WebCamp Zagreb 2014, Cassandra, web scale no sql data platform presentation by Marko Švaljek.

1. CASSANDRA
WEB-SCALE NOSQL DATA PLATFORM
Marko Švaljek / @msvaljek
0

2. ABOUT ME
Software Developer at Kapsch
Zagreb Cassandra Meetup

3. NUMBERS
25% of the Fortune 100 use it
Apple - 75 000 nodes, 10 PB of data
Netflix - 2500 nodes, 1 trillion req/day
DataStax - professional Cassandra support
Meetup - 167 Groups, 114 Cities, 41 Countries

4. FUN PART
Android TV Box
Arduino

5. FUN PART
Android TV Box
Arduino

6. BREWER'S CAP THEOREM
Availability
nodes can fail
CA AP
RDBMS Cassandra
Consistency Partition Tolerance
CP
same data for all network fails
MongoDB

7. CONSISTENT HASHING - 1
hash_function: row_key -> [0 .. 99]
A
D
0
C B
25
50
75

8. CONSISTENT HASHING - 2
Murmur3: row_key -> -263 to 263-1
A
B C
D
hash(C")
hash(A")
hash(D")
hash(B")

9. CONSISTENT HASHING - 3
num_tokens: 256
virtual nodes

10. GOSSIP
A
H B
C
D
F
E is down
G is down
1
2
3

11. CLIENT REQUESTS
A
Client D B
C
Coordinator
Node
quorum =
replication_factor
2
+ 1

12. WRITE PATH
Memory
Disk
Commit log
memtable
Data
memtable
SSTable
Flush
Index

13. COMPACTION
Latest data entries
Remove
tombstones
- - - - - - - - - -
- - - - - - - - - -
- - - - - - - - - -
Merge
Uncompacted data
- - - - -
- - - - -
- - - - -
- - - - -
- - - - -
Compacted data
- - - - -
Consolidate

14. BLOOM FILTER
A B C
1 1 1 0 1 1 0 0 0 1 0 1
✓ ✓ ✗
D

15. READING FROM SSTABLE
Data?
Memory
Disk
Read Bloom Filter
Data not in filter Data is in filter
Key Cache
SSTable Data

16. DATA ORGANIZATION
Keyspace
Column family (table)
Column Column
Row Value Value
...
Timpestamp Timpestamp

17. KEYSPACE
CREATE KEYSPACE used_cars
WITH replication = {
'class': 'SimpleStrategy',
'replication_factor' : 1};
CREATE KEYSPACE used_cars
WITH replication = {
'class': 'NetworkTopologyStrategy',
'DC1' : 1,
'DC2' : 3};

18. TABLES
CREATE TABLE users (
username text PRIMARY KEY,
password text,
first_name text,
last_name text,
state text
);

19. INSERTING
INSERT INTO
offers (username, date, price,
brand, model, year, mileage, color)
VALUES ('jsmith', '2014-09-19 11:35:20', 6000,
'BMW', '120i', 2010, 40000, 'Black');

20. UPDATE
UPDATE offers SET
brand = 'Ford',
model = 'Mustang'
WHERE
username = 'jdoe'
AND date = '2014-08-11 17:12:32+0200';
Use upsert (insert same data) when possible
NO updating of primary key fields

21. DELETE
DELETE FROM offers
WHERE username = 'jdoe'
AND date = '2014-08-11 17:12:32+0200';
tombstones

22. SELECT
SELECT username, date, brand, model
FROM offers
WHERE username = 'jsmith';
username | date | brand | model
----------+--------------------------+-------+-------
jsmith | 2014-05-11 01:22:11+0200 | Ford | Orion
jsmith | 2014-09-09 11:35:20+0200 | BMW | 118d
jsmith | 2014-09-19 11:35:20+0200 | BMW | 120i
jsmith | 2014-09-20 17:12:32+0200 | Audi | A6

23. APPS
15+ languages supported
var cql = require('node-cassandra-cql');
var client = new cql.Client({
hosts: ['127.0.0.1:9042'],
keyspace: 'test'
});
client.execute('SELECT * FROM test_table', [],
function(err, result) {
for (var i = 0; i < result.rows.length; i++) {
console.log(result.rows[i].get('id'));
console.log(result.rows[i].get('test_value'));
}
}
);

24. THANK YOU!
Q & A
@msvaljek