What is GoJo

GoJo is a Go library created during my bachelor thesis. The library implements Join Patterns as described by Cédric Fournet and Georges Gonthier [1].

Join Patterns allow a declarative description of concurrent programs.

Definitions

• A Join Pattern listens on messages on up to 3 Ports until the Action is executed.
• Pattern Matching is the process of matching messages to a specific Join Pattern.
• An Action is a function that will be executed once a pattern was matched.
• A Port is a Go channel that listens for signals used for Pattern Matching.
• A Signal is sending a message to a Port. A Signal can either be Async or Sync.
  • Async signals are non-blocking and return immediately.
  • Sync signals are blocking and will return a value. An Action sends it's return value to all registered Sync signals.
• A Junction is responsible to keep track of join patterns and registered Signals. A program can consist of multiple Junctions.

Requirements

Go version 1.18 is required to use this library due to the usage of generics.

Usage

To create new Join Patterns and Signals a Junction needs to be created first.

j := junction.NewJunction()

Afterwards, AsyncSignals and SyncSignals can be created through this junction. These functions return two values, a port and a signal. The port is used to register the signals with Join Patterns and signal is the function that can be called to send and receive values from the Join Pattern's action.

port, signal := junction.NewAsyncSignal[<TYPE>](j)

where <TYPE> is the data type of the value sent via the signal.

or

port, signal := junction.NewSyncSignal[<SEND_TYPE>,<RECV_TYPE>](j)

where <SEND_TYPE> is the data type of the Signal to the Join Pattern and <RECV_TYPE> is the data type that will be returned to the signal.

Once Signals are created, they can be used to create new Join Patterns. Join Patterns can listen on up to 3 signals and are not limited to only one synchronous port.

junction.NewBinaryAsyncJoinPattern[<FIRST_TYPE>,<SECOND_TYPE>](portA, portB).Action(func(a <FIRST_TYPE>, b <SECOND_TYPE>) {
  // Add function code here
})

In this example a binary async Join Pattern is created. This means that there exists now a function that will be executed in it's own goroutine once a message was received on both portA and portB. Once messages are received on both ports, the function is executed and receives both messages as the function parameters.

To find more detailed examples, look into the examples folder.

Special Thanks

I want to thank my project's supervisor Dr. Ian Stark. I would not have been able to complete this project without his guidance and help.

References

[1] https://www.microsoft.com/en-us/research/wp-content/uploads/2017/01/join-tutorial.pdf