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Motivation

According to Changes proposed in IEP-61 we need a group membership/discovery service with likely less strict consistency guarantees than the current Discovery SPI. It is pretty convenient to extract such features to the extra low-level module and provide some API for interaction with the network.There are several problems to have the different interfaces for network communication(DiscoverySPI, CommunicationSPI) including undefined behavior when one port works perfectly while another is not,  duplication of interfaces for sending messages, duplication of the code for network interaction. So for resolving these problems, it is an idea to mix discovery and communication modules into one networking module with one port, API, and implementation allows us to lower requirements for consistency guarantees of membership/discovery protocols. Current Discovery SPI implementations are not scalable enough or rely on external distributed systems (ZooKeeper), so relaxing consistency guarantees and improving scalability is a beneficial goal.

Other goals are:

• Ports unification. Instead of two separate ports for Discovery and Communication subsystems single port should be used for all network interactions. It simplifies overall configuration and eliminates situations of undefined behavior when only one port is available (for discovery or communication) so Ignite node cannot work properly.
• Code base unification. Instead of relying on custom protocols and network code base well known protocols and libraries will be used: SWIM or Rapid-based discovery and membership module and communication part developed on top of netty library.
• API simplification. Bringing all network-related APIs into a single module makes it easier to developers to navigate among network capabilities and find necessary API methods.

Description

Terminology

• endpoint - host(IP)/port which should be configured in discovery configuration. This is the analog 'node' but 'node' is not an appropriate word on such low-level and it represents only host/port rather than the whole node.
• instanceId/setupId - unique identification of every endpoint which should be bounded with a local process(this identification should be generated on every restart). Something like current nodeId but belongs to network endpoint rather than the whole node.
• network member/member - connection + instanceId + messages? It can be used for sending messages. It represents a cluster participant which is able to send or receive some messages.

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