motan学习笔记 五 opentracing学习入门

motan学习笔记 一 微博轻量级RPC框架Motan

motan学习笔记 二 motan架构分析

motan学习笔记 三 motan Demo 分析

motan学习笔记 四 motan Demo 之yar 分析

motan学习笔记 五 opentracing学习入门

motan学习笔记 六 opentracing Brave+zipkin实现

opentracing是什么？

opentracing(http://opentracing.io/)  是分布式跟踪系统，当我们把系统拆成服务化，分布式系统的时候，查询一个问题，很可能需要多个登录多台机器。
opentracing 定义了一套api
通过提供平台无关、厂商无关的API，使得开发人员能够方便的添加（或更换）追踪系统的实现。OpenTracing正在为全球的分布式追踪，提供统一的概念和数据标准。

opentracing 在哪里有java版？

从github，下载java版本的分支(https://github.com/opentracing/opentracing-java)

从下面的图，可以看出api为定义模块，mock挡板 noop空实现  impl具体实现

opentracing 定义了哪些api?

span

一条消息，相当于一个打点信息，里面有两个重要的方法  finish 和 其他

finish 用来完成span的信息，并且用于提交 而其他方法用来组装span的数据

SpanContext

及传输的上下文，保存一些数据，一般loaclThread的，主要方法
Iterable<Map.Entry<String, String>> baggageItems();

Tracer

定义了两个方法,一个是往spancontext 插入参数，一个获取spancontext，相当于span集合

<C> void inject(SpanContext spanContext, Format<C> format, C carrier);
<C> SpanContext extract(Format<C> format, C carrier);

Format其实就是 定义的几个map  

public interface Format<C> {
final class Builtin<C> implements Format<C> {
public final static Format<TextMap> TEXT_MAP = new Builtin<TextMap>();
public final static Format<TextMap> HTTP_HEADERS = new Builtin<TextMap>();
public final static Format<ByteBuffer> BINARY = new Builtin<ByteBuffer>();
}

SpanBuilder

顾名思义，builder模式，用来构建 span, 关键是start方法，构建成功

interface SpanBuilder extends SpanContext {

/**
* A shorthand for addReference(References.CHILD_OF, parent).
*/
SpanBuilder asChildOf(SpanContext parent);

/**
* A shorthand for addReference(References.CHILD_OF, parent.context()).
*/
SpanBuilder asChildOf(Span parent);

/**
* Add a reference from the Span being built to a distinct (usually parent) Span. May be called multiple times to
* represent multiple such References.
*
* @param referenceType the reference type, typically one of the constants defined in References
* @param referencedContext the SpanContext being referenced; e.g., for a References.CHILD_OF referenceType, the
*                          referencedContext is the parent
*
* @see io.opentracing.References
*/
SpanBuilder addReference(String referenceType, SpanContext referencedContext);

/** Same as {@link Span#setTag(String, String)}, but for the span being built. */
SpanBuilder withTag(String key, String value);

/** Same as {@link Span#setTag(String, String)}, but for the span being built. */
SpanBuilder withTag(String key, boolean value);

/** Same as {@link Span#setTag(String, String)}, but for the span being built. */
SpanBuilder withTag(String key, Number value);

/** Specify a timestamp of when the Span was started, represented in microseconds since epoch. */
SpanBuilder withStartTimestamp(long microseconds);

/** Returns the started Span. */
Span start();

}