Queue

The queue folder contains a multi-producer single-consumer queue implementation, which is composed of a non-templated base class and a generic templated class. This queue will be unique to each cluster in the middleware system, and will be used to store MiddlewareMessage objects. The queue must be declared with a QueueTraits type, which is a templated structure that contains the following members:

• T - the type that will be contained in the queue

• LockStrategy - a type that will be used to lock a mutex with a RAII pattern.

• MutexType - the mutex type, that must be of QueueMutex type, which can only be instantiated as pointer or integer type.

• ELEMENT_COUNT - the number of elements that the queue can store.

Before using the queue, it is mandatory to first call the init method, otherwise it may lead to undefined behaviour. Afterwards, to write and read from the queue, two nested classes named Sender and Receiver are provided, each receiving a reference to a queue object. To write an element to the queue, simply call the method write of the Sender nested class. To read an element from the queue, call peek, and then advance from the Receiver nested class. The call to advance is needed in order for the queue to advance to the next written element.

Each queue will also contain statistics that are stored in a structure named QueueStats. Each time a queue will be processed, you can call the queue’s takeSnapshot method to internally update some of these statistics like the maximum fill rate. Other statistics, such as processed messages or lost messages, are updated during read and write operations.