Memory storage

[EltonCN]

Why was it necessary?

This PR implements Memory Storage, a memory synchronization mechanism. It allows the creation of distributed agents between different CST instances/nodes, and the creation of agents using CST-Java and CST-Python simultaneously.

How was it done?

The MemoryStorageCodelet has been implemented. By adding it to the agent, the codelet monitors existing memories and synchronizes them with a Redis server when needed.

Implementation details

In addition to the MemoryStorageCodelet, the MemoryEncoder, which transforms memories to and from Maps with JSON info, and the LamportTime, which implements a logical Lamport clock, were also implemented.

The full communication protocol details is provided in: https://h-iaac.github.io/CST-Python/_build/html/src/Memory%20Storage.html

How to test?

The Tests test communication between local nodes in Java. To run them, you need to have a Redis server available, which has been added to the test CI. If it is not available, the test is skipped.

A test was also implemented to verify the operation of other Memory Storage instances, which at the moment must be executed manually. The test was successfully executed with MS-Python.

Future works

Some more robust memory information encoding and typing system is still needed, allowing objects of arbitrary types to be synchronized.

[codeclimate]

Code Climate has analyzed commit b25903b and detected 6 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Clarity	5
Bug Risk	1

The test coverage on the diff in this pull request is 93.4% (90% is the threshold).

This pull request will bring the total coverage in the repository to 38.0% (1.7% change).

View more on Code Climate.