motan學習筆記 五 opentracing學習入門

motan學習筆記 一 微博輕量級RPC框架Motan

motan學習筆記 二 motan架構分析

motan學習筆記 三 motan Demo 分析

motan學習筆記 四 motan Demo 之yar 分析

motan學習筆記 五 opentracing學習入門

motan學習筆記 六 opentracing Brave+zipkin實現

opentracing是什麼？

opentracing(http://opentracing.io/)  是分佈式跟蹤系統，當我們把系統拆成服務化，分佈式系統的時候，查詢一個問題，很可能需要多個登錄多臺機器。

opentracing 定義了一套api

通過提供平臺無關、廠商無關的API，使得開發人員能夠方便的添加（或更換）追蹤系統的實現。OpenTracing正在爲全球的分佈式追蹤，提供統一的概念和數據標準。

opentracing 在哪裏有java版？

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

從下面的圖，可以看出api爲定義模塊，mock擋板 noop空實現  impl具體實現

opentracing 定義了哪些api?

span

一條消息，相當於一個打點信息，裏面有兩個重要的方法  finish 和 其他

finish 用來完成span的信息，並且用於提交 而其他方法用來組裝span的數據

SpanContext

及傳輸的上下文，保存一些數據，一般loaclThread的，主要方法

Iterable<Map.Entry<String, String>> baggageItems();

Tracer

定義了兩個方法,一個是往spancontext 插入參數，一個獲取spancontext，相當於span集合

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

Format其實就是 定義的幾個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

顧名思義，builder模式，用來構建 span, 關鍵是start方法，構建成功

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();

  }