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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: Timeout reading row from CF with collections
Date Fri, 12 Jul 2013 08:20:12 GMT
My bet is that you're hitting
https://issues.apache.org/jira/browse/CASSANDRA-5677.

--
Sylvain


On Fri, Jul 12, 2013 at 8:17 AM, Paul Ingalls <paulingalls@gmail.com> wrote:

> I'm running into a problem trying to read data from a column family that
> includes a number of collections.
>
> Cluster details:
> 4 nodes running 1.2.6 on VMs with 4 cpus and 7 Gb of ram.
> raid 0 striped across 4 disks for the data and logs
> each node has about 500 MB of data currently loaded
>
> Here is the schema:
>
> create table user_scores
> (
> user_id varchar,
> post_type varchar,
> score double,
> team_to_score_map map<varchar, double>,
> affiliation_to_score_map map<varchar, double>,
> campaign_to_score_map map<varchar, double>,
> person_to_score_map map<varchar, double>,
> primary key(user_id, post_type)
> )
> with compaction =
> {
>   'class' : 'LeveledCompactionStrategy',
>   'sstable_size_in_mb' : 10
> };
>
> I used the leveled compaction strategy as I thought it would help with
> read latency…
>
> Here is a trace of a simple select against the cluster when it had nothing
> else was reading or writing (cpu was < 2%):
>
>  activity                                                                |
> timestamp    | source         | source_elapsed
>
> -------------------------------------------------------------------------+--------------+----------------+----------------
>                                                       execute_cql3_query |
> 05:51:34,557 |  100.69.176.51 |              0
>                                     Message received from /100.69.176.51| 05:51:34,195
| 100.69.184.134 |            102
>                          Executing single-partition query on user_scores |
> 05:51:34,199 | 100.69.184.134 |           3512
>                                             Acquiring sstable references |
> 05:51:34,199 | 100.69.184.134 |           3741
>                                              Merging memtable tombstones |
> 05:51:34,199 | 100.69.184.134 |           3890
>                                              Key cache hit for sstable 5 |
> 05:51:34,199 | 100.69.184.134 |           4040
>                              Seeking to partition beginning in data file |
> 05:51:34,199 | 100.69.184.134 |           4059
>                               Merging data from memtables and 1 sstables |
> 05:51:34,200 | 100.69.184.134 |           4412
>  Parsing select * from user_scores where user_id='26257166' LIMIT 10000; |
> 05:51:34,558 |  100.69.176.51 |             91
>                                                       Peparing statement |
> 05:51:34,558 |  100.69.176.51 |            238
>                                Enqueuing data request to /100.69.184.134| 05:51:34,558
|  100.69.176.51 |            567
>                                       Sending message to /100.69.184.134| 05:51:34,558
|  100.69.176.51 |            979
>                                                         Request complete |
> 05:51:54,562 |  100.69.176.51 |       20005209
>
> You can see that I increased the timeout and it still fails.  This seems
> to happen with rows that have maps with a larger number of entries.  It is
> very reproducible with my current data set.
>
> Any ideas on why I can't query for a row?
>
> Thanks!
>
> Paul
>
>
>

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