Sleuth

港控/mmm° 2022-03-21 14:48 237阅读 0赞

### 文章目录 ###

*  原理介绍
 *  Brave和Zipkin
 *  使用
 *   *  依赖
     *  Sleuth对feign的支持
     *  Sleuth对RestTemplate的支持
     *  Sleuth对多线程的支持

# 原理介绍 #

Sleuth通过Trace定义一次业务调用链，根据它的信息，我们就知道多少个系统参与了该业务处理。  
Span用来记录系统间的调用顺序和时间戳信息。  
Trace和Span的信息经过整合，就能知道该业务的完整调用链。

# Brave和Zipkin #

Brave是一个用于捕捉分布式系统之间调用信息的工具库，然后将这些信息以Span的形式发送给Zipkin。  
参考：[https://github.com/openzipkin/brave][https_github.com_openzipkin_brave]

从2.0.0版本开始，Sleuth不再自己存储上下文信息，而是使用Brave作为调用链工具库，并且遵循Brave的命名和标记惯例。

如果你想延用老版本的使用方式，可以配置`spring.sleuth.http.legacy.enabled=true`。

Zipkin是一个基于Google Dapper论文设计的分布式跟踪系统，它收集系统的`延时数据`并提供展示界面，以便用户排查问题。  
参考：[https://github.com/openzipkin/zipkin][https_github.com_openzipkin_zipkin]

Zipkin启动方式

*  java -jar zipkin.jar
 *  还支持源码部署和Docker镜像启动。
 *  Zipkin支持各种持久化方式，默认存储在内存中
 *  部署后，默认的启动端口位9411，[http://localhost:9411/][http_localhost_9411]

# 使用 #

引入`spring-cloud-starter-sleuth`依赖之后，我们的日志组件可以自动打印Span信息。可以随着feign、restTemplate往服务端传递，也可以在父子线程间传递。

## 依赖 ##

<dependency>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-starter-sleuth</artifactId>
    </dependency>
    
    
    <dependency>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
    
    
    <dependency>
    	<groupId>org.springframework.boot</groupId>
    	<artifactId>spring-boot-starter-web</artifactId>
    </dependency>

## Sleuth对feign的支持 ##

*  Feign提供了feign.Client接口以便开发者自定义远程调用功能。
 *  Sleuth使用了TracingFeignClient实现Feign接口，在Http调用前，在Header中添加Span信息。

public Response execute(Request request, Options options) throws IOException { 
        Map<String, Collection<String>> headers = new HashMap(request.headers());
        Span span = this.handleSend(headers, request, (Span)null);
        if (log.isDebugEnabled()) { 
            log.debug("Handled send of " + span);
        }
    
        Response response = null;
        IOException error = null;
    
        Object var9;
        try { 
            SpanInScope ws = this.tracer.withSpanInScope(span);
            Throwable var8 = null;
    
            try { 
                var9 = response = this.delegate.execute(this.modifiedRequest(request, headers), options);
            } catch (Throwable var27) { 
                var9 = var27;
                var8 = var27;
                throw var27;
            } finally { 
                if (ws != null) { 
                    if (var8 != null) { 
                        try { 
                            ws.close();
                        } catch (Throwable var26) { 
                            var8.addSuppressed(var26);
                        }
                    } else { 
                        ws.close();
                    }
                }
    
            }
        } catch (RuntimeException | Error | IOException var29) { 
            error = var29;
            throw var29;
        } finally { 
            this.handleReceive(span, response, error);
            if (log.isDebugEnabled()) { 
                log.debug("Handled receive of " + span);
            }
    
