Postgresql – horizontal scaling and load-balancing for PostgreSQL with ProxySQL

No it's a very precise statistic. A "logical processor" is a core. And a core is just that, it doesn't matter how they're spread over physical processors.

And if you're dealing with a machine with more cores than the supported number, this shouldn't be an issue with PostgreSQL. Each connection is inherently single-threaded* so whatever number of cores you have is what's going to limit the efficiency and efficacy of concurrent connections.

Needless to say this also means you should put your money in faster cores than quantity of cores unless you want to cluster things in a more complicated method.

_{* 2017 Update: Some queries (or subqueries) may be executed in parallel.}

First you have see the differences between both options load balancing (without cluster) and Cluster with replication.

Clustering has a formal meaning. A cluster is a group of resources that are trying to achieve a common objective, and are aware of one another. Clustering usually involves setting up the resources (servers usually) to exchange details on a particular channel (port) and keep exchanging their states, so a resource’s state is replicated at other places as well. It usually also includes load balancing, wherein, the request is routed to one of the resources in the cluster as per the load balancing policy.

A clustered architecture is used to solve one or more of the following problems:

• A single server cannot handle the high number of incoming requests efficiently
• A stateful application needs a way of preserving session data if its server fails
• A developer requires the capability to make configuration changes or deploy updates to their applications without discontinuing service.

A clustered architecture solves these problems using a combination of load balancing, multiple server to process the balanced load, and session replication.
In your case is not necessary session replication, for this I think a cluster configuration is not the approach that you need.

Documentation: Apache Tomcat - Clustering/Session Replication HOW-TO

Load balancing can also happen without clustering when we have multiple independent servers that have same setup, but other than that, are unaware of each other. Then, we can use a load balancer to forward requests to either one server or other, but one server does not use the other server’s resources. Also, one resource does not share its state with other resources.

The fundamental feature of a load balancer is to be able to distribute incoming requests over a number of backend servers in the cluster according to a scheduling algorithm.

On both architectures you need something that implements the load balancer, for this the one option is use Apache HTTP Server.

For implement a load balancer in Apache Http Server, you have some options as:

• Using the JK native connector
• Using Apache HTTP mod_proxy

Reference:

• not active link: The Apache Tomcat Connector - Generic HowTo
• not active link: Configure Tomcat with Apache using Proxy
• not active link: How to Configure Tomcat/JBoss and Apache HTTPD for Load Balancing and Failover
• Tomcat Clustering - A Step By Step Guide