with global.json, enrichment.properties
and
> > > > > > > > > elasticsearch.properties.
> > > > > > > > >
> > > > > > > > > -D...
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > On Fri, Jan 13, 2017 at 9:12 AM, Casey Stella
<
> > > > cestella@gmail.com>
> > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > > I would suggest not having Ambari replace
zookeeper.  I
> > think
> > > > the
> > > > > > > > > proposal
> > > > > > > > > > is to have Ambari replace the editable store
(like the
> JSON
> > > > files
> > > > > > on
> > > > > > > > > > disk).  Zookeeper woudl be the source of
truth for the
> > > running
> > > > > > > > topologies
> > > > > > > > > > and ambari would be sync'd to it.
> > > > > > > > > >
> > > > > > > > > > Correct if I misspeak, dave or matt.
> > > > > > > > > >
> > > > > > > > > > Casey
> > > > > > > > > >
> > > > > > > > > > On Fri, Jan 13, 2017 at 9:09 AM, Nick Allen
<
> > > > nick@nickallen.org>
> > > > > > > > wrote:
> > > > > > > > > >
> > > > > > > > > > > Ambari seems like a logical choice.
> > > > > > > > > > >
> > > > > > > > > > > *>> It doesn’t natively integrate
Zookeeper storage of
> > > > configs,
> > > > > > but
> > > > > > > > > there
> > > > > > > > > > > is a natural place to specify copy
to/from Zookeeper
> for
> > > the
> > > > > > files
> > > > > > > > > > > desired.*
> > > > > > > > > > >
> > > > > > > > > > > How would Ambari interact with Zookeeper
in this
> > scenario?
> > > > > Would
> > > > > > > > > Ambari
> > > > > > > > > > > replace Zookeeper completely? Or would
Zookeeper act as
> > the
> > > > > > > > persistence
> > > > > > > > > > > tier under Ambari?
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > On Thu, Jan 12, 2017 at 9:24 PM, Matt
Foley <
> > > > mattf@apache.org>
> > > > > > > > wrote:
> > > > > > > > > > >
> > > > > > > > > > > > Mike, could you try again on the
image, please,
> making
> > > sure
> > > > > it
> > > > > > > is a
> > > > > > > > > > > simple
> > > > > > > > > > > > format (gif, png, or jpeg)?  It
got munched, at least
> > in
> > > my
> > > > > > > viewer.
> > > > > > > > > > > Thanks.
> > > > > > > > > > > >
> > > > > > > > > > > > Casey, responding to some of the
questions you
> raised:
> > > > > > > > > > > >
> > > > > > > > > > > > I’m going to make a rather strong
statement:  We
> > already
> > > > > have a
> > > > > > > > > service
> > > > > > > > > > > > “to intermediate and handle
config update/retrieval”.
> > > > > > > > > > > > Furthermore, it:
> > > > > > > > > > > > - Correctly handles the problems
of distributed
> > services
> > > > > > running
> > > > > > > on
> > > > > > > > > > > > multi-node clusters.  (That’s
a HARD problem, people,
> > and
> > > > we
> > > > > > > > > shouldn’t
> > > > > > > > > > > try
> > > > > > > > > > > > to reinvent the wheel.)
> > > > > > > > > > > > - Correctly handles Kerberos security.
(That’s kinda
> > hard
> > > > > too,
> > > > > > or
> > > > > > > > at
> > > > > > > > > > > least
> > > > > > > > > > > > a lot of work.)
> > > > > > > > > > > > - It does automatic versioning
of configurations, and
> > > > allows
> > > > > > > > viewing,
> > > > > > > > > > > > comparing, and reverting historical
configs
> > > > > > > > > > > > - It has a capable REST API for
all those things.
> > > > > > > > > > > > It doesn’t natively integrate
Zookeeper storage of
> > > configs,
> > > > > but
> > > > > > > > there
> > > > > > > > > > is
> > > > > > > > > > > a
> > > > > > > > > > > > natural place to specify copy
to/from Zookeeper for
> the
> > > > files
> > > > > > > > > desired.
