metron-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From David Lyle <dlyle65...@gmail.com>
Subject Re: [DISCUSS] Ambari Metron Configuration Management consequences and call to action
Date Fri, 13 Jan 2017 14:15:16 GMT
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>
> >
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message