Graph + Fn: Execute functions as a graph

07b92950
—
Ruben Beltran del Rio
3 years ago

Add Gitlab CI config

e4c7bafd
—
Ruben Beltran del Rio
3 years ago

Initial release

- read-only
- https://git.sr.ht/~rbdr/grafn
- read/write
- git@git.sr.ht:~rbdr/grafn

Graph + Fn: Execute functions as a graph.

Grafn lets you execute sequences of async functions by defining them as vertices in a graph.

This allows you to easily define and manipulate complex dependencies in asynchronous code.

In order to use it you must first create a graph.

```
const Grafn = require('grafn');
const graph = new Grafn();
```

Next you need to add some vertexes.

```
graph.vertex({
name: 'root',
action() {
return 5;
}
});
```

This is a vertex without dependencies, it means it can be executed without waiting for anything else. The return value of this function will be stored so it can be used by its dependents.

You can add dependencies by listing the names as an array in the vertex definition.

```
graph.vertex({
name: 'addition',
dependencies: ['root'],
action(state) {
return state.root + state.root;
}
});
```

Notice how the result of the `root`

vertex is available in this action.

Vertexes will be executed as soon as all of their dependencies are met. For example, consider the following graph

```
const Grafn = require('grafn');
const graph = new Grafn();
graph.vertex({
name: 'root',
action() {
return 5;
}
});
graph.vertex({
name: 'addition',
dependencies: ['root'],
action(state) {
return state.root + state.root;
}
});
graph.vertex({
name: 'subtraction',
dependencies: ['root'],
action(state) {
return state.root - state.root;
}
});
graph.vertex({
name: 'multiplication',
dependencies: ['root'],
action(state) {
return state.root * state.root;
}
});
graph.vertex({
name: 'division',
dependencies: ['root'],
action(state) {
return state.root / state.root;
}
});
graph.vertex({
name: 'tally',
dependencies: ['addition', 'subtraction', 'multiplication', 'division'],
action(state) {
console.log('+', state.addition);
console.log('-', state.subtraction);
console.log('*', state.multiplication);
console.log('/', state.division);
}
});
```

The `addition`

, `subtraction`

, `multiplication`

, and `division`

vertices will
all run as soon as `roott`

is executed. However, the final `tally`

vertex won't
run until all other operations are complete.

You can visualize the graph by using the `graph.toString()`

method. This
will output a graphviz digraph:

```
digraph {
root
addition
root -> addition
subtraction
root -> subtraction
multiplication
root -> multiplication
division
root -> division
tally
addition -> tally
subtraction -> tally
multiplication -> tally
division -> tally
}
```

You can easily change the shape of the graph by changing the dependencies array.

In order to start execution of the graph you should select which node to start from.

```
graph.run('root');
```

After an execution, you can use `graph.toString()`

to check the result of an
execution. It will highlight which nodes were executed successfully (green), and
which nodes threw an error (red).

This project implements the same ideas behind fluorine, a similar graph based library. Grafn wouldn't exist without it.