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 <ceste...@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 <n...@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 <ma...@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.miklav...@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 <ceste...@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 <n...@nickallen.org> > > >
