How does load balancing in pgpool 2 work?
Pgpool-II load balancing of SELECT queries works with any clustering mode except raw mode. When enabled Pgpool-II sends the writing queries to the primary node in Native Replication mode, all of the backend nodes in Replication mode, and other queries get load balanced among all backend nodes.
When to use pgpool-II or PostgreSQL connection pooling?
Limiting Exceeding Connection -> When connections to PostgreSQL server reaches maximum limit, further connection will be rejected, whereas by using PgPool-II, exceeding connections are queued instead of being rejected right away. Replication -> This is not used as we are using AWS RDS Replication, which uses PostgreSQL native streaming replication.
What are the two modes of pgpool-II cluster?
PgPool-II operates in 2 modes: Single-Node and Cluster Mode. To simplify installation and configuration, I created a Docker image rds_pgpool . In this post, I will be focusing on setting up a 2-Node PgPool-II cluster using AWS EC2.
What does ” write query ” mean in pgpool 2?
Here “write query” means non SELECT DML or DDL. Before Pgpool-II 4.1 , SELECTs having write functions as specified in write or read_only function list is not regarded as a write query.) If write and read_only function list is empty, SELECT having functions which are not volatile is regarded as a read only query.
How to load balance with PostgreSQL connection pool?
Load Balancing: We want to offload some of the read requests to our read replicas. Connection Pool: Instead of receiving an error when connections to our master node reaches maximum, we want to queue it. Also, we want to reduce overhead by reusing database connections. In our case, we use AWS RDS for PostgreSQL in master-slave mode.
What do you need to know about pgpool?
For this article, while PgPool offers other features like load balancing and quorum management, we will look at it purely as a pooling mechanism. PgPool is a session-based connection pooler, which maintains already-established connections to the database by reusing them.
Why do I need a pgpool line in PostgreSQL?
The ‘pgpool’ line is required because pgpool must be able to connect to the database to check the status (such as if this is a master or slave database). It needs very little access so can be restricted to just the postgres database. More on this later.
What are the requirements for load balancing in PostgreSQL?
For a query to be load balanced, all the following requirements must be met: PostgreSQL version 7.4 or later either in replication mode or native replication mode the query must not be in an explicitly declared transaction (i.e. not in a BEGIN ~ END block)
Are there functions that are not load balanced?
SELECTs including functions not specified in this list are not load balanced. These are replicated among all the DB nodes in Replication mode, sent to the primary node only in other mode. You can use regular expression to match function names, to which ^ and $ are automatically added.