Cassandra 1.2 Overview

Cassandra 1.2
Jonathan Ellis
Project Chair, Apache Cassandra
CTO, DataStax
@spyced

C* in a nutshell
• Massively scalable
• High performance
• Reliable/Available

©2012 DataStax 2

1.2
• Concurrent schema • Atomic batches
changes
• CQL3
• Virtual nodes • Collections
• “Fat node” support • Data dictionary
• JBOD improvements • Tracing
• Off-heap bloom ﬁlters,
compression metadata
• Parallel leveled
compaction

©2012 DataStax

Concurrent Schema Changes
CREATE TABLE X;
...
DROP TABLE X;

Client

Cassandra
Cluster

Client

CREATE TABLE Y;
...
©2012 DataStax
DROP TABLE Y;

Virtual nodes

A C D
B E

A F
F B

P G
Ring without
Ring with vnodes
vnodes O H

E C N I

M J
D L K

©2012 DataStax

Node Rebuild without vnodes
Node 1 Node 2 Node 3
A B C

F E A F B A
A

F B

Ring without
vnodes
E C

D

D E F

C B D C E D


©2012 DataStax

Node Rebuild with vnodes
B E A P K G

G K M O C N
C D D J D H J F
B E
A F L A K F P I

P Ring with G

O VNodes H

N I M O E P H C
M J
L K I H I A B O

B L M C N E

F D G N J L


©2012 DataStax

JBOD support

Cassandra
Instance

HDD1 HDD2 HDD3 HDD4

©2012 DataStax

JBOD support

Cassandra
Instance

HDD1
X
HDD2 HDD3 HDD4

©2012 DataStax

Moving O(n) structures off-heap
• Row (partition) bloom ﬁlter
• 1-2GB per billion rows

• Compression metadata
• ~20GB per TB compressed data

©2012 DataStax

On-Heap/Off-Heap

On-Heap Off-Heap
Managed by GC Not managed by GC

JVM Java Heap Native Memory

Java Process

©2012 DataStax

Batches

Partition
Replica

Coordinator Partition
Client
Node Replica

Partition
Replica

©2012 DataStax

Batches

Partition
Replica

Client

X
Coordinator
Node
Partition
Replica

Partition
Replica

©2012 DataStax

Atomic batches

Partition
Replica

Coordinator Partition
Client
Node Replica

Partition
Batchlog Replica
Node

©2012 DataStax

Atomic batches

Partition
Replica

Client

X
Coordinator
Node
Partition
Replica

Partition
Batchlog Replica
Node

©2012 DataStax

CQL: You got SQL in my NoSQL!
CREATE TABLE users (
id uuid PRIMARY KEY,
name text,
state text,
birth_date int
);

CREATE INDEX ON users(state);

SELECT * FROM users WHERE state=‘Texas’ AND birth_date > 1950;

©2012 DataStax

Strictly “realtime” focused
• No joins
• No subqueries
• No aggregation functions* or GROUP BY
• Strictly limited ORDER BY

©2012 DataStax

songs
create column family songs
with key_validation_class = UUIDType
and comparator = UTF8Type -- cell names are strings
and column_metdata = [{column_name: title, validation_class: UTF8Type}
{column_name: album, validation_class: UTF8Type}
{column_name: artist, validation_class: UTF8Type
{column_name: data, validation_class: BytesType}

a3e64f8f... title: La Grange artist: ZZ Top album: Tres Hombres

8a172618... title: Moving in Stereo artist: Fu Manchu album: We Must Obey

2b09185b... title: Outside Woman Blues artist: Back Door Slam album: Roll Away

©2012 DataStax

CREATE TABLE songs (
id uuid PRIMARY KEY,
title text,
artist text,
album text,
data blob
);

id title artist album
a3e64f8f... La Grange ZZ Top Tres Hombres
8a172618... Moving in Stereo Fu Manchu We Must Obey
2b09185b... Outside Woman Blues Back Door Slam Roll Away

