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From Alex Popescu <al...@datastax.com>
Subject Re: python cql driver - cassandra.ReadTimeout - “Operation timed out - received only 1 responses.”
Date Mon, 02 Jun 2014 21:15:52 GMT
If I'm reading this correctly, what you are seeing is the read_timeout on
Cassandra side and not the client side timeout. Even if you set the client
side timeouts, the C* read & write timeouts are still respected on that
side.


On Mon, Jun 2, 2014 at 10:55 AM, Marcelo Elias Del Valle <
marcelo@s1mbi0se.com.br> wrote:

> I am using Cassandra 2.0 with python CQL.
>
> I have created a column family as follows:
>
> CREATE KEYSPACE IF NOT EXISTS Identification
>   WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy',
>   'DC1' : 1 };
>
> USE Identification;
>
> CREATE TABLE IF NOT EXISTS entitylookup (
>   name varchar,
>   value varchar,
>   entity_id uuid,
>   PRIMARY KEY ((name, value), entity_id))
> WITH
>     caching=all;
>
> I then try to count the number of records in this CF as follows:
>
> #!/usr/bin/env pythonimport argparseimport sysimport tracebackfrom cassandra import ConsistencyLevelfrom
cassandra.cluster import Clusterfrom cassandra.query import SimpleStatement
> def count(host, cf):
>     keyspace = "identification"
>     cluster = Cluster([host], port=9042, control_connection_timeout=600000000)
>     session = cluster.connect(keyspace)
>     session.default_timeout=600000000
>
>     st = SimpleStatement("SELECT count(*) FROM %s" % cf, consistency_level=ConsistencyLevel.ALL)
>     for row in session.execute(st, timeout=600000000):
>         print "count for cf %s = %s " % (cf, str(row))
>     dump_pool.close()
>     dump_pool.join()
> if __name__ == "__main__":
>     parser = argparse.ArgumentParser()
>     parser.add_argument("-cf", "--column-family", default="entitylookup", help="Column
Family to query")
>     parser.add_argument("-H", "--host", default="localhost", help="Cassandra host")
>     args = parser.parse_args()
>
>     count(args.host, args.column_family)
>
>     print "fim"
>
>  The count is not that useful to me, it's just a test with an operation
> that takes long to complete.
>
> Although I have defined timeout as 600000000 seconds, after less than 30
> seconds I get the following error:
>
> ./count_entity_lookup.py  -H localhost -cf entitylookup
>     Traceback (most recent call last):
>       File "./count_entity_lookup.py", line 27, in <module>
>         count(args.host, args.column_family)
>       File "./count_entity_lookup.py", line 16, in count
>         for row in session.execute(st, timeout=None):
>       File "/home/mvalle/pyenv0/local/lib/python2.7/site-packages/cassandra/cluster.py",
line 1026, in execute
>         result = future.result(timeout)
>       File "/home/mvalle/pyenv0/local/lib/python2.7/site-packages/cassandra/cluster.py",
line 2300, in result
>         raise self._final_exception
>     cassandra.ReadTimeout: code=1200 [Timeout during read request] message="Operation
timed out - received only 1 responses." info={'received_responses': 1, 'data_retrieved': True,
'required_responses': 2, 'consistency': 5}
>
>  It seems the answer was found in just a replica, but this really doesn't
> make sense to me. Should't cassandra be able to query it anyway?
>
> These tests are running in a two node cluster, with RF = 2, write and read
> consistency = ALL (but same results using QUORUM).
>
> Thanks in advance.
>
> Best regards,
>
> Marcelo.
>



-- 

:- a)


Alex Popescu
Sen. Product Manager @ DataStax
@al3xandru

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