-Re: default configs
Joe Stein 2013-01-18, 16:30
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 of 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
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:
> 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
> which would be the default, and then you can override this for topics that
> need something different using a map:
> The proposal is to move the topic configuration into zookeeper so that for
> a topic "my-topic" we would have a znode
> and the contents of this znode would be the topic configuration either as
> 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 they
> 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 to
> know the configuration for a particular topic you go to zookeeper and look
> at that topics config. Mixing the combination of server config and
> zookeeper config dynamically makes it a little harder to figure out what
> the current state of anything is.
> The disadvantage of the first proposal (and the advantage of the second
> proposal) is that making global changes is easier. For example if you want
> to globally lower the retention for all topics, in proposal one you would
> have to iterate over all topics and update the config (this could be done
> automatically with tooling, but under the covers the tool would do this).
> In the second case you would just update the default value.
> Thoughts? If no one cares, I will just pick whatever seems best.