plastic-io

Executions, budgets and cancellation (2.1)

url() now resolves when the execution has ended: every set function and every connector delivery it started has settled, or its budget ran out, or it was cancelled. invoke() returns the handle behind that promise.

const handle = scheduler.invoke("index", value, "field", undefined, {
    budget: {wallMs: 5000, hops: 10000, fanOut: 1000, depth: 256},
});
handle.cancel("user pressed stop");        // cooperative: refused at the next hop
const result = await handle.done;          // never rejects
// result: {state: "completed" | "failed" | "cancelled" | "abandoned", reason, hops, errors, duration, budget}

• Every event carries executionId, seq, and for edge-level events spanId and parentSpanId, so a run can be reconstructed from its events.
• end fires once per execution, last. endedge fires when the node's set function has finished, so afterSet now precedes it. afterSet carries err when the set function failed.
• Running out of budget emits one error with code: "BUDGET_EXCEEDED" and cancels the execution (reason: "budget:<dimension>"). A cancellation that cannot drain within graceMs (250 ms) ends as abandoned.
• A node that emits on an edge after its execution has ended (a UI event, a timer) starts a new execution with trigger: "edge" and parentExecutionId on its begin event.
• Node code receives a host binding: host.executionId, host.cancelled, host.signal (an AbortSignal for fetch), host.throwIfCancelled(), host.emit(kind, data) (an observation event, counted against the budget), host.now(), host.random(), plus whatever the embedder adds through new Scheduler(graph, context, state, logger, {host}).
• Set functions are compiled from their source as written (AsyncFunction), so top-level await and modern syntax work; {compile: "meriyah"} keeps the 2.0 parse-and-regenerate path. Compiled functions are cached per scheduler.
• onInput / onOutput hooks validate values entering and leaving nodes; a thrown error is a CONTRACT_VIOLATION warning, or an error that drops the delivery with {contractMode: "reject"}.
• A connector into another graph loads that graph for itself; 2.0 redirected the node's remaining connectors into it.
• scheduler.cancelAll(reason) ends every open execution, for embedders that replace the graph while it runs.

Graph scheduling engine.

This program can execute graphs written in the application/json+plastic-io schema.

Documentation

Test Coverage

Repo

Major engine features

• Just in time loading and compiling of:
  • graph
  • nodes
  • embedded graphs
  • ES6 code
• Event emitter shows detailed graph execution data
• Graphs can be published, linked and embedded in other graphs
• Nodes can be published and linked
• Graphs support templating engines to create UIs using various frameworks (e.g.: Vue, React)

Basic Usage

    // load the lib
    import {Scheduler} from "plastic-io";
    // instantiate the scheduler
    const scheduler = new Scheduler(myGraphJson);
    scheduler.url("url-of-a-node", "some value");

For more useage see Scheduler

To create, run and debug graphs, use the plastic-io/graph-editor and the plastic-io/graph-server