Enabling High-Availability with multi-site, rack aware replication

Alex MaPrincipal Solutions Engineer

read/write/update

Active

SERVER 1

Active

SERVER 2

Active

SERVER 3

APP SERVER 1

COUCHBASE Client Library

CLUSTER MAP

COUCHBASE Client Library

CLUSTER MAP

APP SERVER 2

Shard 5

Shard 2

Shard 9

Shard

Shard

Shard

Shard 4

Shard 7

Shard 8

Shard

Shard

Shard

Shard 1

Shard 3

Shard 6

Shard

Shard

Shard

Replica Replica Replica

Shard 4

Shard 1

Shard 8

Shard

Shard

Shard

Shard 6

Shard 3

Shard 2

Shard

Shard

Shard

Shard 7

Shard 9

Shard 5

Shard

Shard

Shard

Couchbase Basics

• Docs distributed evenly across servers

• Each server stores both active and replica docs Only one server active at a time

• Client library provides app with simple interface to database

• Cluster map provides map to which server doc is on App never needs to know

• App reads, writes, updates docs

• Multiple app servers can access same document at same time

Auto-Failover

SERVER 4 SERVER 5

Replica

Active

Replica

Active

App Server 1

COUCHBASE Client Library

CLUSTER MAP

COUCHBASE Client Library

CLUSTER MAP

App Server 2

Active

SERVER 1

Shard 5

Shard 2

Shard 9Shard

Shard

Shard

Replica

Shard 4

Shard 1

Shard 8Shard

Shard

Shard

Active

SERVER 2

Shard 4

Shard 7 Shard 8

Shard

Shard Shard

Replica

Shard 6

Shard 3 Shard 2

Shard

Shard Shard

Active

SERVER 3

Shard 1

Shard 3

Shard 6Shard

Shard

Shard

Replica

Shard 7

Shard 9

Shard 5Shard

Shard

Shard

• App servers accessing Shards

• Requests to Server 3 fail

• Cluster detects server failedo Promotes replicas of

Shards to activeo Updates cluster map

• Requests for docs now go to appropriate server

• Typically rebalance would follow

Shard 1 Shard 3

Shard

Rack-Zone Awareness

©2014 Couchbase, Inc.

• Grouping of servers into server groups so that each group is on a physically separate rack

• Ensures that replica data partitions are not on the same rack as the primary partitions

Servers 1, 2, 3 on Rack 1

Servers 4, 5, 6 on Rack 2

Servers 7, 8, 9 on Rack 3

Cluster has 2 replicas (3 copies of data)

This is a balanced configuration

Rack-Zone Awareness

©2014 Couchbase, Inc.

• If a entire server rack fails, data is still available

• If a entire cloud zone or a region fails, data is still available

©2014 Couchbase, Inc. — Proprietary and Confidential 6

Ping times EC2 Regions

7

Cross Datacenter Replication (XDCR)

• Replicates continuously data FROM source cluster to remote clusters may be spread across geo’s

• Supports unidirectional and bidirectional operation

• Application can read and write from both clusters (active – active replication)

• Automatically handles node addition and removal

• Replication throughput scales out linearly

• Simplified Administration via console, REST, and CLI

©2014 Couchbase, Inc.

8

Cross Datacenter Replication (XDCR) – Single Node Type

33 2Managed Cache

Dis

k Q

ueue

Disk

Replication Queue

App Server

Memory-to-Memory Replication to other node

Doc

Doc Doc

XDCR Queue

(New in 3.0) Memory-to-Memory Replication to remote cluster

Doc

©2014 Couchbase, Inc.

9

Cross Datacenter Replication (XDCR)

©2014 Couchbase, Inc.

Unidirectional Replication

• Hot spare / Disaster Recovery

• Development/Testing copies

• Integrate to Connector e.g. Solr, ElasticSearch

• Integrate to custom consumer

10

Cross Datacenter Replication (XDCR)

©2014 Couchbase, Inc.

Bidirectional Replication

• Multiple Active Masters

• Disaster Recovery

• Datacenter Locality

©2014 Couchbase, Inc. — Proprietary and Confidential 11

Putting it all together

Ec2 West - Cluster Ec2 East- Cluster

Group 1West 1-a

Group 2West 1-b

Group 3West 1-c

Group 1East 1-a

Group 2East 1-b

Group 3East 1-c

XDCR

Q&A