Sunday, May 5, 2013

Friday, April 19, 2013

My Note on Solutions.: Cassandra DSE, Testing Solr integration

My Note on Solutions.: Cassandra DSE, Testing Solr integration

everything worked for me also, except i got 
an error on the Solr search UI when querying saying"HTTP Status 500 - Unavailible shards"
 i had to do a 
'update keyspace WITH placement_strategy = 'NetworkTopologyStrategy' and strategy_options=[{Solr:1}]; ' 

 to make things work ..

 Anybody knows how to index data directly in Solr that is *not* first entered/created in Cassandra ? 
It seems like it is possible : " If you HTTP post the files to a non-existing column keyspace or column family, DSE Search creates the keyspace and column family, and then starts indexing the data. F"
from http://www.datastax.com/docs/datastax_enterprise2.0/search/dse_search_about

Monday, April 15, 2013

Using secondary indexes in Cassandra CQL: need to use an indexed column in your query

Say, i create this table:

cqlsh:Keyspace2> CREATE TABLE users (   user_name varchar PRIMARY KEY,   password varchar,   gender varchar,   session_token varchar,   state varchar,   birth_year bigint );
cqlsh:Keyspace2> INSERT INTO users
             ...          (user_name, password)
             ...          VALUES ('jsmith', 'ch@ngem3a');
cqlsh:Keyspace2> INSERT INTO users          (user_name, password)          VALUES ('jsmith2', 'ch@ngem3a2');
cqlsh:Keyspace2> create index on users (password);
I can create an index and query:

cqlsh:Keyspace2> select * from users where password = 'ch@ngem3a2' and user_name = 'jsmith2';
 user_name | birth_year | gender | password   | session_token | state
-----------+------------+--------+------------+---------------+-------
   jsmith2 |       1963 |   null | ch@ngem3a2 |          null |  null

 but this doesnt work:
cqlsh:Keyspace2> select * from users where birth_year > 1960;
Bad Request: No indexed columns present in by-columns clause with Equal operator
Perhaps you meant to use CQL 2? Try using the -2 option when starting cqlsh.
cqlsh:Keyspace2> select * from users where birth_year > 1960 and user_name 'jsmith';
Bad Request: line 1:48 no viable alternative at input 'user_name'
cqlsh:Keyspace2> select * from users where birth_year > 1960 and user_name = 'jsmith';
Bad Request: No indexed columns present in by-columns clause with Equal operator
Perhaps you meant to use CQL 2? Try using the -2 option when starting cqlsh.

Unless i use an indexed column in the query (not necessarily the primary indexed one):

cqlsh:Keyspace2> select * from users where birth_year > 1960  and password = 'ch@ngem3a2';
 user_name | birth_year | gender | password   | session_token | state
-----------+------------+--------+------------+---------------+-------
   jsmith2 |       1963 |   null | ch@ngem3a2 |          null |  null 

Trying Cassandra CQL

Here is how to create a new column on the fly in Cassandra's CQL2:


cqlsh:Keyspace2> select * from users;
 user_name | birth_year | gender | password   | session_token | state
-----------+------------+--------+------------+---------------+-------
   jsmith3 |       null |   null |        200 |          null |  null
    jsmith |       1968 |   null |  ch@ngem3a |          null |  null
   jsmith2 |       1963 |   null | ch@ngem3a2 |          null |  null

cqlsh:Keyspace1> insert into users (KEY, x) values ('jsmith',100);
cqlsh:Keyspace1> select * from users;
 KEY,TEST | birth_year,1968 | gender,m
 KEY,TEST1 | birth_year,1968 | gender,f
 KEY,jsmith | x,100



Thursday, April 4, 2013

How to test Cassandra

Datastax's Cassandra comes with a stress tester, that can generate data for you.
It is all built in with different kind of parameters.
Here i am generating 1 M rows with 10 columns, readable, random values (up to 1000 values) that are indexed:

cassandra-stress -o INSERT  -n 1000000 -c 10 -U UTF8Type  -C 1000 --create-index=KEYS -r

Wednesday, April 3, 2013

How to use a Hive Avro Serde in distributed mode

Lately with our team, we tried to optimize our data by using an Avro Serde (with a binary encoding).
Unfortunately on CDH4, we would run into errors after creating the table;
Here is the Hive schema that we used:

