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From "Thakrar, Jayesh" <>
Subject Re: Effect of frequent mutations / memtable
Date Thu, 25 May 2017 20:46:27 GMT
That's because Zookeeper is purpose built for such a kind of usage.
Its asynchronous nature  - e.g. you can create "watchers" with callbacks so that when ephemeral
nodes die/disappear (due to servers crashing) makes it better to program.
It also reduces the "checkin" and "polling" cycle overhead.
Furthermore, zk does not have the "overhead" of other things that Cassandra does.

Honestly I am not familiar with Paxos and stuff, so can't speak to it.

On 5/25/17, 3:40 PM, "Jan Algermissen" <> wrote:

    Hi Jayesh,
    On 25 May 2017, at 18:31, Thakrar, Jayesh wrote:
    > Hi Jan,
    > I would suggest looking at using Zookeeper for such a usecase.
    thanks - yes, it is an alternative.
    Out of curiosity: since both, Zk and C* implement Paxos to enable such 
    kind of thing, why do you think Zookeeper would be a better fit?
    > See for some 
    > examples.
    > Zookeeper is used for such purposes in Apache HBase (active master), 
    > Apache Kafka (active controller), Apache Hadoop, etc.
    > Look for the "Leader Election" usecase.
    > Examples
    > Its more/new work, but should be an elegant solution.
    > Hope that helps.
    > Jayesh
    > On 5/25/17, 9:19 AM, "Jan Algermissen" <> 
    > wrote:
    >     Hi,
    >     I am using a updates to a column with a ttl to represent a lock. 
    > The
    >     owning process keeps updating the lock's TTL as long as it is 
    > running.
    >     If the process crashes, the lock will timeout and be deleted. Then
    >     another process can take over.
    >     I have used this pattern very successfully over years with TTLs in 
    > the
    >     order of tens of seconds.
    >     Now I have a use case in mind that would require much smaller 
    > TTLs, e.g.
    >     1 or two seconds and I am worried about the increased number of
    >     mutations and possible effect on SSTables.
    >     However: I'd assume these frequent updates on a cell to mostly 
    > happen in
    >     the memtable resulting in only occasional manifestation in 
    > SSTables.
    >     Is that assumption correct and if so, what config parameters 
    > should I
    >     tweak to keep the memtable from being flushed for longer periods 
    > of
    >     time?
    >     Jan

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