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Kafka >> mail # user >> Keeping zookeeper happy?


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Re: Keeping zookeeper happy?
Here are some comments from Dave. He'll be adding some more details to a
blog post that we can link from that wiki.

For the most part, yes, it is pretty much the obvious, but here's the
short version of some longer details that I really should get into the
wiki that you pointed at:
- Redundancy in the physical/hardware/network layout: try not to put
  them all in the same rack, decent (but don't go nuts) hardware, try to
  keep redundant power and network paths, etc
- I/O segregation: if you do a lot of write type traffic you'll almost
  definitely want the transaction logs on a different disk group than
  app logs and snapshots (the write to the zookeeper service has a
  synchronous write to disk, which can be slow).
- Application segregation: Unless you really understand the application
  patterns of other apps that you want to install on the same box, it
  can be a good idea to run zookeeper in isolation (though this can be a
  balancing act with the capabilities of the hardware).
- Use care with virtualization: It can work, depending on your cluster
  layout and read/write patterns and SLAs, but the tiny overheads
  introduced by the virtualization layer can add up and throw off
  zookeeper, as it can be very time sensitive
- Zookeeper configuration and monitoring: It's java, make sure you give
  it 'enough' heap space (I usually run them with 3-5G, but that's
  mostly due to the data set size we have here).  Unfortunately I don't
  have a good formula for it. As far as monitoring, both JMZ and the 4
  letter commands are very useful, they do overlap in some cases (and in
  those cases I prefer the 4 letter commands, they seem more
  predictable, or at the very least, they work better with the LI
  monitoring infrastructure)
- Don't overbuild the cluster: large clusters, especially in a write
  heavy usage pattern, means a lot of intra cluster communication
  (quorums on the writes and subsequent cluster member updates), but
  don't underbuild it (and risk swamping the cluster).

Overall, I try to keep the zookeeper system as small as will handle the
load (plus standard growth capacity planning) and as simple as possible.
I try not to do anything fancy with the configuration or application
layout as compared to the official release as well as keep it as self
contained as possible.  For these reasons, I tend to skip the OS
packaged versions, since it has a tendency to try to put things in the
OS standard hierarchy, which can be 'messy', for want of a better way to
word it.
On Tue, Aug 7, 2012 at 12:00 PM, James A. Robinson <
[EMAIL PROTECTED]> wrote:

> Hi folks,
>
> The operations wiki page
>
>   https://cwiki.apache.org/confluence/display/KAFKA/Operations
>
> states, in part
>
>   Zookeeper
>
>   Zookeeper is essential for the correct operation of Kafka. There are
>   a number of things that must be done to keep zookeeper running
>   happily as we have learned the hard way, hopefully Dave and Neha
>   will add this since I don't know what we did.
>
> I was wondering if anyone on the list had comments on this topic?
>
> Were there things beyond what might be considered obvious, e.g.,
> running at least five nodes on separate machines w/ redundant network
> paths, and so forth?
>
>
> Jim
>
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>