What is a replication slot?

What is a replication slot?

What are replication slots? Streaming replication slots are a new facility introduced in PostgreSQL 9.4. They are a persistent record of the state of a replica that is kept on the master server even when the replica is offline and disconnected.

How do I cancel my PostgreSQL subscription?

A subscription can only be dropped by a superuser. DROP SUBSCRIPTION cannot be executed inside a transaction block if the subscription is associated with a replication slot. (You can use ALTER SUBSCRIPTION to unset the slot.)

What is Pg_recvlogical?

pg_recvlogical controls logical decoding replication slots and streams data from such replication slots. It sends replay confirmations for data lazily as it receives it and on clean exit. To examine pending data on a slot without consuming it, use pg_logical_slot_peek_changes .

What is Max_wal_senders?

max_wal_senders (integer) Specifies the maximum number of concurrent connections from standby servers or streaming base backup clients (i.e., the maximum number of simultaneously running WAL sender processes). The default is zero, meaning replication is disabled.

What is streaming replication?

Streaming Replication (SR) provides the capability to continuously ship and apply the WAL XLOG records to some number of standby servers in order to keep them current. This feature was added to PostgreSQL 9.0. The discussion below is a developer oriented one that contains some out of date information.

How does streaming replication work in Postgres?

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 Pglogical replication?

pglogical is a logical replication system implemented entirely as a PostgreSQL extension. Fully integrated, it requires no triggers or external programs. This alternative to physical replication is a highly efficient method of replicating data using a publish/subscribe model for selective replication.

How are replication slots created in PostgreSQL 10?

So a physical replication slot can be created on the primary server and the location up to where the transactions have been sent to the standby is stored. Now when the standby loses connection, the primary server will keep those WAL files. Logical replication was introduced in PostgreSQL 10.

What happens if there is failover of logical replication slots?

So if there is a failover, new primary (the old physical standby) won’t be aware of any slots which were existing with old primary. This leads to a completely broken logical replication (not continuous) downstream.

What’s the difference between physical replication and logical replication?

Can be used for standard streaming replication. They will make sure that data is not recycled too early. Logical replication does the same thing as physical replication slots and are used for logical replication. However, they are used for logical decoding.

Why does an orphan replication slot cause unbounded disk growth?

An orphan replication slot can cause unbounded disk growth due to piled up WAL files from the master Slave nodes placed under long maintenance (such as days or weeks) and that are tied to a replication slot will have unbounded disk growth due to piled up WAL files from the master