> > > > > > > > > > > >
> > > > > > > > > > > > It is Ambari.  And we should commit
to it, rather
> than
> > > try
> > > > to
> > > > > > > > > re-create
> > > > > > > > > > > > such features.
> > > > > > > > > > > > Because it has a good REST API,
it is perfectly
> > feasible
> > > to
> > > > > > > > implement
> > > > > > > > > > > > Stellar functions that call it.
> > > > > > > > > > > > GUI configuration tools can also
use the Ambari APIs,
> > or
> > > > > better
> > > > > > > yet
> > > > > > > > > be
> > > > > > > > > > > > integrated in an “Ambari View”.
(Eg, see the “Yarn
> > > Capacity
> > > > > > > > Scheduler
> > > > > > > > > > > > Configuration Tool” example
in the Ambari
> > documentation,
> > > > > under
> > > > > > > > “Using
> > > > > > > > > > > > Ambari Views”.)
> > > > > > > > > > > >
> > > > > > > > > > > > Arguments are: Parsimony, Sufficiency,
Not
> reinventing
> > > the
> > > > > > wheel,
> > > > > > > > and
> > > > > > > > > > Not
> > > > > > > > > > > > spending weeks and weeks of developer
time over the
> > next
> > > > year
> > > > > > > > > > reinventing
> > > > > > > > > > > > the wheel while getting details
wrong multiple times…
> > > > > > > > > > > >
> > > > > > > > > > > > Okay, off soapbox.
> > > > > > > > > > > >
> > > > > > > > > > > > Casey asked what the config update
behavior of Ambari
> > is,
> > > > and
> > > > > > how
> > > > > > > > it
> > > > > > > > > > will
> > > > > > > > > > > > interact with changes made from
outside Ambari.
> > > > > > > > > > > > The following is from my experience
working with the
> > > Ambari
> > > > > > Mpack
> > > > > > > > for
> > > > > > > > > > > > Metron.  I am not otherwise an
Ambari expert, so
> > tomorrow
> > > > > I’ll
> > > > > > > get
> > > > > > > > it
> > > > > > > > > > > > reviewed by an Ambari development
engineer.
> > > > > > > > > > > >
> > > > > > > > > > > > Ambari-server runs on one node,
and Ambari-agent runs
> > on
> > > > each
> > > > > > of
> > > > > > > > all
> > > > > > > > > > the
> > > > > > > > > > > > nodes.
> > > > > > > > > > > > Ambari-server has a private set
of py, xml, and
> > template
> > > > > files,
> > > > > > > > which
> > > > > > > > > > > > together are used both to generate
the Ambari
> > > configuration
> > > > > > GUI,
> > > > > > > > with
> > > > > > > > > > > > defaults, and to generate configuration
files (of any
> > > > needed
> > > > > > > > > filetype)
> > > > > > > > > > > for
> > > > > > > > > > > > the various Stack components.
> > > > > > > > > > > > Ambari-server also has a database
where it stores the
> > > > schema
> > > > > > > > related
> > > > > > > > > to
> > > > > > > > > > > > these files, so even if you reach
in and edit
> Ambari’s
> > > > files,
> > > > > > it
> > > > > > > > will
> > > > > > > > > > > Error
> > > > > > > > > > > > out if the set of parameters or
parameter names
> > changes.
> > > > The
> > > > > > > > > > historical
> > > > > > > > > > > > information about configuration
changes is also
> stored
> > in
> > > > the
> > > > > > db.
