2015 03-31 dom-code_cassandra

Storing Data the Cassandra WayFreek van Polen

“Simplicity is the ultimate sophistication.”

-Leonardo Da Vinci

About Me

● Cognitive Artificial Intelligence @ UU● Almende:

– Researcher, self-organization, wireless sensor networks

● Sense:– First employee, developer, backend, team leader

Goal of this Talk

● Not to tell you to use Cassandra for everything

Goal of this Talk

● Not to tell you to use Cassandra for everything● Not to go into all gory details of Cassandra

Goal of this Talk

● Not to tell you to use Cassandra for everything● Not to go into all gory details of Cassandra● Not to show off my drawing skills

Goal of this Talk

● Introduce some database theory

Goal of this Talk

● Introduce some database theory● Make you enthusiastic about Cassandra

Goal of this Talk

● Introduce some database theory● Make you enthusiastic about Cassandra

Use the right tool for the job!

SQL vs NoSQL

Non relational data

● documents● graphs● key-value● wide-row

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“Ross”,“Lucas”

],“location”: “Infi”,“talks”: [

{“speaker”: “Arian”,“topic”: “functional js”

},{

“speaker”: “Freek”,“topic”: “cassandra”,“length”: 45

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Non relational data


Non relational data


“6573672017456”: “tom”

“9810919283853”: “mary”

“1129823948673”: “jane”

“9827712003003”: “dani”

Non relational data


Stock 1: [+3.23, +5.02, 2.45, 34.12, 12.65, +0.43]Stock 2: [+5.34, +6.34, +9.12, +0.53]Stock 3: [3.21, 5.32, 8.12, 0.53, 0.12, +0.43, +0.76, +2.55]

Scalability

Database [A-Z]

Scalability: replication

Database [A-Z]

Copy of Database [A-Z]

Scalability: sharding

Database [A-M]

Database [N-Z]

Scalability: combined(oh the horror)

Database [A-M] Copy of Database [A-M]

Database [N-Z] Copy of Database [N-Z]

Coordinator

Scalability: combined(oh the horror)

Database [A-M] Copy of Database [A-M]

Database [N-Z] Copy of Database [N-Z]

CAP theorem

CAP theorem

RDBMS

ACID & BASE

● Atomicity● Consistency● Isolation● Durability

● Basically● Available● Soft-state ● Eventual consistency

Cassandra \o/

Cassandra Cluster

● All nodes are equal● All nodes can process any request● Throughput and storage space scales linearly● Graceful degradation

Cassandra: Gossip

5

37

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8 2

46

Cassandra: Replication

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Token Ring


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[A - D]

[E - H]

[I - K]

[L - N][O - Q]

[R - T]

[U - W]

[X - Z]


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[A - D]

[E - H]

[I - K]

[L - N][O - Q]

[R - T]

[U - W]

[X - Z] replication = 3

Cassandra: Request Processing

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K: 12-24?


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K: 12-24? K: 12-24?


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K: 12-24!

K: 12-24!


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K: 12-24!


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K:22 = “tom”


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K:22 = “tom” K:22 = “tom”


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Got it!

Great success!


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K:22 = “tom”

K:22 = “tom”

K:22 = “jerry”


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K:22 = “tom”

K:22 = “tom”

K:22 = “jerry”

K:22 = “tom”


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K:22 = “tom”

K:22 = “tom”

K:22 = “tom”

Cassandra: Tunable Consistency

● Consistency.ANY

● Consistency.ONE

● Consistency.QOURUM

● Consistency.ALL

Cassandra: Data Model

CREATE TABLE transactions (account_id string,date timestamp,amount float,other_account string,PRIMARY KEY (account_id, date)

);

Cassandra: Data Model

CREATE TABLE transactions (account_id string,date timestamp,amount float,other_account string,PRIMARY KEY (account_id, date)

);

29-03-2015 15:23:45

29-03-2015 16:56:21

30-03-2015 04:00:00

NLRABOxxx amount: -143.90other: NLINGxxx

amount: -29.30other: NLABNxxx

amount: +2000.00other: NLASNxxx

Cassandra Data Model

● Primary Key #1:– Row key

– Unit of partitioning

● Primary Key #2:– Column key

– Order within row

– Order is preserved on disk!

Distributed Concurrent Writes

from: https://aphyr.com/posts/294-call-me-maybe-cassandra


● Last write wins● Paxos● Treat data as

immutable



● Cassandra trades consistency for availability, partition tolerance, and super easy administration...

● This is not for all use cases


THE use case: time series data

CREATE TABLE sensor_data ( sensor_id text, time timestamp, value text, PRIMARY KEY (sensor_id, time));

Thanks!

Cassandra?

2015 03-31 dom-code_cassandra

Software

Transcript of 2015 03-31 dom-code_cassandra