Apache Cassandra and Drivers

Apache Cassandra and DriversOverview of Apache Cassandra and DataStax Drivers

Bulat Shakirzyanov@avalanche123

Sandeep Tamhankar@stamhankar999

https://goo.gl/cBsRVv

IntroductionCassandra Overview

© 2015 DataStax, All Rights Reserved.

Datacenter Datacenter

Cassandra Topology

3

Node

NodeNode

Node

Client Client

Node

NodeNode

Node

Client Client

Cluster



Request Coordinator

4

Node

NodeNode

Node

Client Client

Node

NodeCoordinator

Node

Client Client

Coordinator node:Forwards requeststo corresponding replicas


Datacenter

Row Replica

5

Replica

NodeNode

Replica

Client Client

Datacenter

Node

Node

Replica

Client Client

Coordinator

Replica node:Stores a slice of total rows of each keyspace


Token Ring

6

121

2

3

4567

8

9

1011


Token Ring

6

-263 … (+263 - 1)

Murmur3 Partitioner


Token Ring

6

Node

11…12Node

12…1

Node

1…2

Node

2…3

Node

3…4

Node

4…5

Node

5…6Node

6…7

Node

7…8

Node

8…9

Node

9…10

Node

10…11

-263 … (+263 - 1)

Murmur3 Partitioner


Keyspaces

7

CREATE KEYSPACE default WITH replication = { 'class': 'SimpleStrategy', 'replication_factor': 3 }


C*

Data Partitioning

8

KeyspaceRow

token(PK) = 1RF = 3

Partitioner:Gets a token by hashing the primary key of a row


C*

Replication Strategy

9

Keyspace 1

Row

RF = 3

Replication strategy:Determines the first

replica for the row

token(PK) = 1


C*

Replication Factor

10

KeyspaceRow

RF = 3

Replication factor:Specifies total number of replicas for each row

token(PK) = 1


Coordinator

Node Replica

ReplicaNode

11

ReplicaApplication

Consistency Level

RF = 3, CL = Quorum


Coordinator

Node Replica

ReplicaNode

11

ReplicaApplication

Consistency Level

RF = 3, CL = Quorum

INSERT

DataStax DriversSmart clients for Apache Cassandra


Goals of DataStax Drivers

• Consistent set of features across languages• Asynchronous execution of requests• Load balancing• Fault tolerant• Address Resolution (multi-region!)• Automatic cluster discovery and reconnection

• Flexible to the core• Consistent terminology• Open source

13

Asynchronous ExecutionIO Reactor, Request Pipelining and Future Composition


Asynchronous Core

16

Application Thread

Business Logic

Driver

Background Thread

IO Reactor


Request Pipelining

17

Client

WithoutRequest Pipelining

Server

Client Server WithRequest Pipelining

1

2

2

3

1

3

1

2

3

1

2

3


What is a Future?

• Represents the result of an asynchronous operation• Returned by any *_async method in the Ruby driver

• execute_async• prepare_async

• Will block if asked for the true result

18


Future Composition

19

select_user = session.prepare('SELECT * FROM users WHERE id = ?') select_page = session.prepare('SELECT * FROM pages WHERE slug = ?') user_ids = [1, 2, 3, 4] futures = user_ids.map do |id| future = session.execute_async(select_user, arguments: [id])

future.then do |users| user = users.first future = session.execute_async(select_page, arguments: [user['username']])

future.then do |pages| page = pages.first

User.new(user, Page.new(page)) end end end Cassandra::Future.all(futures).get






Future Composition

20






Future Composition

21






Future Composition

22






Future Composition

23






Future Composition

24


Future Composition

25

[#<User @id=1 @username="avalanche123"; @page=#<Page @slug="avalanche123" ... > ... >, ... ]


Pop Quiz: How to make this faster?

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Pop Quiz: How to make this faster?

27

user_future = session.prepare_async(‘SELECT * FROM users WHERE id = ?') page_future = session.prepare_async(‘SELECT * FROM pages WHERE slug = ?’) user_ids = [1, 2, 3, 4] futures = user_ids.map do |id| future = session.execute_async(user_future.get, arguments: [id])

future.then do |users| user = users.first future = session.execute_async(page_future.get, arguments: [user['username']])



Load BalancingPrinciples and Implementations


Application Driver

Load Balancing

29

ApplicationThread

Node

Pool

SessionPool

Pool

Pool

ApplicationThread

ApplicationThread

Client Cluster

Node

Node

Node

Load Balancing Policy


Datacenter

Datacenter

DataCenter Aware Balancing

30

Node

Node

NodeClient

Node

Node

Node

Client

Client

Client

Client

Client

Local nodes are queried first, if none are available, the request could be sent to a remote node.


Token Aware Balancing

31

Route request directly to Replicas

Node

Node

ReplicaNode

Client

Replica

Replica

Uses prepared statement metadata to get the token


Other built-in policies

• Round Robin Policy• ignores topology

• White List Policy• only connect with certain hosts

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Fault ToleranceSources of Failure and Error Handling


Fault Tolerance

34

Coordinator

Node Replica

Replica

ReplicaNode

Business Logic

Driver

Application


Coordinator

Node Replica

Replica

ReplicaNode

Business Logic

Driver

Application

Invalid Requests

Network Timeouts

Server ErrorsPossible Failures


Application Driver

Automatic Retry of Server Errors

36

ApplicationThread

Node

Pool

SessionPool

Pool

Pool

ApplicationThread

ApplicationThread

Client Cluster

Node

Node

Node

Load Balancing Policy


Coordinator

Node Replica

Replica

ReplicaNode

Business Logic

Driver

Application

Unreachable Consistency


Coordinator

Node Replica

ReplicaNode

38

Replica

Business Logic

Driver

Application

Read / Write Timeout Error


Coordinator

Node Replica

ReplicaNode

38

Replica

Business Logic

Driver

Application

Read / Write Timeout Error

read / write timeout


Coordinator

Node Replica

Replica

ReplicaNode

Business Logic

Driver

Application

Unavailable Error


Coordinator

Node Replica

Replica

ReplicaNode

Business Logic

Driver

Application

Unavailable Error

unavailable


Error Handling

Address ResolutionTopology Aware Client



Multiple Addresses

42

Node

NodeNode

Node

Client Client

Node

NodeNode

Node

Client Client

Within Datacenter: Private IPs

Across Datacenters: Public IPs


Application Driver

Address Resolution

43

ApplicationThread

ApplicationThread

ApplicationThread

Client Cluster


Application Driver

Address Resolution

43

ApplicationThread Node

Cluster

ApplicationThread

ApplicationThread

Client Cluster

Address Resolution Policy


Application Driver

Address Resolution

43


Cluster

ApplicationThread

ApplicationThread

Client Cluster

Node

Node

Node


Control Connection


Application Driver

Address Resolution

43


Pool

Cluster

Pool

Pool

Pool

ApplicationThread

ApplicationThread

Client Cluster

Node

Node

Node


Control Connection

Session


EC2 Multi-Region Address Resolution

44


More

• Request Tracing• Execution Information

• which node was used, # retries for query, etc.• State Listeners

• node goes down/comes up, schema changes, etc.• Result Paging• SSL and Authentication

45

Questions

Apache Cassandra and Drivers

Technology

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