        }
    
        return (Response)var9;
    }

## Sleuth对RestTemplate的支持 ##

对RestTemplate的支持并不是临时初始化的，需要将RestTemplate注册成一个Bean。

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    package brave.spring.web;
    
    import brave.Span;
    import brave.Tracer;
    import brave.Tracing;
    import brave.Tracer.SpanInScope;
    import brave.http.HttpClientAdapter;
    import brave.http.HttpClientHandler;
    import brave.http.HttpTracing;
    import brave.propagation.Propagation.Setter;
    import brave.propagation.TraceContext.Injector;
    import java.io.IOException;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.http.HttpHeaders;
    import org.springframework.http.HttpRequest;
    import org.springframework.http.client.ClientHttpRequestExecution;
    import org.springframework.http.client.ClientHttpRequestInterceptor;
    import org.springframework.http.client.ClientHttpResponse;
    
    public final class TracingClientHttpRequestInterceptor implements ClientHttpRequestInterceptor { 
        static final Setter<HttpHeaders, String> SETTER = new Setter<HttpHeaders, String>() { 
            public void put(HttpHeaders carrier, String key, String value) { 
                carrier.set(key, value);
            }
    
            public String toString() { 
                return "HttpHeaders::set";
            }
        };
        final Tracer tracer;
        final HttpClientHandler<HttpRequest, ClientHttpResponse> handler;
        final Injector<HttpHeaders> injector;
    
        public static ClientHttpRequestInterceptor create(Tracing tracing) { 
            return create(HttpTracing.create(tracing));
        }
    
        public static ClientHttpRequestInterceptor create(HttpTracing httpTracing) { 
            return new TracingClientHttpRequestInterceptor(httpTracing);
        }
    
        @Autowired
        TracingClientHttpRequestInterceptor(HttpTracing httpTracing) { 
            this.tracer = httpTracing.tracing().tracer();
            this.handler = HttpClientHandler.create(httpTracing, new TracingClientHttpRequestInterceptor.HttpAdapter());
            this.injector = httpTracing.tracing().propagation().injector(SETTER);
        }
    
        public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException { 
            Span span = this.handler.handleSend(this.injector, request.getHeaders(), request);
            ClientHttpResponse response = null;
            IOException error = null;
    
            Object var9;
            try { 
                SpanInScope ws = this.tracer.withSpanInScope(span);
                Throwable var8 = null;
    
                try { 
                    var9 = response = execution.execute(request, body);
                } catch (Throwable var27) { 
                    var9 = var27;
                    var8 = var27;
                    throw var27;
                } finally { 
                    if (ws != null) { 
                        if (var8 != null) { 
                            try { 
                                ws.close();
                            } catch (Throwable var26) { 
                            }
                        } else { 
                            ws.close();
                        }
                    }
    
                }
            } catch (RuntimeException | Error | IOException var29) { 
                error = var29;
                throw var29;
            } finally { 
                this.handler.handleReceive(response, error, span);
            }
    
            return (ClientHttpResponse)var9;
        }
    
        static final class HttpAdapter extends HttpClientAdapter<HttpRequest, ClientHttpResponse> { 
            HttpAdapter() { 
            }
    
            public String method(HttpRequest request) { 
                return request.getMethod().name();
            }
    
            public String url(HttpRequest request) { 
                return request.getURI().toString();
            }
    
            public String requestHeader(HttpRequest request, String name) { 
                Object result = request.getHeaders().getFirst(name);
                return result != null ? result.toString() : "";
            }
    
            public Integer statusCode(ClientHttpResponse response) { 
                try { 
                    return response.getRawStatusCode();
                } catch (IOException var3) { 
                    return null;
                }
            }
        }
    }

## Sleuth对多线程的支持 ##

Sleuth提供了三种多线程实现

*  LazyTraceExecutor
 *  TraceableExecutorService
 *  TraceableScheduleExecutorService  
    它们可以在创建新的任务时新建一个Span。  
    `必须使用这三种多线程实现才有效。`

[https_github.com_openzipkin_brave]: https://github.com/openzipkin/brave
[https_github.com_openzipkin_zipkin]: https://github.com/openzipkin/zipkin
[http_localhost_9411]: http://localhost:9411/