incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jonathan Ellis <jbel...@gmail.com>
Subject Re: memtable_flush_after_mins setting not working
Date Fri, 25 Feb 2011 23:13:17 GMT
Yes.

On Fri, Feb 25, 2011 at 4:29 PM, Jeffrey Wang <jwang@palantir.com> wrote:
> I just noticed this thread. Does this mean that (assuming the same setup of
> an empty keyspace and CFs added later) if I have a CF that I write to for
> some time, but not enough to hit the flush limits, it will never get flushed
> until the server is restarted? I believe this is causing commit logs to not
> be deleted, which is taking up a ton of disk space (in addition to a bunch
> of small memtables being stuck in memory).
>
>
>
> -Jeffrey
>
>
>
> From: Ching-Cheng Chen [mailto:cchen@evidentsoftware.com]
> Sent: Thursday, February 17, 2011 8:52 AM
> To: user@cassandra.apache.org
> Cc: Jonathan Ellis
> Subject: Re: memtable_flush_after_mins setting not working
>
>
>
> https://issues.apache.org/jira/browse/CASSANDRA-2183
>
>
>
> Regards,
>
>
>
> Chen
>
>
>
> www.evidentsoftware.com
>
> On Thu, Feb 17, 2011 at 11:47 AM, Ching-Cheng Chen
> <cchen@evidentsoftware.com> wrote:
>
> Certainly, I'll open a ticket to track this issue.
>
>
>
> Regards,
>
>
>
> Chen
>
>
>
> www.evidentsoftware.com
>
>
>
> On Thu, Feb 17, 2011 at 11:42 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>
> Your analysis sounds correct to me.  Can you open a ticket on
> https://issues.apache.org/jira/browse/CASSANDRA ?
>
> On Thu, Feb 17, 2011 at 10:17 AM, Ching-Cheng Chen
> <cchen@evidentsoftware.com> wrote:
>> We have observed the behavior that memtable_flush_after_mins setting not
>> working occasionally.   After some testing and code digging, we finally
>> figured out what going on.
>> The memtable_flush_after_mins won't work on certain condition with current
>> implementation in Cassandra.
>>
>> In org.apache.cassandra.db.Table,  the scheduled flush task is setup by
>> the
>> following code during construction.
>>
>> int minCheckMs = Integer.MAX_VALUE;
>>
>> for (ColumnFamilyStore cfs : columnFamilyStores.values())
>> {
>>     minCheckMs = Math.min(minCheckMs, cfs.getMemtableFlushAfterMins() * 60
>> *
>> 1000);
>> }
>> Runnable runnable = new Runnable()
>> {
>>    public void run()
>>    {
>>        for (ColumnFamilyStore cfs : columnFamilyStores.values())
>>        {
>>            cfs.forceFlushIfExpired();
>>        }
>>    }
>> };
>> flushTask = StorageService.scheduledTasks.scheduleWithFixedDelay(runnable,
>> minCheckMs, minCheckMs, TimeUnit.MILLISECONDS);
>>
>> Now for our application, we will create a keyspacewithout any columnfamily
>> first.  And only add needed columnfamily later depends on request.
>> However, when keyspacegot created (without any columnfamily ), the above
>> code will actually schedule a fixed delay flush check task with
>> Integer.MAX_VALUE ms
>> since there is no columnfamily yet.
>> Later when you add columnfamily to this empty keyspace, the initCf()
>> method
>> in Table.java doesn't check whether the scheduled flush check task
>> interval
>> need
>> to be updated or not.   To fix this, we'd need to restart the Cassandra
>> after columnfamily added into the keyspace.
>> I would suggest that add additional logic in initCf() method to recreate a
>> scheduled flush check task if needed.
>> Regards,
>> Chen
>> www.evidentsoftware.com
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com
>
> --
> www.evidentsoftware.com
>
>



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support
http://www.datastax.com

Mime
View raw message