couchbase 20-xdcr-deep-dive-12012012
TRANSCRIPT
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Couchbase Server 2.0 and Cross Data Center replication
Dipti Borkar
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XDCR: Cross Data Center Replication
US DATA CENTER
EUROPE DATA CENTER
ASIA DATA CENTER
http://blog.groosy.com/wp-content/uploads/2011/10/internet-map.jpg
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Cross Data Center Replication – The basics
• Replicate your Couchbase data across clusters• Clusters may be spread across geos• Configured on a per-bucket basis• Supports unidirectional and bidirectional operation• Application can read and write from both clusters
(active – active replication)• Replication throughput scales out linearly• Different from intra-cluster replication
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Intra-cluster Replication
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Cross Datacenter Replication (XDCR)
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33 2
Single node - Couchbase Write Operation with XDCR2
Managed Cache
Dis
k Q
ueue
Disk
Replication Queue
App Server
Couchbase Server Node
Doc 1Doc 1
Doc 1
To other node
XDCR Queue
Doc 1
To other cluster
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Internal Data Flow
1. Document written to managed cache
2. Document added to intra-cluster replication queue
3. Document added to disk queue
4. XDCR push replicates to other clusters
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XDCR in action
COUCHBASE SERVER CLUSTERNYC DATA CENTERACTIVE
Doc
Doc 2
SERVER 1
Doc 9
SERVER 2 SERVER 3
RAM
Doc Doc Doc
ACTIVE
Doc
Doc
Doc RAM
ACTIVE
Doc
Doc
DocRAM
DISK
Doc Doc Doc
DISK
Doc Doc Doc
DISK
COUCHBASE SERVER CLUSTERSF DATA CENTER
ACTIVE
Doc
Doc 2
SERVER 1
Doc 9
SERVER 2 SERVER 3
RAM
Doc Doc Doc
ACTIVE
Doc
Doc
Doc RAM
ACTIVE
Doc
Doc
DocRAM
DISK
Doc Doc Doc
DISK
Doc Doc Doc
DISK
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XDCR ARCHITECTURE
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Bucket A
Bucket B
Bucket C
Cluster 1
Bucket A
Bucket B
Bucket C
Cluster 2
Bucket-level XDCR
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Continuous Reliable Replication
• All data mutations replicated to destination cluster• Multiple streams round-robin across vBuckets in
parallel (32 default)• Automatic resume after network disruption
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Cluster Topology Aware
• Automatically handles node addition and removal in source and destination clusters
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Efficient
• Couchbase Server de-duplicates writes to disk– With multiple updates to
the same document only the last version is written to disk
– Only this last change written to disk is passed to XDCR
• Document revisions are compared between clusters prior to transfer
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Active-Active Conflict Resolution
• Couchbase Server provides strong consistency at the document level within a cluster
• XDCR provides eventual consistency across clusters• If a document is mutated on both clusters, both
clusters will pick the same “winner”• In case of conflict, document with the most updates
will be considered the “winner”
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CONFIGURATION AND
MONITORING
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STEP 1: Define Remote Cluster
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STEP 2: Start Replication
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Monitor Ongoing Replications
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Detailed Replication Progress
• Source Cluster
• Destination Cluster
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XDCR TOPOLOGIES
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Unidirectional
• Hot spare• Read slave• Development/Testing copies
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Bidirectional
• Multiple Active Masters• Disaster Recovery• Datacenter Locality
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Chain
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Propagation
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XDCR in the Cloud
• Server Naming– Optimal configuration using DNS name that resolves to
internal address for intra-cluster communication and public address for inter-cluster communication
• Security– XDCR traffic is not encrypted, plan topology accordingly– Consider 3rd party Amazon VPN solutions
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USE CASES
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Data Locality
• Data closer to your users is faster for your users
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Disaster Recovery
• Ensure 24x7x365 data availability even if an entire data center goes down
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Development and Testing
• Test code changes with actual production data without interrupting your production cluster
• Give developers local databases with real data, easy to dispose and recreate
Test and Dev Staging Production
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Impact of XDCR on the cluster
Your clusters need to be sized for XDCR• XDCR is CPU intensive – Configure the number of parallel streams based on your CPU
capacity
• You are doubling your I/O usage– I/O capacity needs to be sized correctly
• You will need more memory particularly for bidirectional XDCR – Memory capacity needs to be sized correctly
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Additional Resources
• Couchbase Server Manual - http://www.couchbase.com/docs/couchbase-manual-2.0/couchbase-admin-tasks-xdcr.html
• Getting Started with XDCR blog - http://blog.couchbase.com/cross-data-center-replication-step-step-guide-amazon-aws
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Q & A
