Evented Scripting Cluster (name subject to change)

This project is an study and attempt to create a replicated cluster of scripts to fire messages on and off.

Features

• Single binary (easy to deploy)
• Senders & Listeners
• Synced key-value store
• Script directory sync
• Lua scripting
• Auto discovery of nodes
• Auto (re)load scripts
• Works on raspberry pi (including zero)
• Plugin system

Soon:

• IPV6 support
• Docker swarm compatible
• Join mode / non-discovery mode

Quick start

Download the proper binary from the releases page:

$ wget https://github.com/diogok/esc/projesc/download/0.0.1/esc-amd64 -O esc

Create a directory for scripts and plugins:

$ mkdir files

Start the program on proper network interface:

$ ./esc -iface wlan0

Repeat on all nodes, edit the scripts on any one of them.

Complete usage

Download the binary from the releases page.

It accepts a configuration file or comand line argumetns (or both with the cli override the file), and comes with sane defaults.

To use the config file pass it as last argument of the command.

node: "mynode"
discovery: 8902
port: 8901
directory: "files"
iface: "eth0"
extras:
  foo: "bar"

You can view the command options:

$ ./esc --help

They are all optional:

$ ./esc --node mynode --port 8901 --discovery 8902 --iface wlan0 --directory myfiles config.yml

Arguments and config are:

• node: Name of this node, defaults to hostname
• discovery: port for auto-discovery of nodes
• port: port for inter node communication
• director: script and plugins directory
• iface: interface to bind to (eth0, wlan0...)

Docker

You can run at each node with docker as:

$ docker run -v /opt/scripts:/scripts -p8901:8901 -p8902:8902 diogok/esc

Or with arguments:

$ docker run -v /opt/scripts:/scripts -p8901:8901 -p8902:8902 diogok/esc -scripts /scripts

Docker swarm compatibility is planned but not supported right now.

Discovery

The project will use mDNS on discovery port to find other nodes, it will connect and disconnect automatically to them.

It will find connect to every esc on the same network.

Messaging

An message is a document with a target, a name and a payload.

Right now it handles only strings as the payload.

Scripting

ESC support running Lua scripts in it's managed environment.

Any script at the configured directory will be executed and reloaded on changes, it will also be kept in sync between nodes.

And example of a script exploring the available functions:

log("I am "..self()) -- this node name, in case you need
log("Foo is "..config("foo")) -- access config extras

-- listen on messages from any node (the first "*") that are named hello
on("*","hello",function(msg)
    log("From "..msg.From.." got "..msg.Name..": "..msg.Payload)
    log("And foo is "..Get("foo"))
end)

-- listen on message clear from nodeb
on(nameOf("nodeb"),"clear",function(msg)
end)

on("*","shutdown",function(msg) 
  -- os and all libs are available
   os.execute("shutdown")
end)

-- Send message to nodeb, could be to everyone with "*"
send("nodeb","blink","led3")

-- Keep a thread going at each 2secs until stopped
tick(2,function()
    i = i + 1
    log("Sending hello "..i)
    send("*","hello","world")
    return i <= 5
    -- if return is true it will loop
end)

Each lua script is an instance on it's own, and can only communicate using messages.

A nice lua guide is at learn X in Y minutes.

Plugin

Plugins are golang programs that extend ESC functions and capabilities.

Every ".so" file found at the configured directory will be loaded as a plugin.

An example plugin is the synced key value store.

License

MIT