1# Notify library {#notify} 2 3The notify library implements an event bus, allowing users to register, generate, 4and listen for events. For example, the bdev library may register a new event type 5for bdev creation. Any time a bdev is created, it "sends" the event. Consumers of 6that event may periodically poll for new events to retrieve them. 7The event bus is implemented as a circular ring of fixed size. If event consumers 8do not poll frequently enough, events may be lost. All events are identified by a 9monotonically increasing integer, so missing events may be detected, although 10not recovered. 11 12## Register event types {#notify_register} 13 14During initialization the sender library should register its own event types using 15`spdk_notify_type_register(const char *type)`. Parameter 'type' is the name of 16notification type. 17 18## Get info about events {#notify_get_info} 19 20A consumer can get information about the available event types during runtime using 21`spdk_notify_foreach_type`, which iterates over registered notification types and 22calls a callback on each of them, so that user can produce detailed information 23about notification. 24 25## Get new events {#notify_listen} 26 27A consumer can get events by calling function `spdk_notify_foreach_event`. 28The caller should specify last received event and the maximum number of invocations. 29There might be multiple consumers of each event. The event bus is implemented as a 30circular buffer, so older events may be overwritten by newer ones. 31 32## Send events {#notify_send} 33 34When an event occurs, a library can invoke `spdk_notify_send` with two strings. 35One containing the type of the event, like "spdk_bdev_register", second with context, 36for example "Nvme0n1" 37 38## RPC Calls {#rpc_calls} 39 40See [JSON-RPC documentation](jsonrpc.md/#rpc_notify_get_types) 41