> > > > > > > > > > > > For each component (and in the
case of Metron, for
> each
> > > > > > > topology),
> > > > > > > > > > there
> > > > > > > > > > > > is a python file which controls
the logic for these
> > > > actions,
> > > > > > > among
> > > > > > > > > > > others:
> > > > > > > > > > > > - Install
> > > > > > > > > > > > - Start / stop / restart / status
> > > > > > > > > > > > - Configure
> > > > > > > > > > > >
> > > > > > > > > > > > It is actually up to this python
code (which we wrote
> > for
> > > > the
> > > > > > > > Metron
> > > > > > > > > > > > Mpack) what happens in each of
these API calls.  But
> > the
> > > > > > current
> > > > > > > > > code,
> > > > > > > > > > > and
> > > > > > > > > > > > I believe this is typical of Ambari-managed
> components,
> > > > > > performs
> > > > > > > a
> > > > > > > > > > > > “Configure” action whenever
you press the “Save”
> button
> > > > after
> > > > > > > > > changing
> > > > > > > > > > a
> > > > > > > > > > > > component config in Ambari, and
also on each Install
> > and
> > > > > Start
> > > > > > or
> > > > > > > > > > > Restart.
> > > > > > > > > > > >
> > > > > > > > > > > > The Configure action consists
of approximately the
> > > > following
> > > > > > > > sequence
> > > > > > > > > > > (see
> > > > > > > > > > > > disclaimer above :-)
> > > > > > > > > > > > - Recreate the generated config
files, using the
> > template
> > > > > files
> > > > > > > and
> > > > > > > > > the
> > > > > > > > > > > > actual configuration most recently
set in Ambari
> > > > > > > > > > > > o Note this is also under the
control of python code
> > that
> > > > we
> > > > > > > wrote,
> > > > > > > > > and
> > > > > > > > > > > > this is the appropriate place
to push to ZK if
> desired.
> > > > > > > > > > > > - Propagate those config files
to each Ambari-agent,
> > > with a
> > > > > > > command
> > > > > > > > > to
> > > > > > > > > > > set
> > > > > > > > > > > > them locally
> > > > > > > > > > > > - The ambari-agents on each node
receive the files
> and
> > > > write
> > > > > > them
> > > > > > > > to
> > > > > > > > > > the
> > > > > > > > > > > > specified locations on local storage
> > > > > > > > > > > >
> > > > > > > > > > > > Ambari-server then whines that
the updated services
> > > should
> > > > be
> > > > > > > > > > restarted,
> > > > > > > > > > > > but does not initiate that action
itself (unless of
> > > course
> > > > > the
> > > > > > > > > > initiating
> > > > > > > > > > > > action was a Start command from
the administrator).
> > > > > > > > > > > >
> > > > > > > > > > > > Make sense?  It’s all quite
straightforward in
> concept,
> > > > > there’s
> > > > > > > > just
> > > > > > > > > an
> > > > > > > > > > > > awful lot of stuff wrapped around
that to make it all
> > go
> > > > > > smoothly
> > > > > > > > and
> > > > > > > > > > > > handle the problems when it doesn’t.
> > > > > > > > > > > >
> > > > > > > > > > > > There’s additional complexity
in that the
> Ambari-agent
> > > also
> > > > > > > caches
> > > > > > > > > (on
> > > > > > > > > > > > each node) both the template files
and COMPILED forms
> > of
> > > > the
> > > > > > > python
> > > > > > > > > > files
> > > > > > > > > > > > (.pyc) involved in transforming
them.  The pyc files
> > > > > > incorporate
> > > > > > > > some
> > > > > > > > > > > > amount of additional info regarding
parameter values,
> > but
> > > > I’m
> > > > > > not
> > > > > > > > > sure
> > > > > > > > > > of
> > > > > > > > > > > > the form.  I don’t think that
changes the above in
> any
> > > > > > practical
> > > > > > > > way
> > > > > > > > > > > unless
> > > > > > > > > > > > you’re trying to cheat Ambari
by reaching in and
> > editing
> > > > its
> > > > > > > files
> > > > > > > > > > > > directly.  In that case, you also
need to whack the
> pyc
> > > > files
> > > > > > (on
> > > > > > > > > each
> > > > > > > > > > > > node) to force the data to be
reloaded from
> > > Ambari-server.
> > > > > > Best
> > > > > > > > > > solution
> > > > > > > > > > > > is don’t cheat.
