= Module GraphEngine.Client =

Provides client-side communication instance. In a GraphEngine application, a client is by-default not a communication instance -- for that it does not possess message handling capabilities. GraphEngine.Client extends both the client and the server to support client-side message handling through a single messaging endpoint, while preserving the ability to access the whole memory cloud.

When a client communication instance starts, it connects to the server with a customizable messaging endpoint. The endpoint should implement the interface IMessagePassingEndpoint, but is not limited to using native Trinity protocol. Therefore we could implement the interface with any messaging transport, e.g. WCF, gRPC etc. Once the endpoint establishes connection, the client registers itself at the destination server with a randomly generated cookie. The server keeps track of the connected clients, and assigns a TTL value to each client. The server does not initiate new connections to the clients, but rather, responds to client-side polling. New client-going messages are first queued at the server, and piggybacked during polling. This allows a client to send asynchronous messages, without being blocked by a single request/response pair on the endpoint.

This module also implements MemoryCloud for both client and server. The server side uses HostedMemoryCloud: FixedMemoryCloud and provides aforementioned client-registration services. The client side uses ClientMemoryCloud: MemoryCloud, which takes a single message passing endpoint (rather than connecting to every remote storage in the cluster), and send all messages as redirected messages, and all key-value store operations as custom remote calls, which are handled in TrinityClientModule.