Yogurt.cloud

Design

We design our service call and data tran

Messages

All messages will be sent through UDP.

Every service call contain 3 messages.

• Request
• Response
• ACK Response

All messages have a shared format as below.

• Call ID: A unique 2 byte ID for a service call.

• EOM: Indicating if the packet is the last packet for a message.

• ACK: Indicating if the message is pure ACK, i.e. no need to ACK again.

• Packet ID: A 4 byte integer representing the fragment ID for current message.

• ACK Packet ID: Next packet expected from sender, for replying message only.

• Packet Body: Data in the packet.

        0                   1                   2                   3   
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                               |E|A|                           |
       |            Call ID            |O|C|         Reserved          |
       |                               |M|K|                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           Packet ID                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         ACK Packet ID                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    
                                   Header Format
  

A packet with EOM flag set is considered to be the last packet of the message. Receiving such packet means that the whole message has been transfered.

The server will buffer the response after receiving a request unless receiving ACK response or a ACK timeout.

Packet Body Format

The beginning part of the packet will be headers, encoded in ASCII text. After the header, there will be an empty line, followed by message body.

The format of header is described as below.

First line:

<API-VERSION> <MESSAGE-TYPE> <ARGUMENT*>

For examples:

# For Request
YC1 GET /path/to/file.txt
YC1 INSERT /path/to/file.txt
YC1 MONITOR /path/to/file.txt
YC1 DELETE /path/to/file.txt
YC1 CHECK /path/to/file.txt

# For Response
YC1 STATUS SUCCESS
YC1 STATUS ERROR
YC1 NOTICE

For remaining headers, they will be key-value pairs represented in the following format.

<key>: <value>
# Example
Offset: 0
Limit: 10

Service Request Message

Request a File

Request:

YC1 READ /path/to/file.txt
Offset: 2  # Offset in bytes default to 0
Limit: 5  # Maximum bytes returned in bytes

Response:

Success

RC1 STATUS SUCCESS

File content in binary

Error

RC1 STATUS ERROR
Exception: 404 File Not Found

Insert into a file

Request:

YC1 INSERT /path/to/file.txt
Offset: 5

Content in binary

Response:

Success / ERROR

Monitor a file

Request:

YC1 MONITOR /path/to/file.txt
Interval: 3600  # Time in seconds that the client want to listen to the server.

Response:

YC1 NOTICE

New file content in binary.

How to run against proxy

Run Proxy

cd node
npm install
npm run app

Run Server

./java/scripts/run_server.sh

Run Client

./java/scripts/run_client_proxy.sh