High Availability and Clustering in PostgreSQL

1. Introduction

High availability (HA) and clustering are crucial for modern database systems to ensure uninterrupted access to data and resilience against failures. This lesson will explore PostgreSQL's capabilities in providing HA and clustering solutions.

2. Key Concepts

Understanding high availability and clustering in PostgreSQL requires familiarity with the following concepts:

• **Replication**: The process of copying data from one database to another.
• **Failover**: The process of switching to a redundant or standby database upon the failure of the primary database.
• **Load Balancing**: Distributing workloads across multiple databases to optimize resource use and avoid overload.
• **Clustering**: Grouping multiple databases to work together as a single system.

3. High Availability

High availability in PostgreSQL is achieved through replication and failover mechanisms:

4. Clustering

PostgreSQL can be clustered using different methods:

5. Step-by-Step Setup

Here’s how to set up streaming replication:

1. **Configure the Primary Server**:

 
# In postgresql.conf
wal_level = replica
max_wal_senders = 3
hot_standby = on
                

2. **Set Up the Replication User**:

CREATE ROLE replicator WITH REPLICATION LOGIN PASSWORD 'password';
                

3. **Configure pg_hba.conf**:

host    replication     replicator      standby_ip/32      md5
                

4. **Start the Standby Server**:

# In recovery.conf
standby_mode = 'on'
primary_conninfo = 'host=primary_ip port=5432 user=replicator password=password'
                

6. Best Practices

To ensure a reliable high availability setup, consider the following:

• Regularly test failover and recovery procedures.
• Monitor replication lag to ensure timely data consistency.
• Keep your PostgreSQL version up to date to benefit from the latest features and security fixes.

7. FAQ