spring cloud gateway span tagger

RouteIdTaggingGlobalFilter.java

package com.cardinalhealth.connectgateway;

import brave.Span;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.cloud.gateway.route.Route;
import org.springframework.cloud.sleuth.instrument.web.TraceWebFilter;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR;

@Component
public class RouteIdTaggingGlobalFilter implements GlobalFilter {


    /**
     * This is protected in {@link org.springframework.cloud.sleuth.instrument.web.TraceWebFilter} :(
     */
    protected static final String TRACE_REQUEST_ATTR = TraceWebFilter.class.getName()
            + ".TRACE";

    private static final Logger log = LoggerFactory.getLogger(RouteIdTaggingGlobalFilter.class);

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        Object spanObj = exchange.getAttributes().get(TRACE_REQUEST_ATTR);
        if (!(spanObj instanceof Span)) {
            log.info("expected span in exchange attributes, got {}", spanObj);
            return chain.filter(exchange);
        }
        Span span = (Span) spanObj;

        Object routeObj = exchange.getAttributes().get(GATEWAY_ROUTE_ATTR);
        if (!(routeObj instanceof Route)) {
            log.info("expected route in exchange attributes, got {}", routeObj);
            return chain.filter(exchange);
        }
        Route route = (Route) routeObj;

        span.tag("route-id", route.getId());
        return chain.filter(exchange);
    }
}