What is PostgreSQL streaming replication?

Streaming replication, a standard feature of PostgreSQL, allows the updated information on the primary server to be transferred to the standby server in real time, so that the databases of the primary server and standby server can be kept in sync.

What is stream replication?

Overview of Streams Replication. Replication is the process of sharing database objects and data at multiple databases. To maintain replicated database objects and data at multiple databases, a change to one of these database objects at a database is shared with the other databases.

Does PostgreSQL have replication?

The process of copying data from a PostgreSQL database server to another server is called PostgreSQL Replication. The source database server is usually called the Master server, whereas the database server receiving the copied data is called the Replica server.

How does Postgres replication work?

Streaming replication in PostgreSQL works on log shipping. Every transaction in postgres is written to a transaction log called WAL (write-ahead log) to achieve durability. A slave uses these WAL segments to continuously replicate changes from its master.

What is WAL in PostgreSQL?

WAL (write-ahead log) is the log of changes made to the database cluster which is replayed either as part of the database recovery process when a database isn’t shutdown correctly (such as when a crash occurs), or is used by standbys to replay the changes to replicate the database.

Does PostgreSQL support sharding?

PostgreSQL does not natively support sharding and distributing data across multiple physical clusters (yet). Foreign data wrappers serve as a tool to read data from remote servers and can be used to distribute data.

What is physical replication in PostgreSQL?

Physical replication methods are used to maintain a full copy of the entire data of a single cluster (in Postgres, a cluster is a set of databases managed by a single main Postgres server process called a postmaster), typically on another machine.

Is Postgres replication synchronous?

Synchronous Replication. PostgreSQL streaming replication is asynchronous by default. If the primary server crashes then some transactions that were committed may not have been replicated to the standby server, causing data loss. The amount of data loss is proportional to the replication delay at the time of failover.

What is WAL or XLOG Postgres?

In PostgreSQL, the history data are known as XLOG record(s) or WAL data. XLOG records are written into the in-memory WAL buffer by change operations such as insertion, deletion, or commit action. They are immediately written into a WAL segment file on the storage when a transaction commits/aborts.

What is checkpoint in Postgres?

Description. A checkpoint is a point in the write-ahead log sequence at which all data files have been updated to reflect the information in the log. All data files will be flushed to disk.

How to configure streaming replication on PostgreSQL instances?

Overview. PostgreSQL supports different type of replications,i.e.

  • Install Postgresql-13 from source code. In this blog,we will install Postgresql from the source code,so that this environment can be used for later development.
  • Setup Primary Server
  • Setup Standby Server.
  • Create replication slot on Primary Server.
  • Start Standby Server.

    • How do I know Postgres streaming replication is working?

    wal_level: This is used to enable PostgreSQL streaming replication.

  • wal_log_hints: It is required for the pg_rewind capability,this helps when the standby server is out of sync with the master server.
  • max_wal_senders: It is used to specify the maximum number of concurrent connections that can be established with the standby servers.

    • How to change PostgreSQL IP address for streaming replication?

    The -h option specifies a non-local host.

  • The -p option specifies the port number it connects to on the primary server.
  • The -U option allows you to specify the user you connect to the primary cluster as.
  • The -D flag is the output directory of the backup.
  • The -Fp specifies the data to be outputted in the plain format instead of as a tar file.

    • How reliable is PostgreSQL replication?

    Setup Primary (Read/Write) Server. Now,if this is a new installation,we need to create the data directory.

  • Setup Standby/Replica Servers. It is likely you don’t want any activity on the primary server (db01) while we set up the replicas.
  • Try it out.
  • DNS and Failover.
  • High Availability.