This document discusses PostgreSQL replication. It covers the different use cases for replication including high availability, scalability, and protection. It describes the different replication mechanisms in PostgreSQL, including trigger-based and log-based replication. It outlines the developments made to log shipping in different PostgreSQL versions. It focuses on streaming replication introduced in version 9.0, describing the wal sender, wal receiver, and hot standby capabilities. It discusses tools like Repmgr that help manage replication and monitor delays. Future planned features like sync replication and loose coupling of replication are also mentioned.

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Managing
PostgreSQL
Replication

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Who Am I?
• Simon Riggs
• Major Developer on PostgreSQL project
• CTO, 2ndQuadrant

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Replication Use Cases
• High Availability
• Scalability
• Protection
• Total Cost of
Ownership
• Exploiting success

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Replication Mechanisms
• Trigger-based replication
– User space solution
• Log-based replication
– Integrated development

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Log Shipping Developments
• 8.0 – Point in Time Recovery, Full WAL info
• 8.2 – Restartable Recovery, Log Switching,
Streaming API
• 8.3 – Full Page Optimization, pg_standby
• 8.4 – BgWriter during Recovery
• 9.0 – Streaming Replication
Hot Standby

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Streaming Replication (9.0)
• Efficient real-time “log shipping”
• Master → Slave replication using full security
• Multiple concurrent slaves
• Robust bi-modal design

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WAL Sender

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WAL Receiver

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Hot Standby
• Read-only access while “in recovery”
• Equivalent of Oracle 11g Active Data Guard
• Load balanced read scalability
• Query off-load from main write node
• Multiple highly available standby nodes

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Capabilities
• High Performance
• Integrated
• Ease of Use
• Query Access
• Relay
• Selectivity
• Query Farm

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Capabilities with Tools
• High Performance
• Integrated
• Ease of Use
• Query Access
• Relay
• Selectivity
• Query Farm

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Repmgr

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Repmgr
• Simplify standby management
• Monitor replication delays
• Provide feedback mechanisms

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Future: Sync Replication (9.1)
• User-controlled robustness
• High performance design
• Simplicity
• Additional flexibility through registration

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Future: Loose Coupling
• Allows distributed database
• High Availability and Disaster Recovery
• No shared resources – better scalability
• “Cellular” approach

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PostgreSQL Books
• http://www.2ndQuadrant.com/books/