private void proxyRequestToOrigin() {
        Promise<PooledConnection> promise = null;
        try {
            attemptNum += 1;

            /*
             * Before connecting to the origin, we need to compute how much time we have left for this attempt. This
             * method is also intended to validate deadline and timeouts boundaries for the request as a whole and could
             * throw an exception, skipping the logic below.
             */
            timeLeftForAttempt = originTimeoutManager.computeReadTimeout(zuulRequest, attemptNum);

            currentRequestStat = createRequestStat();
            origin.preRequestChecks(zuulRequest);
            concurrentReqCount.incrementAndGet();

            // update RPS trackers
            updateOriginRpsTrackers(origin, attemptNum);

            // We pass this AtomicReference<Server> here and the origin impl will assign the chosen server to it.
            promise = origin.connectToOrigin(
                    zuulRequest, channelCtx.channel().eventLoop(), attemptNum, passport, chosenServer, chosenHostAddr);

            storeAndLogOriginRequestInfo();
            currentRequestAttempt =
                    origin.newRequestAttempt(chosenServer.get(), chosenHostAddr.get(), context, attemptNum);
            requestAttempts.add(currentRequestAttempt);
            passport.add(PassportState.ORIGIN_CONN_ACQUIRE_START);

            if (promise.isDone()) {
                operationComplete(promise);
            } else {
                promise.addListener(this);
            }
        } catch (Exception ex) {
            if (ex instanceof RequestExpiredException) {
                logger.debug("Request deadline expired while connecting to origin, UUID {}", context.getUUID(), ex);
            } else {
                logger.error("Error while connecting to origin, UUID {}", context.getUUID(), ex);
            }
            storeAndLogOriginRequestInfo();
            if (promise != null && !promise.isDone()) {
                promise.setFailure(ex);
            } else {
                errorFromOrigin(ex);
            }
        }
    }
Get the implementing origin.
<p>
Note: this method gets called in the constructor so if overloading it or any methods called within, you cannot
rely on your own constructor parameters.
zuul-core/src/main/java/com/netflix/zuul/filters/endpoint/ProxyEndpoint.java