[IGNITE-12853] ThinClient: Introduce Features for thin clients

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.9
• Component/s: thin client
• Ignite Flags: Docs Required, Release Notes Required
• Assignee: Igor Sapego
• Reporter: Igor Sapego
• Created: 01/Apr/20 16:21
• Updated: 23/Apr/20 10:09
• Resolved: 23/Apr/20 10:09

Description

As we have a lot of different thin clients now, maintained by different people, the issues with our backward compatibility mechanism becomes more and more prominent.

Currently, we use protocol versioning as the only approach to provide backward compatibility. The main issue of this approach is that we can not skip some change in protocol and implement i.e. protocol of version 1.5 without implementation of 1.4. There are many cases when one may want to do so: e.g. when feature provided in 1.4 is not relevant for a specific client, or when protocol version 1.5 contains urgent fix or feature which is easy to implement, but its blocked by not-so-urgent and hard-to-implement feature introduced in 1.4.

So to fix this issue I propose to introduce another backward compatibility mechanism. The idea is to send "supported features" mask by a client to a server, which should be answered with the same mask by the server. The resulting set of enabled features is acquired with a simple logical "AND" operation on these two masks.

This change has many other positive effects:
1. It improves readability and also potentially simplifies debugging.
2. It gives users the ability to enable or disable features of thin clients on both server and client as they desire.

Issue Links

• links to: GitHub Pull Request #7616