Create external table avro_test 
ROW FORMAT SERDE
'org.apache.hadoop.hive.serde2.avro.AvroSerDe'
 STORED AS INPUTFORMAT
'org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat' 
OUTPUTFORMAT
'org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat' 
LOCATION
'/kafka/avro/topic_avro2/hourly/<date>/' TBLPROPERTIES ( 
'avro.schema.url'='file:///home/ubuntu/Message.avsc') ; 

But this didn't work :

hive>
    > select count(*) from avro_test;
Total MapReduce jobs = 1
Launching Job 1 out of 1
Number of reduce tasks determined at compile time: 1
In order to change the average load for a reducer (in bytes):
  set hive.exec.reducers.bytes.per.reducer=<number>
In order to limit the maximum number of reducers:
  set hive.exec.reducers.max=<number>
In order to set a constant number of reducers:
  set mapred.reduce.tasks=<number>
Starting Job = job_201303291126_0045, Tracking URL = ..Kill Command = /home/ubuntu/cdh4/hadoop-2.0.0-mr1-cdh4.2.0/bin/hadoop job  -kill job_201303291126_0045
Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 1
2013-03-29 20:50:47,871 Stage-1 map = 0%,  reduce = 0%
2013-03-29 20:51:22,151 Stage-1 map = 100%,  reduce = 100%
Ended Job = job_201303291126_0045 with errors
Error during job, obtaining debugging information...
Job Tracking URL: ..Examining task ID: task_201303291126_0045_m_000002 (and more) from job job_201303291126_0045
Task with the most failures(4):
-----
Task ID:
  task_201303291126_0045_m_000000
URL:..
-----
Diagnostic Messages for this Task:
java.io.IOException: java.lang.reflect.InvocationTargetExceptionat org.apache.hadoop.hive.io.HiveIOExceptionHandlerChain.handleRecordReaderCreationException(HiveIOExceptionHandlerChain.java:97)
at org.apache.hadoop.hive.io.HiveIOExceptionHandlerUtil.handleRecordReaderCreationException(HiveIOExceptionHandlerUtil.java:57)
at org.apache.hadoop.hive.shims.HadoopShimsSecure$CombineFileRecordReader.initNextRecordReader(HadoopShimsSecure.java:369)
at org.apache.hadoop.hive.shims.HadoopShimsSecure$CombineFileRecordReader.<init>(HadoopShimsSecure.java:316)
at org.apache.hadoop.hive.shims.HadoopShimsSecure$CombineFileInputFormatShim.getRecordReader(HadoopShimsSecure.java:430)
at org.apache.hadoop.hive.ql.io.CombineHiveInputFormat.getRecordReader(CombineHiveInputFormat.java:540)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:395)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:333)
at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
at java.security.AccessController.doPrivileged(Native 
Well apparently the fix is to provide an inline schema instead:
CREATE EXTERNAL TABLE avro_topic
ROW FORMAT SERDE
'org.apache.hadoop.hive.serde2.avro.AvroSerDe'
STORED AS INPUTFORMAT
'org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat'
OUTPUTFORMAT
'org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat'
 LOCATION 
'/kafka/avro/topic_avro/hourly/2013/04/01/06'
TBLPROPERTIES (
'avro.schema.literal'='{
"namespace": "com.test.beans",
"type": "record",
"name": "Message",
"doc": "Logs for not so important stuff.",
"fields": [
{
"name": "id",
"type": "long",
"default":0
},
{
"name": "logTime",
"type": "long",
"default":0
},
{
"name": "muchoStuff",
"type": {"type": "map", "values": "string"},
"default":null
}
]
}');

How to recover from errors in Hive interactive mode

Lately, working with a team offshore on the same instance of Hive, I would get errors like:


hive> show tables;
FAILED: Error in metadata: java.lang.RuntimeException: Unable to instantiate org.apache.hadoop.hive.metastore.HiveMetaStoreClient
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask
hive> select count(*) from json_topic1;                                                                                                         FAILED: SemanticException Unable to fetch table json_topic1          
hive> 


I was told that generally we get this exception if we  the hive console not terminated properly. 
The fix:

Run the jps command, look for "RunJar" process and kill it using 
kill -9 <RunJarprocessId> command