docs: Describe implementation of remote interface

docs/remote-interface.md

@@ -0,0 +1,67 @@
+# Remote interface
+## Introduction
+
+```
+ +-----------------------------------------------+
+ |               remote interface                |
+ |    +----------------------------------------+ | 
+ |   +----------------------------------------+| |
+ |  +----------------------------------------+|+ |
+ |  |     RabbitMQ-provided RPC              |+  |
+ |  +----------------------------------------+   |
+ |            |                     ^            |
+ +------------|---------------------|------------+
+ +------------|---------------------|------------+
+ |            |   RabbitMQ broker   |            |
+ |            |                     |            |
+ |            |             +------------------+ |
+ |            v            +------------------+| |
+ |  +------------------+  +------------------+|| |
+ |  | incoming queue   |  | private queue    ||| |
+ |  |                  |  |                  ||| |
+ |  | - trytes         |  | - PoW result     ||| |
+ |  | - mwm            |  |                  ||+ |
+ |  |                  |  |                  |+  |
+ |  +------------------+  +------------------+   |
+ |            |                     ^            |
+ +------------|---------------------|------------+
+              v                     |
+   +---------------------------------------------+
+  +---------------------------------------------+|
+ +---------------------------------------------+|+
+ |                  remote worker              |+
+ +---------------------------------------------+
+```
+To support asynchronouse remote procedure call, remote interface, `Remote_ImplContext`, in dcurl provides an interface to implement it. dcurl currently uses RabbitMQ C client to implement asynchronouse RPC in remote interface. Remote interface provides thread management to can run an asynchronouse RPC per thread.
+
+Here are detailed implementations of the RabbitMQ-provided RPC pattern as follows:
+* Asynchronouse RPC requests are inserted into the message queue, `incoming_queue`, in RabbitMQ broker 
+* Asynchronouse RPCs with exclusive private queues (callback queues) with TTL = 10s property
+* Correlation ID is not used
+* An asynchronouse RPC uses a connection to RabbitMQ broker
+* Remote workers can obtain requests from `incoming_queue` by default exchange of RabbitMQ broker 
+
+## How to test remote interface in localhost
+You need to open three terminals
+
+Terminal 1: Run the RabbitMQ broker You can quickly use docker to run the RabbitMQ broker, rabbitmq
+```
+$ sudo docker run -d rabbitmq
+```
+
+Terminal 2: Run remote workers
+```
+$ ./build/remote-worker
+```
+How to build remote worker on FPGA board
+```
+$ make BUILD_REMOTE=1 BUILD_FPGA_ACCEL=1 BOARD=de10nano
+```
+
+Terminal 3: Run check
+```
+$ make BUILD_REMOTE=1 BUILD_DEBUG=1 check
+```
+
+## Requirements
+Remote interface requires RabbitMQ broker