Customizing Zuul Exception

I have a scenario in Zuul where the service that the URL is routed too might be down . So the reponse body gets thrown with 500 HTTP Status and ZuulException in the JSON body response.

{
  "timestamp": 1459973637928,
  "status": 500,
  "error": "Internal Server Error",
  "exception": "com.netflix.zuul.exception.ZuulException",
  "message": "Forwarding error"
}

All I want to do is to customise or remove the JSON response and maybe change the HTTP status Code.

I tried to create a exception Handler with @ControllerAdvice but the exception is not grabbed by the handler.

UPDATES:

So I extended the Zuul Filter I can see it getting into the run method after the error has been executed how do i change the response then. Below is what i got so far. I read somewhere about SendErrorFilter but how do i implement that and what does it do?

public class CustomFilter extends ZuulFilter {

    @Override
    public String filterType() {
        return "post";
    }

    @Override
    public int filterOrder() {

        return 1;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() {
        final RequestContext ctx = RequestContext.getCurrentContext();
        final HttpServletResponse response = ctx.getResponse();
        if (HttpStatus.INTERNAL_SERVER_ERROR.value() == ctx.getResponse().getStatus()) {
            try {
                response.sendError(404, "Error Error"); //trying to change the response will need to throw a JSON body.
            } catch (final IOException e) {
                e.printStackTrace();
            } ;
        }

        return null;
    }

Added this to the class that has @EnableZuulProxy

@Bean
public CustomFilter customFilter() {
    return new CustomFilter();
}

Solution 1:

We finally got this working [Coded by one of my colleague]:-

public class CustomErrorFilter extends ZuulFilter {

    private static final Logger LOG = LoggerFactory.getLogger(CustomErrorFilter.class);
    @Override
    public String filterType() {
        return "post";
    }

    @Override
    public int filterOrder() {
        return -1; // Needs to run before SendErrorFilter which has filterOrder == 0
    }

    @Override
    public boolean shouldFilter() {
        // only forward to errorPath if it hasn't been forwarded to already
        return RequestContext.getCurrentContext().containsKey("error.status_code");
    }

    @Override
    public Object run() {
        try {
            RequestContext ctx = RequestContext.getCurrentContext();
            Object e = ctx.get("error.exception");

            if (e != null && e instanceof ZuulException) {
                ZuulException zuulException = (ZuulException)e;
                LOG.error("Zuul failure detected: " + zuulException.getMessage(), zuulException);

                // Remove error code to prevent further error handling in follow up filters
                ctx.remove("error.status_code");

                // Populate context with new response values
                ctx.setResponseBody(“Overriding Zuul Exception Body”);
                ctx.getResponse().setContentType("application/json");
                ctx.setResponseStatusCode(500); //Can set any error code as excepted
            }
        }
        catch (Exception ex) {
            LOG.error("Exception filtering in custom error filter", ex);
            ReflectionUtils.rethrowRuntimeException(ex);
        }
        return null;
    }
}

Solution 2:

The Zuul RequestContext doesn't contain the error.exception as mentioned in this answer.
Up to date the Zuul error filter:

@Component
public class ErrorFilter extends ZuulFilter {
    private static final Logger LOG = LoggerFactory.getLogger(ErrorFilter.class);

    private static final String FILTER_TYPE = "error";
    private static final String THROWABLE_KEY = "throwable";
    private static final int FILTER_ORDER = -1;

    @Override
    public String filterType() {
        return FILTER_TYPE;
    }

    @Override
    public int filterOrder() {
        return FILTER_ORDER;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() {
        final RequestContext context = RequestContext.getCurrentContext();
        final Object throwable = context.get(THROWABLE_KEY);

        if (throwable instanceof ZuulException) {
            final ZuulException zuulException = (ZuulException) throwable;
            LOG.error("Zuul failure detected: " + zuulException.getMessage());

            // remove error code to prevent further error handling in follow up filters
            context.remove(THROWABLE_KEY);

            // populate context with new response values
            context.setResponseBody("Overriding Zuul Exception Body");
            context.getResponse().setContentType("application/json");
            // can set any error code as excepted
            context.setResponseStatusCode(503);
        }
        return null;
    }
}

Solution 3:

I had the same problem and was able to solve it in simpler way

Just put this into you Filter run() method

    if (<your condition>) {
        ZuulException zuulException = new ZuulException("User message", statusCode, "Error Details message");
        throw new ZuulRuntimeException(zuulException);
    }

and SendErrorFilter will deliver to the user the message with the desired statusCode.

This Exception in an Exception pattern does not look exactly nice, but it works here.