Chapter 17. Hosting the SQL-NS Execution Engine

IN THIS CHAPTER

• Using the SQL-NS Hosting API

• EngineHost: A Sample Hosting Application

In every example presented in this book so far, the SQL-NS engine runs in a Windows service. To start and stop the engine, you start and stop the service. Although this is adequate in most scenarios, there are cases in which it's desirable to run the SQL-NS engine as an integrated part of a larger application, rather than as a separate service.

To address these cases, SQL-NS provides a Hosting API. This API offers facilities for running the SQL-NS engine within a custom application. When invoked via the Hosting API, the engine and all its subcomponents execute within the hosting application's processno service is involved. The functionality of the engine does not change as a result of being hosted this way. Its behavior (and that of the underlying SQL-NS instance it serves) is the same as when it runs in the Windows service.

Hosting the SQL-NS engine helps integrate SQL-NS functionality into larger applications that provide more than just notification capabilities. Often, such applications already have one or more services (or other processes that run continuously). Hosting the SQL-NS engine may reduce the administrative overhead in these applications: rather than managing the SQL-NS engine separately as a Windows service, it can be embedded in one of the application's existing processes. This chapter explains the SQL-NS Hosting API and shows its use in a sample application.