The notify library implements an event bus, allowing users to register, generate, and listen for events. For example, the bdev library may register a new event type for bdev creation. Any time a bdev is created, it "sends" the event. Consumers of that event may periodically poll for new events to retrieve them. The event bus is implemented as a circular ring of fixed size. If event consumers do not poll frequently enough, events may be lost. All events are identified by a monotonically increasing integer, so missing events may be detected, although not recovered.
During initialization the sender library should register its own event types using
spdk_notify_type_register(const char *type). Parameter 'type' is the name of notification type.
A consumer can get information about the available event types during runtime using
spdk_notify_foreach_type, which iterates over registered notification types and calls a callback on each of them, so that user can produce detailed information about notification.
A consumer can get events by calling function
spdk_notify_foreach_event. The caller should specify last received event and the maximum number of invocations. There might be multiple consumers of each event. The event bus is implemented as a circular buffer, so older events may be overwritten by newer ones.
When an event occurs, a library can invoke
spdk_notify_send with two strings. One containing the type of the event, like "spdk_bdev_register", second with context, for example "Nvme0n1"