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pgagroal pipelines

pgagroal supports 3 different pipelines

• Performance
• Session
• Transaction

The pipeline is defined in pgagroal.conf configuration file under the setting of "pipeline".

pgagroal will choose either the performance or the session pipeline based on the configuration settings by default.

Performance

The performance pipeline is fastest pipeline as it is a minimal implementation of the pipeline architecture.

However, it doesn't support Transport Layer Security (TLS), failover support and the "disconnect_client" setting.

A "DISCARD ALL" query is run after each client session.

Select the performance pipeline by

pipeline = performance
    

Session

The session pipeline supports all features of pgagroal.

A "DISCARD ALL" query is run after each client session.

Select the session pipeline by

pipeline = session
    

Transaction

The transaction pipeline will release the connection back to the pool after each transaction completes. This feature will support many more clients than there are database connections.

However, there are some session based features of PostgreSQL that can't be supported in this pipeline.

• SET / RESET
• LISTEN / NOTIFY
• WITH HOLD CURSOR
• PREPARE / DEALLOCATE

It is assumed that all clients using the same user name and database pair share the same startup parameters towards PostgreSQL.

SET / RESET
The "SET" functionality is a session based feature.

LISTEN / NOTIFY
The "LISTEN" functionality is a session based feature.

WITH HOLD CURSOR
The "WITH HOLD CURSOR" functionality is a session based feature.

PREPARE / DEALLOCATE
While using "PREPARE" and "EXECUTE" can be used the prepared statements are tied to the connection they were created in which means that clients can't be sure that they created the prepared statement on the connection unless it is issued within the same transaction where it is used.

pgagroal can issue a "DEALLOCATE ALL" statement before a connection is returned back to the pool if the "track_prepared_statements" setting is set to "on". If "off" then no statement is issued.

Note, that pgagroal does not issue a "DISCARD ALL" statement when using the transaction pipeline.

Performance considerations
Clients may need to wait for a connection between transactions leading to a higher latency.

Important
Make sure that the "blocking_timeout" settings to set to 0. Otherwise active clients may timeout during their workload. Likewise it is best to disable idle connection timeout by setting "idle_timeout" to 0.

It is highly recommended that you prefill all connections for each user.

The transaction pipeline doesn't support the "disconnect_client" setting.

Select the transaction pipeline by

pipeline = transaction