Event Service

The Event Service provides standard event service facilities for the distribution of ECSP events to external clients. It comprises Event Logging and Event Notification services.

Event Logger

The Event Logger provides the necessary services for the logging of ECSP events to hard store. All events are logged to a disk-based FIFO to be retrieved on demand.

The Event Logger task is implemented as a single process comprising of two cooperating threads:

The main thread comprises a standard message receive loop for processing requests from other tasks (for example to request a log retrieval or to accept and event for logging to disk);
A second thread is responsible for performing event retrievals from disk.

The log file is a fixed size but variable record length FIFO file. It is created when the task is first initialised and also on any subsequence restart if the current file appears to be missing or corrupt.

Event Notifier

The Event Notification task provides the necessary services for both raising and receiving event notifications on any single Element Processor Unit (EPU) or Communications Processor Unit (CPU). It accepts new events from client tasks for publishing into the system and publishes accepted events to all tasks which have registered an interest.

New notifications are introduced into the system by means of a client ‘publishing’ a notification by creating a new event. This notification is then, in turn, passed to each ‘subscriber’ – a subscriber having previously expressed an interest in the particular class of notification.

The Event Notification task is implemented as a single, message driven, process comprising of two cooperating threads:

The first thread comprises of a standard message receive loop for processing requests from other tasks (for example to publish an event or update a subscribers information);
The second thread is responsible for actually forwarding the notifications to interested tasks.

The Event Notification task communicates with many tasks within the ECSP in order to publish event notifications to the tasks that have requested such notification.
Client tasks may request the Event Notification task to add them to, or remove them from, the subscription lists associated with each class of event. Client tasks may also request the Event Notification task to publish a new notification.

The two threads comprising the Event Notification task operate independently of each other.

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