AsyncSteps timeout & cancel

Execution of AsyncSteps “thread” can be canceled only through .cancel() API on root AsyncSteps object.

Such requirement is intentional design as normal abort must occur through .error() with regular stack unwinding.

The difference in stack unwinding is that both cases do call cancel handlers, but only the later calls error handlers.

const root_as = $as().add( (asi) => {/*...*/} ).execute();
setTimeout( () => root_as.cancel(), 1e3 ); // cancel in 1 second

Cancel handlers

Cancel handler are set through asi.setCancel() API during step execution.

Cancel handlers are called BEFORE error handlers and ONLY during stack unwinding due to cancel or error.

asi.add( (asi) => {
    asi.setCancel( (asi) => do_some_cleanup() );
    // note that explicit success() or sub-step is required
    setTimeout( () => asi.success(), 1e3 );
} );


Timeouts are set per step and they cover all inner sub-steps. If timeout is reached then Timeout error is thrown.

AsyncSteps timeout is effective control of maximum execution time.

    (asi) => {
        asi.setTimeout( 10e3 ); // set 10 second
        asi.setTimeout( 1e3 ); // override with 1 second
        // note that explicit success() or sub-step is required
        asi.add( (asi) => {
            asi.setTimeout( 100e3 ); // only applies to sub-step
        } );
    (asi, error_code) => {
        // Note that timeout gets triggered after 1 second, but not 100!
        if (error_code === 'Timeout') {

Cancel & Timeout side effects

If setCancel() or setTimeout() is called then it disables implicit success() at end of step.