Cassandra: How to tell where the data resides and on which nodes.

 

cqlsh:linkedin> select * from location;

 vehicle_id | date       | time                            | latitude | longtitude

------------+------------+---------------------------------+----------+------------

   ME100AAS | 2014-05-19 | 2014-05-19 08:50:00.000000+0000 | 44.74941 |   -67.2507

   ME100AAS | 2014-05-19 | 2014-05-19 08:40:00.000000+0000 | 44.74648 |  -67.26444

   ME100AAS | 2014-05-19 | 2014-05-19 08:30:00.000000+0000 | 44.74258 |  -67.34272

   ME100AAS | 2014-05-19 | 2014-05-19 08:20:00.000000+0000 | 44.72795 |  -67.40177

   ME100AAS | 2014-05-19 | 2014-05-19 08:10:00.000000+0000 | 44.69965 |  -67.47043

   ME100AAS | 2014-05-19 | 2014-05-19 08:00:00.000000+0000 | 44.61909 |   -67.8462

   WA063JXD | 2014-05-19 | 2014-05-19 08:50:00.000000+0000 | 47.70144 | -117.01791

   WA063JXD | 2014-05-19 | 2014-05-19 08:40:00.000000+0000 | 47.69589 | -117.04126

   WA063JXD | 2014-05-19 | 2014-05-19 08:30:00.000000+0000 | 47.68711 |  -117.0701

   WA063JXD | 2014-05-19 | 2014-05-19 08:20:00.000000+0000 | 47.68017 | -117.08932

   WA063JXD | 2014-05-19 | 2014-05-19 08:10:00.000000+0000 | 47.67093 | -117.10924

   WA063JXD | 2014-05-19 | 2014-05-19 08:00:00.000000+0000 | 47.67547 | -117.23619

  CA6AFL218 | 2014-05-19 | 2014-05-19 08:50:00.000000+0000 | 36.11959 | -115.17258

  CA6AFL218 | 2014-05-19 | 2014-05-19 08:40:00.000000+0000 | 36.04423 | -115.18112

  CA6AFL218 | 2014-05-19 | 2014-05-19 08:30:00.000000+0000 | 35.91153 | -115.20631

  CA6AFL218 | 2014-05-19 | 2014-05-19 08:20:00.000000+0000 | 35.88326 | -115.22528

  CA6AFL218 | 2014-05-19 | 2014-05-19 08:10:00.000000+0000 | 35.76301 | -115.33514

  CA6AFL218 | 2014-05-19 | 2014-05-19 08:00:00.000000+0000 | 35.69166 |  -115.3681

cqlsh:linkedin> desc table location

CREATE TABLE linkedin.location (

vehicle_id text,

date text,

time timestamp,

latitude double,

longtitude double,

PRIMARY KEY ((vehicle_id, date), time)

) WITH CLUSTERING ORDER BY (time DESC)

AND additional_write_policy = '99p'

AND bloom_filter_fp_chance = 0.01

AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}

AND cdc = false

AND comment = ''

AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}

AND compression = {'chunk_length_in_kb': '16', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}

AND memtable = 'default'

AND crc_check_chance = 1.0

AND default_time_to_live = 0

AND extensions = {}

AND gc_grace_seconds = 864000

AND max_index_interval = 2048

AND memtable_flush_period_in_ms = 0

AND min_index_interval = 128

AND read_repair = 'BLOCKING'

AND speculative_retry = '99p';

Provide the token function with the compound keys. Compound keys are hashed and stored in corresponding nodes.

cqlsh:linkedin> select token(vehicle_id,date) from location;

system.token(vehicle_id, date)

--------------------------------

-7657837382140274291

-7657837382140274291

-7657837382140274291

-7657837382140274291

-7657837382140274291

-7657837382140274291

7624412873298128873

7624412873298128873

7624412873298128873

7624412873298128873

7624412873298128873

7624412873298128873

8294848196898204914

8294848196898204914

8294848196898204914

8294848196898204914

8294848196898204914

8294848196898204914

(18 rows)

Use nodetool getendpoint function to figure out where they reside.

cassandra@cassandra02:/var/log/cassandra$ nodetool getendpoints linkedin location '8294848196898204914'

192.168.1.35

cassandra@cassandra02:/var/log/cassandra$ nodetool getendpoints linkedin location '-7657837382140274291'

192.168.1.32