©2012 DataStax

song_tags
create column family song_tags
and comparator = UTF8Type;

a3e64f8f... blues: 1973:

8a172618... covers: 2003:

©2012 DataStax

CREATE TABLE song_tags (
id uuid,
tag_name text,
PRIMARY KEY (id, tag_name)
);

a3e64f8f... blues: 1973:

8a172618... covers: 2003:

id tag_name

a3e64f8f... blues
a3e64f8f... 1973
8a172618... covers
8a172618... 2003
©2012 DataStax

Easier way to add tags
ALTER TABLE songs ADD tags set<text>;

id title artist album tags
a3e64f8f... La Grange ZZ Top Tres Hombres {blues, 1973}
8a172618... Moving in Stereo Fu Manchu We Must Obey {covers, 2003}
2b09185b... Outside Woman Blues Back Door Slam Roll Away

©2012 DataStax

playlists
create column family playlists
and comparator = 'CompositeType(UTF8Type, UTF8Type, UTF8Type)'
and default_validation_class = UUIDType;

62c36092... La Grange, Moving in S..., Outside Wo...,
ZZ Top, : a3e64f8f... Fu Manchu, : 8a172618... Back Door ..., : 2b09185b...
Tres Hombres We Must O... Roll Away

©2012 DataStax

CREATE TABLE playlists (
id uuid,
title text,
album text,
artist text,
song_id uuid,
PRIMARY KEY (id, title, album, artist)
);

62c36092... La Grange, Moving in S..., Outside Wo...,
ZZ Top, : a3e64f8f... Fu Manchu, : 8a172618... Back Door ..., : 2b09185b...
Tres Hombres We Must O... Roll Away

id title artist album song_id
62c36092... La Grange ZZ Top Tres Hombres a3e64f8f...
62c36092... Moving in Stereo Fu Manchu We Must Obey 8a172618...
62c36092...
©2012 DataStax Outside Wo... Back Door Slam Roll Away 2b09185b...

Clustering
CREATE TABLE timeline ( user_id tweet_id _author _body
  user_id uuid, jbellis 3290f9da.. rbranson lorem
  tweet_id timeuuid,
jbellis 3895411a.. tjake ipsum
  tweet_author uuid,
... ... ...
tweet_body text,
  PRIMARY KEY (user_id, driftx 3290f9da.. rbranson lorem
tweet_id) driftx 71b46a84.. yzhang dolor
); ... ... ...
yukim 3290f9da.. rbranson lorem
SELECT * FROM timeline yukim e451dd42.. tjake amet
WHERE user_id = ’driftx’; ... ... ...

©2012 DataStax

Data dictionary
cqlsh:system> SELECT * FROM schema_keyspaces;

keyspace_name | durable_writes | strategy_class | strategy_options
---------------+----------------+----------------+----------------------------
keyspace1 | True | SimpleStrategy | {"replication_factor":"1"}
system | True | LocalStrategy | {}
system_traces | True | SimpleStrategy | {"replication_factor":"1"}

©2012 DataStax

Data dictionary

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

cqlsh:system> SELECT * FROM schema_columnfamilies WHERE keyspace_name='keyspace1' AND
columnfamily_name='test';

©2012 DataStax

Data dictionary

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

cqlsh:system> SELECT * FROM schema_columnfamilies WHERE keyspace_name='keyspace1' AND

cqlsh:system> SELECT * FROM schema_columns WHERE keyspace_name='keyspace1' AND

©2012 DataStax

Data dictionary
cqlsh:system> SELECT * FROM local;

key | bootstrapped | cluster_name | cql_version | data_center | gossip_generation |
partitioner | rack | release_version | ring_id
| thrift_version | tokens | truncated_at
-------+--------------+--------------+-------------+-------------+-------------------
+---------------------------------------------+-------+----------------------
+--------------------------------------+----------------+--------+--------------
local | COMPLETED | test | 3.0.0 | datacenter1 | 1352846064 |
org.apache.cassandra.dht.Murmur3Partitioner | rack1 | 1.2.0-beta2-SNAPSHOT |
224c55d5-21b4-42b0-8969-afc0cc04e812 | 19.35.0 | {0} | null

