I am returning to the ZooKeeper land after a long hiatus, so got some questions :-)

I am running some tests trying to reduce the frequency of ZK snapshots. So I am setting zookeeper.snapCount to a very high value (10 million transactions) so that it forces ZK to create snapshots infrequently. ZK seems to be ignoring this completely and creating snapshots once about 72K transactions (I thought the default snapCount value is 100K). I have the following line in the config file:

zookeeper.snapCount=10000000

Couple of questions:

1. Any idea why ZK is not honoring the snapCount value? Any idea why it is not honoring the default value either?
2. If I understand it correctly, the transaction log is reset each time (and only when) a snapshot is taken. If snapshots are not taken regularly, the transaction log will keep growing in size without ever being truncated to shrink it's size. Did I describe this right?

Thanks
Raghu

The logic that controls rolling the logs and taking a snap is:
randRoll = random next in between 0 and snapCount/2
if we've logged  more than snapCount/2 + randRoll, create a new randRoll
and take a snapshot.

So creating a snapshot after ~72K transactions indicates to me that you
probably got the default 100K for the snapCount. Not sure why it didn't get
read, though, ZooKeeperServer does a
System.getProperty("zookeeper.snapCount") and parses that int for the
snapCount, defaulting to 100000 if it fails. Possibly just a formatting
issue in your configs?
Yes, if you don't snapshot regularly, the transaction log will keep growing
in size and only get rolled when it is time to do a snapshot.

C
On Wed, Feb 13, 2013 at 10:09 PM, Raghu Shastry <[EMAIL PROTECTED]> wrote:

> I am returning to the ZooKeeper land after a long hiatus, so got
> some questions :-)
>
> I am running some tests trying to reduce the frequency of ZK snapshots. So
> I am setting zookeeper.snapCount to a very high value (10
> million transactions) so that it forces ZK to create snapshots
> infrequently. ZK seems to be ignoring this completely and creating
> snapshots once about 72K transactions (I thought the default snapCount
> value is 100K). I have the following line in the config file:
>
> zookeeper.snapCount=10000000
>
> Couple of questions:
>
> 1. Any idea why ZK is not honoring the snapCount value? Any idea why it is
> not honoring the default value either?
> 2. If I understand it correctly, the transaction log is reset each time
> (and only when) a snapshot is taken. If snapshots are not taken regularly,
> the transaction log will keep growing in size without ever being truncated
> to shrink it's size. Did I describe this right?
>
> Thanks
> Raghu