protected final AtomicInteger getRunningFilterIndex(I zuulMesg) {
        SessionContext ctx = zuulMesg.getContext();
        return (AtomicInteger)
                Preconditions.checkNotNull(ctx.get(RUNNING_FILTER_IDX_SESSION_CTX_KEY), "runningFilterIndex");
    }
Subclasses of this class are supposed to be thread safe

Created by saroskar on 5/18/17.
zuul-core/src/main/java/com/netflix/zuul/netty/filter/BaseZuulFilterRunner.java