©2012 DataStax

Data dictionary
cqlsh:system> SELECT * FROM peers LIMIT 1;

peer | data_center | rack | release_version | ring_id
| rpc_address | schema_version | tokens
-----------+-------------+-------+----------------------
+--------------------------------------+-------------
+--------------------------------------+-----------------------
127.0.0.3 | datacenter1 | rack1 | 1.2.0-beta2-SNAPSHOT | f6782327-
ef8e-41cf-87b9-2edc287b1ffe | 127.0.0.3 | 915ed888-ddd0-3448-860c-582f4eea1bc6 |
{6148914691236517204}

©2012 DataStax

Request tracing
cqlsh:foo> INSERT INTO bar (i, j) VALUES (6, 2);
Tracing session: 4ad36250-1eb4-11e2-0000-fe8ebeead9f9

activity | timestamp | source | source_elapsed
-------------------------------------+--------------+-----------+----------------
Determining replicas for mutation | 00:02:37,015 | 127.0.0.1 | 540
Sending message to /127.0.0.2 | 00:02:37,015 | 127.0.0.1 | 779
Message received from /127.0.0.1 | 00:02:37,016 | 127.0.0.2 | 63
Applying mutation | 00:02:37,016 | 127.0.0.2 | 220
Acquiring switchLock | 00:02:37,016 | 127.0.0.2 | 250
Appending to commitlog | 00:02:37,016 | 127.0.0.2 | 277
Adding to memtable | 00:02:37,016 | 127.0.0.2 | 378
Enqueuing response to /127.0.0.1 | 00:02:37,016 | 127.0.0.2 | 710
Processing response from /127.0.0.2 | 00:02:37,017 | 127.0.0.1 | 2550

©2012 DataStax

Tracing an antipattern
CREATE TABLE queues (
id text,
created_at timeuuid,
value blob,
PRIMARY KEY (id, created_at)
);

id created_at value

myqueue 3092e86f 9b0450d30de9
myqueue 0867f47c fc7aee5f6a66
myqueue 5fc74be0 668fdb3a2196

©2012 DataStax

CREATE TABLE queues (
id text,
created_at timeuuid,
value blob,
PRIMARY KEY (id, created_at)
);

id created_at value

myqueue 3092e86f 9b0450d30de9
myqueue 0867f47c fc7aee5f6a66
myqueue 5fc74be0 668fdb3a2196

©2012 DataStax

cqlsh:foo> SELECT FROM queues WHERE id = 'myqueue' ORDER BY created_at LIMIT 1;
Tracing session: 4ad36250-1eb4-11e2-0000-fe8ebeead9f9

activity | timestamp | source | source_elapsed
------------------------------------------+--------------+-----------+---------------
execute_cql3_query | 19:31:05,650 | 127.0.0.1 | 0
Executing single-partition query | 19:31:05,652 | 127.0.0.3 | 943
Acquiring sstable references | 19:31:05,652 | 127.0.0.3 | 973
Merging memtable contents | 19:31:05,652 | 127.0.0.3 | 1020
Merging data from memtables and sstables | 19:31:05,652 | 127.0.0.3 | 1081
Read 1 live cells and 100000 tombstoned | 19:31:05,686 | 127.0.0.3 | 35072
Enqueuing response to /127.0.0.1 | 19:31:05,687 | 127.0.0.3 | 35220
Processing response from /127.0.0.3 | 19:31:05,688 | 127.0.0.1 | 37650
Request complete | 19:31:05,688 | 127.0.0.1 | 38047

©2012 DataStax

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