dynamicTAO

This pages provides a description of the strategies already implemented in TAO as well as the new strategies that are being created.

These strategies will be hooked in the already running ORB in order to modify its behavior.

For a description of how to build new strategies, click here
 

0. Interesting Papers

Alleviating Priority Inversion and Non-determinism in Real-Time CORBA ORB Architectures
 

1. Reactive Strategy

It is also known as the Single Threaded Strategy. When a new connection establishment request arrives, the ORBs Acceptor creates a new Service Handler and registers it with the ORB's reactor. Therefore, there is a single thread taking care of all network requests.

This strategy comes with the standard TAO distribution.
 

2. Thread-per-connection Strategy

When a new connection establishment request arrives, the Acceptor, instead of registering the new Svc_Handler with the ORB's reactor, it creates a new thread which will execute the beforementioned Svc_Handler (in ACE terms, the Svc_Handler is Activated).

This strategy also comes with the standard TAO distribution.

TO-DO:  Both the reactive and the threaded strategies come embedded in the standard TAO distribution. In the future, that will be changed, so all strategies will be implemented outside the ORB, and during initialisation time, one of the strategies (the one used as default) will be hooked.
 
 

2. Thread pool Strategy

This strategy is very similar to the Thread-per-request one. The main difference is that when the strategy is hooked, it spawns a pre-established number of threads, so insted of creating a new thread each time a connection request arrives, one of the threads of the pool is used. This strategy has been designed in such a way that can be easily customized. Below comes a description of all the features offered by this strategy.

Whenever this strategy is hooked, three parameters must be specified:
 

• Pool size: Specifies the number of threads to be spawned.

• Low watermark: This parameter specifies the point (number of threads) at which the pool should be regenerated. When this value is reached, the strategy will automatically spawn Pool_Size - Low_Watermark threads. In order to use a standard thread pool where new threads are never created, the value of this parameter should be set to -1.

• High Watermark: This parameter specifies the point (number of threads) at which threads should be eliminated from the pool. This parameter can be used to bound the maximum number of threads. Because since the pool can be regenerated, a mechanism to establish the upper bound is needed.

Example:

            load_service Concurrency Thread_Pool_Strategy 10 2 10

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