gzog

This describes an experimental implementation of a simple protocol for communications between a number of servers (daemons) organized in a full mesh and one or more clients external to the ring.

For historical reasons the daemon is called zog and its Go implementation gzog. There is a client called sprog; its Go implementation is of course gsprog.

Participants send messages, simple strings, to one another using tcp/ip, one of the standard Internet protocols.

Ring

The system runs on a set of five or so machines, each housing a zog daemon listening for messages from the other daemons on port 55551. Servers are connected in a full mesh, seeing other machines as +1, +2, etc on the ring. Each server has to send a keep-alive at least every 300s to keep a connection open.

Daemons log all messages to either access.log or error.log, with CRLF terminated messages of reasonable length (<512 bytes) being logged to access.log and all other messages reported to error.log.

Daemons also listen for traffic from clients on port 55552.

For the purpose of this exercise, the ring consists of five machine with addresses in private address space, 192.168/8

• MV, 192.168.152.242
• PA, 192.168.152.252
• G, 192.168.152.254
• LA, 192.168.152.253
• S, 192.168.152.11

Daemons

TBD

Clients

Clients run gsprog, which talks to the gzog daemons on port 55552. At least one gsprog client will run. By default the client will send messages at configurable intervals to a randomly selected server. Command line switches will be available to change this behavior, to round-robin (-r/--roundRobin) or to target a specific host (-s/--specificHost). If the testing option is chosen, specificHost will be 127.0.0.1.

The default interval should be 10s.

Gzog messages are simple strings, Unicode encoded as UTF-8.

Messages

In this implementation, messages are standard Go strings preceded by a single character, a digit, the wrapping byte.

The wrapping byte will be one of 0, 1, or 2. That is, it will be a single ASCII character, a digit.

Content will be quasi-random with lengths (-i/--interval) in the range [32..63] inclusive, not counting the wrapping byte. Content will consist of printing characters. [Content length should be adjusted as necessary to keep log lines within 80 characters.]

Message Handling

On receiving a message other than a keep-alive from a client, a server will forward it to its +1 and +2 peers with 1 and 2 wrappings respectively.

Daemon-Daemon Messages

On receiving a message from a peer, a server will examine its envelope. All messages will be logged AFTER any forwarding.

If the wrapping is 0 (the digit zero), the message will just be logged. If the wrapping is 1, the message will be forwarded to the peer's +3 server with a zero wrapping. If the wrapping is 2, the message will be forwarded to the +4 server with a zero wrapping.

Client-Daemon Messages

On receiving a message from a client which is other than a keep-alive a server will forward it to its +1 and +2 peers with a 2 wrapping in each case.

If the wrapping is 0 (zero), the message will just be logged.

If the wrapping is 1, the message will be forwarded to the receiver's +1 peer with a zero wrapping. [We will not use this wrapping in the current configuration.]

If the wrapping is 2, the message will be forwarded to the receiver's +2 peer with a zero wrapping.

Protocol

gzog protocol should be org.xlattice.gzog and should at this point define two message pairs: keepAlive and ack, and data and ok.

Project Status

Pre-Alpha.

Licensing

The material on this github.io website is licensed under a Creative Commons Attribution 4.0 International License.

Project software is licensed under an MIT license. Follow the SOFTWARE LICENSE link below for more information on project software licensing.