> > > > > > > > > > > >
> > > > > > > > > > > > Also, there may be circumstances
under which the
> > > > Ambari-agent
> > > > > > > will
> > > > > > > > > > detect
> > > > > > > > > > > > changes and re-write the latest
version it knows of
> the
> > > > > config
> > > > > > > > files,
> > > > > > > > > > > even
> > > > > > > > > > > > without a Save or Start action
at the Ambari-server.
> > I’m
> > > > not
> > > > > > > sure
> > > > > > > > of
> > > > > > > > > > > this
> > > > > > > > > > > > and need to check with Ambari
developers.  It may no
> > > longer
> > > > > > > happen,
> > > > > > > > > > altho
> > > > > > > > > > > > I’m pretty sure change detection/reversion
was a
> > feature
> > > of
> > > > > > early
> > > > > > > > > > > versions
> > > > > > > > > > > > of Ambari.
> > > > > > > > > > > >
> > > > > > > > > > > > Hope this helps,
> > > > > > > > > > > > --Matt
> > > > > > > > > > > >
> > > > > > > > > > > > ================================================
> > > > > > > > > > > > From: Michael Miklavcic <michael.miklavcic@gmail.com
> >
> > > > > > > > > > > > Reply-To: "dev@metron.incubator.apache.org"
> > > > > > > > > > > <dev@metron.incubator.apache.
> > > > > > > > > > > > org>
> > > > > > > > > > > > Date: Thursday, January 12, 2017
at 3:59 PM
> > > > > > > > > > > > To: "dev@metron.incubator.apache.org"
> > > > > > > > <dev@metron.incubator.apache.
> > > > > > > > > org
> > > > > > > > > > >
> > > > > > > > > > > > Subject: Re: [DISCUSS] Ambari
Metron Configuration
> > > > Management
> > > > > > > > > > > consequences
> > > > > > > > > > > > and call to action
> > > > > > > > > > > >
> > > > > > > > > > > > Hi Casey,
> > > > > > > > > > > >
> > > > > > > > > > > > Thanks for starting this thread.
I believe you are
> > > correct
> > > > in
> > > > > > > your
> > > > > > > > > > > > assessment of the 4 options for
updating configs in
> > > Metron.
> > > > > > When
> > > > > > > > > using
> > > > > > > > > > > more
> > > > > > > > > > > > than one of these options we can
get into a
> split-brain
> > > > > > > scenario. A
> > > > > > > > > > basic
> > > > > > > > > > > > example is updating the global
config on disk and
> using
> > > the
> > > > > > > > > > > > zk_load_configs.sh. Later, if
a user decides to
> restart
> > > > > Ambari,
> > > > > > > the
> > > > > > > > > > > cached
> > > > > > > > > > > > version stored by Ambari (it's
in the MySQL or other
> > > > database
> > > > > > > > backing
> > > > > > > > > > > > Ambari) will be written out to
disk in the defined
> > config
> > > > > > > > directory,
> > > > > > > > > > and
> > > > > > > > > > > > subsequently loaded using the
zk_load_configs.sh
> under
> > > the
> > > > > > hood.
> > > > > > > > Any
> > > > > > > > > > > global
> > > > > > > > > > > > configuration modified outside
of Ambari will be lost
> > at
> > > > this
> > > > > > > > point.
> > > > > > > > > > This
> > > > > > > > > > > > is obviously undesirable, but
I also like the purpose
> > and
> > > > > > utility
> > > > > > > > > > exposed
> > > > > > > > > > > > by the multiple config management
interfaces we
> > currently
> > > > > have
> > > > > > > > > > > available. I
> > > > > > > > > > > > also agree that a service would
be best.
> > > > > > > > > > > >
> > > > > > > > > > > > For reference, here's my understanding
of the current
> > > > > > > configuration
> > > > > > > > > > > > loading mechanisms and their deps.
