-Re: default configs
Joe Stein 2013-01-18, 21:58
how about a command line script (bin/kafka-config-init.sh) to load in a
file for the configs to initialize the config values in zookeerper but
kafka reads the configs from zookeeper
another script can also have options for doing updates
if we provide a writing mechanism then the config management systems (we
use chef) can interact nice the zookeeper updates in a standard way that we
document and support
On Fri, Jan 18, 2013 at 4:19 PM, Jay Kreps <[EMAIL PROTECTED]> wrote:
> Yes please, any help very much appreciated.
> I am not sure if I understand what you are proposing, though. Are you
> saying support both the config file and zk for topic-level configs? I hate
> to do things where the answer is "do both"...I guess I feel that although
> everyone walks away happy it ends up being a lot of code and combinatorial
> testing. So if there is a different plan that hits all requirements I like
> that better. I am very sensitive to the fact that zookeeper is an okay
> key/value store but a really poor replacement for a config management
> system. It might be worth while to try to work out a way that meets all
> needs, if such a thing exists.
> Is bouncing brokers for topic-overrides a problem for you in your
> environment? If so how would you fix it?
> On Fri, Jan 18, 2013 at 7:53 AM, Joe Stein <[EMAIL PROTECTED]>
> > Can I help out?
> > Also can we abstract the config call too? We have so much in chef, it's
> > not that i don't want to call our zookeeper cluster for it but we don't
> > have our topology yet mapped out in znodes they are in our own instances
> > code.
> > It should have both a pull and push for changes, one thing that's nice
> > with zookeeper and having a watcher.
> > /*
> > Joe Stein, Chief Architect
> > http://www.medialets.com
> > Twitter: @allthingshadoop
> > Mobile: 917-597-9771
> > */
> > On Jan 18, 2013, at 12:09 AM, Jay Kreps <[EMAIL PROTECTED]> wrote:
> > > Currently kafka broker config is all statically defined in a properties
> > > file with the broker. This mostly works pretty well, but for per-topic
> > > configuration (the flush policy, partition count, etc) it is pretty
> > painful
> > > to have to bounce the broker every time you make a config change.
> > >
> > > That lead to this proposal:
> > > https://cwiki.apache.org/confluence/display/KAFKA/Dynamic+Topic+Config
> > >
> > > An open question is how topic-default configurations should work.
> > >
> > > Currently each of our topic-level configs is paired with a default. So
> > you
> > > would have something like
> > > segment.size.bytes
> > > which would be the default, and then you can override this for topics
> > that
> > > need something different using a map:
> > > segment.size.bytes.per.topic
> > >
> > > The proposal is to move the topic configuration into zookeeper so that
> > for
> > > a topic "my-topic" we would have a znode
> > > /brokers/topics/my-topic/config
> > > and the contents of this znode would be the topic configuration either
> > > json or properties or whatever.
> > >
> > > There are two ways this config could work:
> > > 1. Defaults resolved at topic creation time: At the time a topic is
> > created
> > > the user would specify some properties they wanted for that topic, any
> > > topic they didn't specify would take the server default. ALL these
> > > properties would be stored in the znode.
> > > 2. Defaults resolved at config read time: When a topic is created the
> > user
> > > specifies particularly properties they want and ONLY the properties
> > > particularly specify would be stored. At runtime we would merge these
> > > properties with whatever the server defaults currently are.
> > >
> > > This is a somewhat nuanced point, but perhaps important.
> > >
> > > The advantage of the first proposal is that it is simple. If you want
> > > know the configuration for a particular topic you go to zookeeper and
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