前言
1、ThreadLocal是线程变量,线程之间彼此隔离,天生线程安全。因为它是跟着线程走的,考虑到这点,它很适合做链路追踪(TraceId)
2、当我们写的接口接收到其它地方(可能是前端、也可能是其它服务)发来的请求时,此刻,我们的接口所在的服务称作服务端【Server】,而请求方称作客户端【Client】;当我们的接口中再请求其他服务,此刻,我们的接口所在的服务称作客户端【Client】,而被请求方称作客户端【Client】
线程变量承载体
public class TraceIdHolder {
// 初版, 普通的 ThreadLocal, 只适用于不开辟子线程的情况
//private static final ThreadLocal<String> TRACE_ID_HOLDER = new ThreadLocal<>();
// 升级版,new子线程时,为了让线程变量继承,得改用 InheritableThreadLocal
//private static final ThreadLocal<String> TRACE_ID_HOLDER = new InheritableThreadLocal<>();
// 最终版,线程池中开辟线程时,存在线程复用(上个请求使用的线程的线程变量会残留),得改用 TransmittableThreadLocal + TtlExecutors
private static final ThreadLocal<String> TRACE_ID_HOLDER = new TransmittableThreadLocal<>();
public TraceIdHolder() {
}
public static void set(String traceId) {
TRACE_ID_HOLDER.set(traceId);
}
public static String get() {
return TRACE_ID_HOLDER.get();
}
public static String remove() {
String traceId = TRACE_ID_HOLDER.get();
TRACE_ID_HOLDER.remove();
return traceId;
}
}
打印日志
服务端的日志打印很好做,用过滤器Filter即可,每次请求打过来,记录下请求路径、请求头、参数
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.cqf.config.constant.Constant;
import com.cqf.config.wrapper.RequestWrapper;
import com.cqf.threadLocal.TraceIdHolder;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Enumeration;
import java.util.UUID;
@Order(1)
@WebFilter(filterName = "logFilter", urlPatterns = "/*")
public class LogFilter implements Filter {
private static final Logger LOGGER = LoggerFactory.getLogger(LogFilter.class);
private static final String GET = "GET";
private static final String POST = "POST";
private static final String PUT = "PUT";
private static final String DELETE = "DELETE";
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) servletRequest;
String url = request.getRequestURL().toString();
String method = request.getMethod();
Enumeration<String> headerNames = request.getHeaderNames();
String next;
StringBuilder bodyBuffer = new StringBuilder();
boolean hasTraceId = false;
while ((next = headerNames.nextElement()) != null) {
// 过滤掉postman自带的请求头
if (Constant.USELESS_HEADER.contains(next.toLowerCase())) {
continue;
}
String headerValue = request.getHeader(next);
// 每次外部请求过来,在这里设置trace-id
if ("trace-id".equalsIgnoreCase(next) && StringUtils.isNotBlank(headerValue)) {
hasTraceId = true;
TraceIdHolder.set(headerValue);
}
bodyBuffer.append(next).append("=").append(headerValue).append(", ");
}
if (!hasTraceId) {
String traceId = UUID.randomUUID().toString().replace("-", "");
bodyBuffer.append("trace-id").append("=").append(traceId).append(", ");
TraceIdHolder.set(traceId);
}
if (StringUtils.isNotBlank(bodyBuffer.toString())) {
bodyBuffer.delete(bodyBuffer.length() - 2, bodyBuffer.length());
}
RequestWrapper requestWrapper = new RequestWrapper(request);
String bodyString = requestWrapper.getBodyString();
String payload = JSON.toJSONString(JSONObject.parseObject(bodyString),
SerializerFeature.PrettyFormat,
SerializerFeature.WriteMapNullValue,
SerializerFeature.WriteDateUseDateFormat);
// before request
String msg = "[Server] Before request [" +
method +
" uri=" +
url +
"; " +
"headers={" +
bodyBuffer.toString() +
"}]";
if (!GET.equalsIgnoreCase(method)) {
msg = msg + "; payload=" + payload + "]";
}
LOGGER.info(msg);
// 在执行链调用前就要把trace-id放在响应头里
HttpServletResponse response = (HttpServletResponse) servletResponse;
response.setHeader("trace-id", TraceIdHolder.get());
filterChain.doFilter(requestWrapper, servletResponse);
int status = response.getStatus();
// after request
LOGGER.info("[Server] After request, status=" +
status +
" [" +
method +
" uri=" +
url +
"; " +
"headers={" +
bodyBuffer.toString() +
"}]");
}
}
作为客户端时,自己是主动发起方,所以要给RestTemplate设置拦截器,发送请求前打印日志
