DaemonApp unit

Daemon (service) application class.

The daemonapp unit implements a TApplication class which encapsulates a daemon or service application. It handles installation where this is necessary, and does instantiation of the various daemons where necessary.

The unit consists of 3 separate classes which cooperate tightly:

TDaemon: This is a class that implements the daemon's functionality. One or more descendents of this class can be implemented and instantiated in a single daemon application. For more information, see TDaemon.
TDaemonApplication: This is the actual daemon application class. A global instance of this class is instantiated. It handles the command-line arguments, and instantiates the various daemons. For more information, see TDaemonApplication.
TDaemonDef: This class defines the daemon in the operation system. The TDaemonApplication class has a collection of TDaemonDef instances, which it uses to start the various daemons. For more information, see TDaemonDef.

As can be seen, a single application can implement one ore more daemons (services). Each daemon will be run in a separate thread which is controlled by the application class.

The classes take care of logging through the TEventLog class.

Many options are needed only to make the application behave as a windows service application on windows. These options are ignored in UNIX-like environment. The documentation will mention this.

Classes and records

`EDaemon`	class	Exception used in all daemon application code.
`TCustomDaemon`	class	Base daemon application class.
`TCustomDaemonApplication`	class	Custom daemon application class.
`TCustomDaemonMapper`	class	Daemon mapper.
`TDaemon`	class	Daemon class for visual development.
`TDaemonApplication`	class	Default descendent of CustomDaemonApplication.
`TDaemonController`	class	Internal daemon controller class.
`TDaemonDef`	class	Daemon definition.
`TDaemonDefs`	class	Collection of daemon definitions.
`TDaemonMapper`	class	Daemon mapper for designing in IDE.
`TDaemonThread`	class	Thread to run daemons in.
`TDependencies`	class	Dependencies collection for a daemon.
`TDependency`	class	Container to define dependencies on other services.
`TWinBindings`	class	Windows Daemon bindings (windows only).

Procedures and functions

`Application`	function	Application instance.
`DaemonError`	procedure	Raise an EDaemon exception.
`RegisterDaemonApplicationClass`	procedure	Register alternative TCustomDaemonApplication class.
`RegisterDaemonClass`	procedure	Register daemon.
`RegisterDaemonMapper`	procedure	Register a daemon mapper class.

Types

`TCurrentStatus`	enumeration	Current daemon status.
`TCustomControlCodeEvent`	procedure type	Prototype for event to handle a custom control code.
`TCustomControlCodeEvEvent`	procedure type
`TCustomDaemonApplicationClass`	type	Class pointer for TCustomDaemonApplication.
`TCustomDaemonClass`	type	Class type for TCustomDaemon.
`TCustomDaemonMapperClass`	type	Class of TCustomDaemonMapper.
`TDaemonClass`	type	Class type of TDaemon.
`TDaemonEvent`	procedure type	Daemon event handler prototype.
`TDaemonOKEvent`	procedure type	Daemon acknowledgement event handler.
`TDaemonOption`	enumeration	Daemon options.
`TDaemonOptions`	set	Set of options.
`TDaemonRunMode`	enumeration	Daemon application run mode.
`TErrorSeverity`	enumeration	Severity of a startup error (Windows only).
`TGuiLoopEvent`	procedure type	GUI loop event mechanism.
`TServiceType`	enumeration	Type of service (Windows only).
`TStartType`	enumeration	When should the daemon be started (windows only).
`TWinControlCode`	enumeration
`TWinControlCodes`	set

Resource strings

`SControlFailed`	resource string	The control code was not handled correctly.
`SCustomCode`	resource string	A custom code was received.
`SDaemonStatus`	resource string	Daemon status report log message.
`SErrApplicationAlreadyCreated`	resource string	A second application instance is created.
`SErrDaemonStartFailed`	resource string	The application failed to start the daemon.
`SErrDuplicateName`	resource string	Duplicate service name.
`SErrNoDaemonDefForStatus`	resource string	Internal error: no daemon definition to report status for.
`SErrNoDaemonForStatus`	resource string	Internal error: no daemon to report status for.
`SErrNoServiceMapper`	resource string	No service mapper was found.
`SErrNothingToDo`	resource string	No operation can be performed.
`SErrOnlyOneMapperAllowed`	resource string	An attempt was made to install a second service mapper.
`SErrServiceManagerStartFailed`	resource string	Unable to start or contact the service manager.
`SErrUnknownDaemonClass`	resource string	Unknown daemon class requested.
`SErrWindowClass`	resource string	Could not register window class.
`SHelpCommand`	resource string	Options message displayed when writing help to the console.
`SHelpInstall`	resource string	Install option message displayed when writing help to the console.
`SHelpRun`	resource string	Run option message displayed when writing help to the console.
`SHelpUnInstall`	resource string	Uninstall option message displayed when writing help to the console.
`SHelpUsage`	resource string	Usage message displayed when writing help to the console.

Variables

`AppClass`	variable	Default class used when creating the application instance.
`CurrentStatusNames`	variable	Names for various service statuses.
`DefaultDaemonOptions`	variable	Default daemon options.
`SStatus`	variable	Status message.

Uses

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.