> > > > > > > > > > > >
> > > > > > > > > > > > <image>
> > > > > > > > > > > >
> > > > > > > > > > > > Mike
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > On Thu, Jan 12, 2017 at 3:08 PM,
Casey Stella <
> > > > > > > cestella@gmail.com>
> > > > > > > > > > > wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > In the course of discussion on
the PR for METRON-652
> > > > > > > > > > > > <https://github.com/apache/incubator-metron/pull/415
> >
> > > > > > something
> > > > > > > > > that I
> > > > > > > > > > > > should definitely have understood
better came to
> light
> > > and
> > > > I
> > > > > > > > thought
> > > > > > > > > > that
> > > > > > > > > > > > it was worth bringing to the attention
of the
> community
> > > to
> > > > > get
> > > > > > > > > > > > clarification/discuss is just
how we manage configs.
> > > > > > > > > > > >
> > > > > > > > > > > > Currently (assuming the management
UI that Ryan
> > Merriman
> > > > > > > submitted)
> > > > > > > > > > > configs
> > > > > > > > > > > > are managed/adjusted via a couple
of different
> > mechanism.
> > > > > > > > > > > >
> > > > > > > > > > > >    - zk_load_utils.sh: pushed
and pulled from disk to
> > > > > zookeeper
> > > > > > > > > > > >    - Stellar REPL: pushed and
pulled via the
> > > > > > > CONFIG_GET/CONFIG_PUT
> > > > > > > > > > > > functions
> > > > > > > > > > > >    - Ambari: initialized via the
zk_load_utils script
> > and
> > > > > then
> > > > > > > some
> > > > > > > > > of
> > > > > > > > > > > them
> > > > > > > > > > > >    are managed directly (global
config) and some
> > > indirectly
> > > > > > > > > > > > (sensor-specific
> > > > > > > > > > > >    configs).
> > > > > > > > > > > >       - NOTE: Upon service restart,
it may or may not
> > > > > overwrite
> > > > > > > > > changes
> > > > > > > > > > > on
> > > > > > > > > > > >       disk or on zookeeper.  *Can
someone more
> > > > knowledgeable
> > > > > > than
> > > > > > > > me
> > > > > > > > > > > about
> > > > > > > > > > > >       this describe precisely
the semantics that we
> can
> > > > > expect
> > > > > > on
> > > > > > > > > > > > service restart
> > > > > > > > > > > >       for Ambari? What gets overwritten
on disk and
> > what
> > > > gets
> > > > > > > > updated
> > > > > > > > > > > > in ambari?*
> > > > > > > > > > > >    - The Management UI: manages
some of the configs.
> > > *RYAN:
> > > > > > Which
> > > > > > > > > > configs
> > > > > > > > > > > >    do we support here and which
don't we support
> here?*
> > > > > > > > > > > >
> > > > > > > > > > > > As you can see, we have a mishmash
of mechanisms to
> > > update
> > > > > and
> > > > > > > > manage
> > > > > > > > > > the
> > > > > > > > > > > > configuration for Metron in zookeeper.
 In the
> > beginning
> > > > the
> > > > > > > > approach
> > > > > > > > > > was
> > > > > > > > > > > > just to edit configs on disk and
push/pull them via
> > > > > > > zk_load_utils.
> > > > > > > > > > > Configs
> > > > > > > > > > > > could be historically managed
using source control,
> > etc.
> > > > As
> > > > > we
> > > > > > > got
> > > > > > > > > > more
> > > > > > > > > > > > and more components managing the
configs, we haven't
> > > taken
> > > > > care
> > > > > > > > that
> > > > > > > > > > they
> > > > > > > > > > > > they all work with each other
in an expected way (I
> > > believe
> > > > > > these
> > > > > > > > are
> > > > > > > > > > > > true..correct me if I'm wrong):
> > > > > > > > > > > >
> > > > > > > > > > > >    - If configs are modified in
the management UI or
> > the
> > > > > > Stellar
> > > > > > > > REPL
> > > > > > > > > > and
> > > > > > > > > > > >    someone forgets to pull the
configs from zookeeper
> > to
> > > > > disk,
> > > > > > > > before
> > > > > > > > > > > they
> > > > > > > > > > > > do
> > > > > > > > > > > >    a push via zk_load_utils, they
will clobber the
> > > configs
> > > > in
> > > > > > > > > zookeeper
> > > > > > > > > > > > with
> > > > > > > > > > > >    old configs.
