jib以前在给客户讲产品的时候经常提到Oracle Service Bus服务总线适合于短连接，高频率的交易，而不适合那些大报文，然后花费很长的调用时间的应用，前一阵在给客户培训完企业服务总线后，又对OSB的限流机制有了一定了解，事实上，自己的理解也有很多偏差，下面就把在国外看到的一片讲Oracle Service Bus线程机制的文章和大家分享一下吧。
企业服务总线的典型场景
如果我们把pipeline中间的逻辑拉直的话，我们可以看到基本是这个图：
- Request Pipeline:在接收的pipeline中收到请求做处理
- RouteNode:通过路由节点调用业务服务
- Response Pipeline: 处理业务服务的回应，然后将结果返回.(这个图是个特例，具体是判断结果，修改请求，在去调用一个业务服务，然后回送回应)
基本模型
- 在请求pipeline中Oracle Service Bus会启用一个线程(Thread)
- 在调用业务服务的时候，线程释放，回到线程池，同时一个muxer等待回应
- 当回应收到，muxer把接收到的新的请求发送给一个新的线程，并执行response pipeline.
所以
我们可以为Proxy Service和Business Service定义不同的线程池，也就是Proxy Service WorkManager和Business Service WorkManager
没有包含路由节点
如果没有路由节点，OSB仍然会采用另外一个thread处理响应pipeline,但是采用的Default Work Manager
代理服务调用代理服务
同一线程调用Proxy Service的请求Pipeline,同一线程调用Response Pipeline
服务外调
Pipeline处理会block线程直到响应能够异步返回。在进行服务外调的时候，原来的线程不会释放，muxer使用Business Service Work Manager分配一个线程来处理请求，如果大家共享一个work manager,比较容易造成死锁。
总结
- Request Pipeline
- Executes on Proxy Work Manager (WM) Thread so limited by setting of that WM. If no WM specified then uses WLS default WM.
- Route Node
- Request sent using Proxy WM Thread
- Proxy WM Thread is released before getting response
- Muxer is used to handle response
- Muxer hands off response to Business Service (BS) WM
- Response Pipeline
- Executes on Routed Business Service WM Thread so limited by setting of that WM. If no WM specified then uses WLS default WM.
- No Route Node (Echo functionality)
- Proxy WM thread released
- New thread from the default WM used for response pipeline
- Service Callout
- Request sent using proxy pipeline thread
- Proxy thread is suspended (not released) until the response comes back
- Notification of response handled by BS WM thread so limited by setting of that WM. If no WM specified then uses WLS default WM.
- Note this is a very short lived use of the thread
- After notification by callout BS WM thread that thread is released and execution continues on the original pipeline thread.
- Route/Callout to Proxy Service
- Request Pipeline of callee executes on requestor thread
- Response Pipeline of caller executes on response thread of requested proxy
- Throttling
- Request message may be queued if limit reached.
- Requesting thread is released (route node) or suspended (callout)