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PostgreSQL Performance & Query Optimization · Lección

Estrategias de replicación (streaming, lógica)

Comprenda y configure diversos métodos de replicación, como la replicación por streaming y lógica, para lograr alta disponibilidad y escalar las lecturas.

Estrategias de replicación (streaming, lógica) es una lección gratuita de PostgreSQL Performance & Query Optimization en CoddyKit. Esta es la lección 2 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de PostgreSQL Performance & Query Optimization, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de PostgreSQL Performance & Query Optimization incluye 4 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

Why Data Replication?

Imagine your database goes down! Replication is key to preventing data loss and ensuring your application stays online. It creates copies of your database.

It's vital for:

  • High Availability (HA): If the main server fails, a copy can take over.
  • Read Scaling: Distribute read queries across multiple servers, reducing load on the primary.

The Primary-Replica Setup

The most common replication setup is a Primary-Replica (or Master-Slave) model. One database server acts as the primary, handling all writes.

  • Primary: Processes all write operations (INSERT, UPDATE, DELETE).
  • Replica(s): Receive copies of data changes from the primary and can serve read-only queries.

This ensures data consistency and offloads read traffic.

Streaming Replication: The Basics

Streaming Replication is PostgreSQL's built-in, physical replication method. It works by continuously shipping the Write-Ahead Log (WAL) records from the primary to one or more replicas.

WAL records are low-level descriptions of every change made to the database. Replicas apply these changes to stay in sync.

WAL Shipping in Action

Here's how streaming replication works:

  • The primary server writes all database changes to its WAL files.
  • A dedicated process (WAL sender) on the primary sends these WAL records to replica servers.
  • A process (WAL receiver) on each replica receives and applies these records.

This keeps the replica's data identical to the primary's, block by block.

Setting Up Streaming Replication (Primary)

To enable streaming replication on the primary, you need to configure postgresql.conf:

  • wal_level = replica (or higher)
  • max_wal_senders = 10 (number of replicas/connections)
  • listen_addresses = '*' (allow connections from replicas)

You'll also need to set up pg_hba.conf to allow replica connections.

ALTER SYSTEM SET wal_level = 'replica';
ALTER SYSTEM SET max_wal_senders = 10;
ALTER SYSTEM SET listen_addresses = '*';

-- After these, restart PostgreSQL

Initializing a Replica with pg_basebackup

Before a replica can stream WAL, it needs a full copy of the primary's data. pg_basebackup is the standard tool for this.

It creates a consistent snapshot of the primary's data directory, which then becomes the replica's initial data.

pg_basebackup -h primary_host -p 5432 -U replication_user -D /var/lib/postgresql/data_replica -F p -Xs stream -P

Configuring the Replica

After pg_basebackup, the replica needs a few files:

  • A standby.signal file in its data directory (for PostgreSQL 12+).
  • A postgresql.conf with hot_standby = on (if you want to run queries).
  • A primary_conninfo setting in postgresql.conf to tell it where to connect to the primary.

This allows it to start up and connect as a replica.

ALTER SYSTEM SET hot_standby = 'on';
ALTER SYSTEM SET primary_conninfo = 'host=primary_host port=5432 user=replication_user password=your_password';

-- Create an empty standby.signal file:
touch /var/lib/postgresql/data_replica/standby.signal

-- Then start the replica PostgreSQL instance

Logical Replication: A Different Approach

Logical Replication is a newer, more flexible replication method introduced in PostgreSQL 10. Unlike streaming replication, it replicates data based on its logical representation (row changes, not physical blocks).

This allows for selective replication of tables or even databases, and cross-version/cross-platform replication.

Publications and Subscriptions

Logical replication uses a publish-subscribe model:

  • A Publication is created on the primary, defining which tables or changes to publish.
  • A Subscription is created on the replica, defining which publications to subscribe to.

The primary then sends logical decoding output (changes) to the subscribers, which apply them.

Setting Up Logical Replication (Example)

Here's a simplified example of setting up logical replication:

On Primary:

CREATE PUBLICATION my_pub FOR TABLE my_table;

On Replica:

CREATE SUBSCRIPTION my_sub CONNECTION 'host=primary_host dbname=mydb user=repl_user password=xyz' PUBLICATION my_pub;

Remember to configure wal_level = logical and max_replication_slots on the primary.

ALTER SYSTEM SET wal_level = 'logical';
ALTER SYSTEM SET max_replication_slots = 5;

-- On Primary:
CREATE PUBLICATION my_pub FOR TABLE my_table;

-- On Replica:
CREATE SUBSCRIPTION my_sub CONNECTION 'host=primary_host dbname=mydb user=repl_user password=xyz' PUBLICATION my_pub;

Replication Strategy Check

You need to set up replication for a PostgreSQL database. You want an exact, block-for-block copy of your entire database on a standby server for high availability. Which replication method is best suited for this goal?

Recap: Streaming vs. Logical

We've explored two key PostgreSQL replication strategies:

  • Streaming Replication: A physical, continuous copy of the entire database using WAL files. Great for high availability and read scaling with identical replicas.
  • Logical Replication: A flexible, publish-subscribe model replicating logical changes (rows). Ideal for selective replication, cross-version upgrades, or integrating with other systems.

Choosing the right strategy depends on your specific needs for consistency, flexibility, and performance.

Preguntas frecuentes

¿La lección «Estrategias de replicación (streaming, lógica)» es gratis?

Sí — el texto completo de «Estrategias de replicación (streaming, lógica)» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de PostgreSQL Performance & Query Optimization, actualiza a CoddyKit PRO. El curso de PostgreSQL Performance & Query Optimization incluye 4 lecciones en total.

¿Qué aprenderé en «Estrategias de replicación (streaming, lógica)»?

Comprenda y configure diversos métodos de replicación, como la replicación por streaming y lógica, para lograr alta disponibilidad y escalar las lecturas. Practicas PostgreSQL Performance & Query Optimization con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar PostgreSQL Performance & Query Optimization?

No se requiere experiencia previa. PostgreSQL Performance & Query Optimization en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 2 de 4.

¿Cuánto tiempo toma la lección «Estrategias de replicación (streaming, lógica)»?

La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.

¿Puedo escribir y ejecutar código en esta lección de PostgreSQL Performance & Query Optimization?

Sí. Cada lección de PostgreSQL Performance & Query Optimization incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.

Todas las lecciones de este curso

  1. Agrupación de conexiones con PgBouncer
  2. Estrategias de replicación (streaming, lógica)
  3. Sharding y PostgreSQL distribuido
  4. Escalado de lecturas con Hot Standby y balanceo de carga
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