Initialization

The initialization method performs various operations to start the publication mechanism.

The initialization method:

Obtains configuration parameters from publisher.xml and establishes communications with subscribers. Access configuration property values by name through the Publisher API.
Provides the Sybase Unified Agent Framework (UAF) interface. Operations Console uses the UAF to provide an agent for each host on which RAP components are installed. The UAF agent works with the Operations Console, receiving commands and requests for component information and configuration. The UAF also forwards requests as needed to each RAP component installed on the host.
Initializes the version constant. Custom feed handlers must identify the version by setting startup.version = PUB_STARTUP_VERSION. This constant tells the Publisher API the version of methods used in the feed handler. Each new version of the Publisher API (but not each version of RAP) increments this constant. Publisher API versioning is designed to simplify migration of custom feed handlers in future versions.
Preallocates message buffers. The Publisher API accepts messages from the feed handler application and forwards them to subscribers. There are two types of buffering: the first is used to buffer messages, thereby saving memory allocation time for each new message; the second is used to resend packets.
Initializes timing services. A timing service is a thread that sleeps or wakes according to an interval timer. To ensure minimal latency of market data messages, this thread notifies a message send service when it is time to send a partially full buffer. The thread also marks intervals for statistics collection.
Initializes the heartbeat mechanism. To facilitate a highly-available configuration, each RAP component must respond to a heartbeat sent by a separate program. The sender of the heartbeat message uses the response (or lack of response) to determine component availability. If necessary, a RAP FAILOVER is invoked. The heartbeat is initialized during pub_initialize() processing.
Initializes statistics. The Publisher API manages statistics on message traffic and reports these statistics to UAF on request.
Initializes the resend infrastructure. If the Publisher API uses multicasting to publish messages, any subscriber can request message resends. The Publisher API caches candidates for resend in a circular buffer.