Function inflightRequestThrottle

lib/plugins/inflightRequestThrottle.js:38–74

* The `inflightRequestThrottle` module allows you to specify an upper limit to * the maximum number of inflight requests your server is able to handle. This * is a simple heuristic for protecting against event loop contention between * requests causing unacceptable latencies. * * The custom err

(opts)

 * server.pre(restify.plugins.inflightRequestThrottle(options));
 */
function inflightRequestThrottle(opts) {
    // Scrub input and populate our configuration
    assert.object(opts, 'opts');
    assert.number(opts.limit, 'opts.limit');
    assert.object(opts.server, 'opts.server');
    assert.func(opts.server.inflightRequests, 'opts.server.inflightRequests');

    if (opts.err !== undefined && opts.err !== null) {
        assert.ok(opts.err instanceof Error, 'opts.err must be an error');
        assert.optionalNumber(opts.err.statusCode, 'opts.err.statusCode');
    }

    var plugin = {};
    plugin._err = opts.err || new ServiceUnavailableError('resource exhausted');
    plugin._limit = opts.limit;
    plugin._server = opts.server;

    function onRequest(req, res, next) {
        var inflightRequests = plugin._server.inflightRequests();

        if (inflightRequests > plugin._limit) {
            req.log.trace(
                {
                    plugin: 'inflightRequestThrottle',
                    inflightRequests: inflightRequests,
                    limit: plugin._limit
                },
                'maximum inflight requests exceeded, rejecting request'
            );
            return next(plugin._err);
        }

        return next();
    }

    return onRequest;
}

module.exports = inflightRequestThrottle;