Some Common Exceptions of zuul Forwarding

  springcloud

Order

If zuul is used as api gateway, you will often encounter some exceptions. Here is a summary.

ZuulException

This is the outermost anomaly

public class ZuulException extends Exception {
    public int nStatusCode;
    public String errorCause;

    /**
     * Source Throwable, message, status code and info about the cause
     * @param throwable
     * @param sMessage
     * @param nStatusCode
     * @param errorCause
     */
    public ZuulException(Throwable throwable, String sMessage, int nStatusCode, String errorCause) {
        super(sMessage, throwable);
        this.nStatusCode = nStatusCode;
        this.errorCause = errorCause;
        incrementCounter("ZUUL::EXCEPTION:" + errorCause + ":" + nStatusCode);
    }

    /**
     * error message, status code and info about the cause
     * @param sMessage
     * @param nStatusCode
     * @param errorCause
     */
    public ZuulException(String sMessage, int nStatusCode, String errorCause) {
        super(sMessage);
        this.nStatusCode = nStatusCode;
        this.errorCause = errorCause;
        incrementCounter("ZUUL::EXCEPTION:" + errorCause + ":" + nStatusCode);

    }

    /**
     * Source Throwable,  status code and info about the cause
     * @param throwable
     * @param nStatusCode
     * @param errorCause
     */
    public ZuulException(Throwable throwable, int nStatusCode, String errorCause) {
        super(throwable.getMessage(), throwable);
        this.nStatusCode = nStatusCode;
        this.errorCause = errorCause;
        incrementCounter("ZUUL::EXCEPTION:" + errorCause + ":" + nStatusCode);

    }

    private static final void incrementCounter(String name) {
        CounterFactory.instance().increment(name);
    }

}

RibbonRoutingFilter

spring-cloud-netflix-core-1.2.6.RELEASE-sources.jar! /org/springframework/cloud/netflix/zuul/filters/route/RibbonRoutingFilter.java
This class throws many ZuulException:

@Override
    public Object run() {
        RequestContext context = RequestContext.getCurrentContext();
        this.helper.addIgnoredHeaders();
        try {
            RibbonCommandContext commandContext = buildCommandContext(context);
            ClientHttpResponse response = forward(commandContext);
            setResponse(response);
            return response;
        }
        catch (ZuulException ex) {
            context.set(ERROR_STATUS_CODE, ex.nStatusCode);
            context.set("error.message", ex.errorCause);
            context.set("error.exception", ex);
        }
        catch (Exception ex) {
            context.set("error.status_code",
                    HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            context.set("error.exception", ex);
        }
        return null;
    }

forward

protected ClientHttpResponse forward(RibbonCommandContext context) throws Exception {
        Map<String, Object> info = this.helper.debug(context.getMethod(),
                context.getUri(), context.getHeaders(), context.getParams(),
                context.getRequestEntity());

        RibbonCommand command = this.ribbonCommandFactory.create(context);
        try {
            ClientHttpResponse response = command.execute();
            this.helper.appendDebug(info, response.getStatusCode().value(),
                    response.getHeaders());
            return response;
        }
        catch (HystrixRuntimeException ex) {
            return handleException(info, ex);
        }

    }

Here is a HystrixRuntimeException, mainly related to hystrix, such as timeout.

handleException

protected ClientHttpResponse handleException(Map<String, Object> info,
            HystrixRuntimeException ex) throws ZuulException {
        int statusCode = HttpStatus.INTERNAL_SERVER_ERROR.value();
        Throwable cause = ex;
        String message = ex.getFailureType().toString();

        ClientException clientException = findClientException(ex);
        if (clientException == null) {
            clientException = findClientException(ex.getFallbackException());
        }

        if (clientException != null) {
            if (clientException
                    .getErrorType() == ClientException.ErrorType.SERVER_THROTTLED) {
                statusCode = HttpStatus.SERVICE_UNAVAILABLE.value();
            }
            cause = clientException;
            message = clientException.getErrorType().toString();
        }
        info.put("status", String.valueOf(statusCode));
        throw new ZuulException(cause, "Forwarding error", statusCode, message);
    }

findClientException

protected ClientException findClientException(Throwable t) {
        if (t == null) {
            return null;
        }
        if (t instanceof ClientException) {
            return (ClientException) t;
        }
        return findClientException(t.getCause());
    }

com.netflix.client.ClientException

public class ClientException extends Exception{
    /**
     * 
     */
    private static final long serialVersionUID = -7697654244064441234L;
    
    /**
     * define your error codes here
     * 
     */
    public enum ErrorType{
        GENERAL, 
        CONFIGURATION, 
        NUMBEROF_RETRIES_EXEEDED, 
        NUMBEROF_RETRIES_NEXTSERVER_EXCEEDED, 
        SOCKET_TIMEOUT_EXCEPTION, 
        READ_TIMEOUT_EXCEPTION,
        UNKNOWN_HOST_EXCEPTION,
        CONNECT_EXCEPTION,
        CLIENT_THROTTLED,
        SERVER_THROTTLED,
        NO_ROUTE_TO_HOST_EXCEPTION,
        CACHE_MISSING;
        
        static String getName(int errorCode){
            if (ErrorType.values().length >= errorCode){
                return ErrorType.values()[errorCode].name();
            }else{
                return "UNKNOWN ERROR CODE";
            }
        }
    }
//...
}