Caf.js

Co-design cloud assistants with your web app and IoT devices.

See https://www.cafjs.com

Caf.js library to delay method invocation

Queues methods to be executed some time in the future.

Sets periodic method invocations that could continue until cancelled, or when they reach a fixed number of completions.

API

See {@link module:caf_delay/proxy_delay}.

An example that calls the method __ca_increment__ periodically (just for nTimes).

exports.methods = {
    ...
    async scheduleRepeat(delay, delta, interval, nTimes) {
        const repeater = this.$.delay.newRepeater(interval, nTimes);
        const id = this.$.delay.scheduleWithOffset(
            delay, '__ca_increment__', [delta], repeater, true
        );
        return [null, id];
    },
    async cancel(id) {
        this.$.delay.cancel(id);
        return this.getState();
    },
    async getPending() {
        return [null, this.$.delay.getPending()];
    }
    async __ca_increment__(delta, id) {
        this.$.log.debug(`inc delta:${delta} id:${id}`);
        this.state.counter = this.state.counter + delta;
        return [];
    },
    ...

The arguments delay and interval are in seconds, and they represent the time before the first __ca_increment__() invocation, and the time between invocations after that. Instead of a time offset, we can also trigger actions with UTC time with schedule().

The last true argument to scheduleWithOffset() ensures that an id identifying the scheduled task is the last argument to __ca_increment__. This id was also returned by scheduleWithOffset(), and can be used to cancel pending actions.

To query the status of scheduled actions for this CA use getPending().

There are no guarantees that methods execute exactly the required number of times, or timely. Really late tasks can be ignored by setting ignoreAfterInSec (defaults to 24 hours), otherwise they will eventually execute at least once.

The internal cron checks for ready tasks every delayIntervalCheckInSec, and this defaults to once a second, setting a practical minimum for time resolution.

Configuration

framework.json

See {@link module:caf_delay/plug_delay}

ca.json

See {@link module:caf_delay/plug_ca_delay}