> > > > > > > > > > > >    - If the global config is changed
on disk and the
> > > ambari
> > > > > > > service
> > > > > > > > > > > >    restarts, it'll get reset with
the original global
> > > > config.
> > > > > > > > > > > >    - *Ryan, in the management
UI, if someone changes
> > the
> > > > > > > zookeeper
> > > > > > > > > > > configs
> > > > > > > > > > > >    from outside, are those configs
reflected
> > immediately
> > > in
> > > > > the
> > > > > > > > UI?*
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > It seems to me that we have a
couple of options here:
> > > > > > > > > > > >
> > > > > > > > > > > >    - A service to intermediate
and handle config
> > > > > > update/retrieval
> > > > > > > > and
> > > > > > > > > > > >    tracking historical changes
so these different
> > > > mechanisms
> > > > > > can
> > > > > > > > use
> > > > > > > > > a
> > > > > > > > > > > > common
> > > > > > > > > > > >    component for config management/tracking
and
> > refactor
> > > > the
> > > > > > > > existing
> > > > > > > > > > > >    mechanisms to use that service
> > > > > > > > > > > >    - Standardize on exactly one
component to manage
> the
> > > > > configs
> > > > > > > and
> > > > > > > > > > > regress
> > > > > > > > > > > >    the others (that's a verb,
right?   nicer than
> > > delete.)
> > > > > > > > > > > >
> > > > > > > > > > > > I happen to like the service approach,
myself, but I
> > > wanted
> > > > > to
> > > > > > > put
> > > > > > > > it
> > > > > > > > > > up
> > > > > > > > > > > > for discussion and hopefully someone
will volunteer
> to
> > > > design
> > > > > > > such
> > > > > > > > a
> > > > > > > > > > > thing.
> > > > > > > > > > > >
> > > > > > > > > > > > To frame the debate, I want us
to keep in mind a
> couple
> > > of
> > > > > > things
> > > > > > > > > that
> > > > > > > > > > > may
> > > > > > > > > > > > or may not be relevant to the
discussion:
> > > > > > > > > > > >
> > > > > > > > > > > >    - We will eventually be moving
to support kerberos
> > so
> > > > > there
> > > > > > > > should
> > > > > > > > > > at
> > > > > > > > > > > >    least be a path to use kerberos
for any solution
> IMO
> > > > > > > > > > > >    - There is value in each of
the different
> mechanisms
> > > in
> > > > > > place
> > > > > > > > now.
> > > > > > > > > > If
> > > > > > > > > > > >    there weren't, then they wouldn't
have been
> created.
> > > > > Before
> > > > > > > we
> > > > > > > > > try
> > > > > > > > > > to
> > > > > > > > > > > > make
> > > > > > > > > > > >    this a "there can be only one"
argument, I'd like
> to
> > > > hear
> > > > > > very
> > > > > > > > > good
> > > > > > > > > > > >    arguments.
> > > > > > > > > > > >
> > > > > > > > > > > > Finally, I'd appreciate if some
people might answer
> the
> > > > > > > questions I
> > > > > > > > > > have
> > > > > > > > > > > in
> > > > > > > > > > > > bold there.  Hopefully this discussion,
if nothing
> else
> > > > > > happens,
> > > > > > > > will
> > > > > > > > > > > > result in fodder for proper documentation
of the ins
> > and
> > > > outs
> > > > > > of
> > > > > > > > each
> > > > > > > > > > of
> > > > > > > > > > > > the components bulleted above.
> > > > > > > > > > > >
> > > > > > > > > > > > Best,
> > > > > > > > > > > >
> > > > > > > > > > > > Casey
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > --
> > > > > > > > > > > Nick Allen <nick@nickallen.org>
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Nick Allen <nick@nickallen.org>
> > > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Nick Allen <nick@nickallen.org>
> > > >
> > >
> >
>



-- 
Nick Allen <nick@nickallen.org>

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