public void errorFromOrigin(Throwable ex) {
        try {
            // Flag that there was an origin server related error for the loadbalancer to choose
            // whether to circuit-trip this server.
            if (originConn != null) {
                // NOTE: if originConn is null, then these stats will have been incremented within
                // PerServerConnectionPool
                // so don't need to be here.
                originConn.getServer().incrementSuccessiveConnectionFailureCount();
                originConn.getServer().addToFailureCount();

                originConn.flagShouldClose();
            }

            // detach from current origin
            Channel originCh = unlinkFromOrigin();

            methodBinding.bind(() -> processErrorFromOrigin(ex, originCh));
        } catch (Exception e) {
            channelCtx.fireExceptionCaught(ex);
        }
    }
Override to track your own request stats.
zuul-core/src/main/java/com/netflix/zuul/filters/endpoint/ProxyEndpoint.java