Document the minimum and recommended resources for testing with make tests in the contributing guide

[bkhomuts]

Problem

Minimum requirements for make tests are not specified, as a result, Postgres may fail to launch, making it impossible to test changes.

Description

I created a VM with 8 GB RAM. When I ran make test, PostgreSQL failed to start due to insufficient memory. As a result, testing failed.

The problem is because the default effective_cache_size and shared_buffers is was too high for a system with 8 GB of RAM.
After I adjusted parameters manually, PostgreSQL was able to start.

Importance

really want

Proposed implementation

Document the minimum amount of RAM required in the contributing guide.
Possibly adjust effective_cache_size and shared_buffers parameters in the testing environment to allow testing on VMs with 8 GB of RAM.

[vitabaks]

make test runs testing of all possible scenarios, which can be expensive in terms of resources.

Try make molecule-converge, which will create 3 containers and deploy a cluster there, then you can connect to the container if necessary. Next, make molecule-destroy to remove them. I think it's worth updating CONTRIBUTING.md

By default, shared_buffers is set to 25% of the available memory. But you're right, for the test, it's better to redefine to a low value in the local_postgresql_parameters variable in the converge.yml