/**
* Copyright 2012 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.netflix.hystrix.contrib.requestservlet;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.netflix.hystrix.HystrixRequestLog;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext;
/**
* Add <code>HystrixRequestLog.getCurrentRequest().getExecutedCommandsAsString()</code> to response as header "X-HystrixLog".
* <p>
* This will not work if the response has been flushed already.
* <p>
* A pre-requisite is that {@link HystrixRequestContext} is initialized, such as by using {@link HystrixRequestContextServletFilter}.
* <p>
* Install by adding the following lines to your project web.xml:
* <p>
*
* <pre>
* {@code
* <filter>
* <display-name>HystrixRequestLogViaResponseHeaderServletFilter</display-name>
* <filter-name>HystrixRequestLogViaResponseHeaderServletFilter</filter-name>
* <filter-class>com.netflix.hystrix.contrib.requestservlet.HystrixRequestLogViaResponseHeaderServletFilter</filter-class>
* </filter>
* <filter-mapping>
* <filter-name>HystrixRequestLogServletFilter</filter-name>
* <url-pattern>/*</url-pattern>
* </filter-mapping>
* }
* </pre>
*/
public class HystrixRequestLogViaResponseHeaderServletFilter implements Filter {
private static final Logger logger = LoggerFactory.getLogger(HystrixRequestLogViaResponseHeaderServletFilter.class);
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
try {
chain.doFilter(request, response);
} finally {
try {
if (HystrixRequestContext.isCurrentThreadInitialized()) {
HystrixRequestLog log = HystrixRequestLog.getCurrentRequest();
if (log != null) {
((HttpServletResponse) response).addHeader("X-HystrixLog", log.getExecutedCommandsAsString());
}
}
} catch (Exception e) {
logger.warn("Unable to append HystrixRequestLog", e);
}
}
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void destroy() {
}
}