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.cqf.config.constant.Constant;
import com.cqf.threadLocal.TraceIdHolder;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.HttpHeaders;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
@Configuration
public class WebConfig {
private static final Logger LOGGER = LoggerFactory.getLogger(WebConfig.class);
private final String GET = "GET";
private final String POST = "POST";
private final String PUT = "PUT";
private final String DELETE = "DELETE";
private ClientHttpRequestInterceptor logClientHttpRequestInterceptor() {
return ((httpRequest, body, clientHttpRequestExecution) -> {
// 设置公共请求头
httpRequest.getHeaders().set("trace-id", TraceIdHolder.get());
String methodValue = httpRequest.getMethodValue();
HttpHeaders headers = httpRequest.getHeaders();
String payload = new String(body, 0, body.length, StandardCharsets.UTF_8.name());
StringBuffer buffer = new StringBuffer("");
headers.forEach((key, value) -> {
if (!Constant.USELESS_HEADER.contains(key.toLowerCase())) {
buffer.append(key).append("=").append(value.get(0)).append(", ");
}
});
if (StringUtils.isNotBlank(buffer.toString())) {
buffer.delete(buffer.length() - 2, buffer.length());
}
// 格式化json字符串,方便再日志中查看
payload = JSON.toJSONString(JSONObject.parseObject(payload),
SerializerFeature.PrettyFormat,
SerializerFeature.WriteMapNullValue,
SerializerFeature.WriteDateUseDateFormat);
// before request
String msg = "[Client] Before request [" +
methodValue +
" uri=" +
httpRequest.getURI() +
"; " +
"headers={" +
buffer.toString() + "}";
if (!GET.equalsIgnoreCase(methodValue)) {
msg = msg + "; payload=" + payload;
}
msg += "]";
LOGGER.info(msg);
ClientHttpResponse response = clientHttpRequestExecution.execute(httpRequest, body);
// after request
LOGGER.info("[Client] After request, status=" +
response.getStatusCode().value() +
" [" +
methodValue +
" uri=" +
httpRequest.getURI() +
"; " +
"headers={" +
buffer.toString() +
"}]");
return response;
});
}
@Bean
public RestTemplate restTemplate() {
SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
requestFactory.setConnectTimeout(5000);
requestFactory.setReadTimeout(5000);
RestTemplate restTemplate = new RestTemplate(requestFactory);
// 给RestTemplate 设置拦截器,发送请求前打印日志
ClientHttpRequestInterceptor interceptor = logClientHttpRequestInterceptor();
List<ClientHttpRequestInterceptor> interceptorList = new ArrayList<>();
interceptorList.add(interceptor);
restTemplate.setInterceptors(interceptorList);
return restTemplate;
}
}
Controller的编写
@Resource
private RestTemplate restTemplate;
// 最终版使用,配合TransmittableThreadLocal一起用才生效。线程池需要包装一下。线程数量设置为1是为了发起第二次请求时就能暴露出线程复用带来的问题
private static final ExecutorService executorService = TtlExecutors.getTtlExecutorService(Executors.newFixedThreadPool(1));
@GetMapping("/method1")
public String method1() {
// 初版, 普通的 ThreadLocal, 只适用于不开辟子线程的情况
//restTemplate.exchange("http://localhost:5555/test02", HttpMethod.GET, new HttpEntity<>(null, null), String.class);
// 升级版,new子线程时,为了让线程变量继承,得改用 InheritableThreadLocal
//new Thread(() -> {
// restTemplate.exchange("http://localhost:5555/test02", HttpMethod.GET, new HttpEntity<>(null, null), String.class);
//}).start();
// 最终版,线程池中开辟线程时,存在线程复用(上个请求使用的线程的线程变量会残留),得改用 TransmittableThreadLocal + TtlExecutors
CompletableFuture.runAsync(() -> {
restTemplate.exchange("http://localhost:5555/test02", HttpMethod.GET, new HttpEntity<>(null, null), String.class);
}, executorService);
try { future.get(); } catch (Exception e) { e.printStackTrace(); }
return "1";
}
最终版,postMan连续发送两次请求的日志
总结
初版(ThreadLocal)的缺点:当new新线程时,子线程获取不到父线程的变量,导致trace-id丢失。
于是出现了升级版(InheritableThreadLocal):解决了初版的问题,但是当线程池中开辟线程时,线程复用会残留上一次的trace-id,导致混乱不准。
于是出现了最终版(TransmittableThreadLocal + TtlExecutors)