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From Matt Foley <ma...@apache.org>
Subject Re: [DISCUSS] Ambari Metron Configuration Management consequences and call to action
Date Mon, 16 Jan 2017 22:32:14 GMT
I agree, we should get all configs into ZK, and managed by Ambari.

I think, when managed by Ambari, a change to configs would always start with Ambari, not Zookeeper:
a) interact with Ambari (either GUI or API) to mutate the configs (starting with current,
or with a historical version from Ambari CM)
b) when finalized in Ambari, Ambari shall push to Zookeeper, and store the new HEAD in Ambari
CM.
With this mechanism in place, there would be no need to “snapshot a config out of Zookeeper
and push it into CM” – it would already be in CM.

The interesting thing not mentioned yet, is that we have to institute security in ZK, so everyone
with access to zkcli can’t change the ZK configs directly.
This is actually a gap that needs to be addressed regardless of our config management approach.

--Matt


On 1/16/17, 1:19 PM, "Casey Stella" <cestella@gmail.com> wrote:

    I presumed that the solution would involve passing kerberos authentication
    tickets to the API calls.  This kind of global context (the
    authorization/authentication bit) is what the Stellar Context was built
    for, in part.  Regardless, I think authorized config updates with reasons
    stored in Ambari is a good thing (TM) and should be the goal.
    
    Casey
    
    On Mon, Jan 16, 2017 at 4:13 PM, David Lyle <dlyle65535@gmail.com> wrote:
    
    > Totally agree with step 1, step 2.
    >
    > That said, we'll have to figure out some method of passing authorization
    > credentials with configuration change requests in order to integrate with
    > Ambari. It will not allow interaction without those (and rightly so, imho).
    > This doesn't affect all Stellar functions, only those that mutate configs.
    > Ambari will require username/password pairs but I think, technology
    > notwithstanding, it's a gotta have. I think it's a bad practise to expose a
    > open endpoint to mutate configs anyway and I would want the ability to
    > audit configuration changes.
    >
    > I don't want to drill too deeply in the implementation, but there are
    > solutions- one easy one would be require authentication to the REPL for
    > functions that mutate the live system.
    >
    > So, perhaps it's a 3 step transition with one step being noodle out how
    > we're going to do access control and audit for configuration?
    >
    > -D...
    >
    >
    > On Mon, Jan 16, 2017 at 3:40 PM, James Sirota <jsirota@apache.org> wrote:
    >
    > > In my view the live configs should live in Zookeeper.  It's basically
    > what
    > > it's designed for.  However, we also have a need for CM of these configs
    > in
    > > case you want to roll back or push a different config set into Zookeeper.
    > > That's what I would use Ambari for...have the ability to take a config
    > out
    > > of CM and push it into Zookeeper...or snapshot a config out of Zookeeper
    > > and push it into CM.  The obvious pre-requisite to having this capability
    > > is to not rely on local storage or HDFS for any config.  So in my mind
    > this
    > > is a 2-step transition.  Step 1 - transition all current configs into
    > > Zookeeper.  Step 2 - integrate config management with Ambari.
    > >
    > > I think passing usernames/passwords to stellar functions is not a
    > feasible
    > > solution at this point
    > >
    > > Thanks,
    > > James
    > >
    > > 15.01.2017, 18:28, "JJ Meyer" <jjmeyer0@gmail.com>:
    > > > Quite late to the party, but with all this great back and forth I felt
    > > like
    > > > I had to join in :)
    > > >
    > > > I believe SolrCloud uses ZooKeeper to manage most of its configuration
    > > > files. When searching, I was only able to find this (
    > > > https://cwiki.apache.org/confluence/display/solr/Using+
    > > ZooKeeper+to+Manage+Configuration+Files).
    > > > I wasn't able to find any initial discussion on their architecture. If
    > we
    > > > can find more we still may be able to learn from them.
    > > >
    > > > Also, on the idea of passing a username/password to a Stellar function
    > or
    > > > to some shell script. We may want to do it a bit differently or at
    > least
    > > > give the option to do it differently. I know supplying the
    > > > username/password directly is easy when testing and playing around, but
    > > it
    > > > probably isn't going to be allowed for a user in production. Maybe we
    > can
    > > > also support a credentials file and eventually support encrypting
    > > sensitive
    > > > values in configs?
    > > >
    > > > Thanks,
    > > > JJ
    > > >
    > > > On Sun, Jan 15, 2017 at 1:26 PM, Michael Miklavcic <
    > > > michael.miklavcic@gmail.com> wrote:
    > > >
    > > >>  Ha, I was betrayed by copy/paste in Chrome.
    > > >>
    > > >>  On Thu, Jan 12, 2017 at 7:24 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
    > >
    > > -------------------
    > > Thank you,
    > >
    > > James Sirota
    > > PPMC- Apache Metron (Incubating)
    > > jsirota AT apache DOT org
    > >
    >
    



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