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+The daemonapp unit implements support for daemon (service) applications
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+in free pascal.
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+
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+On Windows, these applications will act as services. On Linux, they are
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+normal command-line applications.
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+
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+The unit implements 3 classes:
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+
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+TDaemonApplication
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+------------------
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+
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+ A TCustomApplication descendent. It is the main entry point for the
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+ application. It handles the starting/stopping/installing of the service.
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+
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+TDaemon
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+-------
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+
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+ A TDatamodule descendent. Here, the actual daemon service code should be
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+ implemented. There are several events:
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+
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+ before/after install
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+ Executed before/after the service is being installed. Mainly useful on
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+ windows. Triggered if the binary is run with the --install option.
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+
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+ before/after uninstall
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+ Executed before/after the service is being installed. Mainly useful on
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+ windows. Triggered if the binary is run with the --uninstall option.
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+
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+ OnStart
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+ Executed when the service is started. This event handler should return
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+ as soon as possible. So at most it should start some event loops or
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+ start a thread which does the actual work. if it takes a long time
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+ to start, call ReportStatus at regular intervals to report the current
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+ status (important on Windows)
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+
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+ OnStop
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+ Executed when the service is stopped. This event handler should return
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+ as soon as possible. if it takes a long time to stop, call ReportStatus
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+ at regular intervals to report the current status (important on Windows)
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+
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+ OnPause
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+ Executed when the service should be paused.
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+
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+ OnContinue
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+ Executed when the service should be continued.
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+
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+ OnShutdown
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+ If stop does not work, the service will be forcedly shut down.
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+
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+The TDaemon class has a property Logger, which is a TEventLog descendent, which
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+can be used to write messages to the system log.
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+
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+An application can contain many daemons/services. Each of them will be run
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+in it's own thread. Only the main program will run in the main thread.
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+
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+TDaemonMapper
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+-------------
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+
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+ This is used to define the service(s) in the system: it contains all
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+ properties with which to define the services in this binary to the system.
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+ The definitions are kept in the DaemonDefs property (a collection)
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+
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+ Each item in the daemondefs collection defines a service: it needs a TDaemon
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+ descendent classname, a name (must be a unique name on the system) a
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+ display name. The winbindings property contains options which are specific to
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+ windows: they correspond to the options one sees in the service manager.
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+
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+ Note that the TDaemonMapper can be used to define 2 services, but they can
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+ use 2 instances of the same TDaemon descendent class to handle the service.
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+
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+ for example: the daemonmapper can be used to create 2 http server daemons,
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+ each which listens on a separate port. TDaemon has a property Definition,
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+ which is the definiton that was used to create the instance.
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+
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+Schematically one could draw it like this:
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+
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+TDaemonApplication
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+ +- TDaemonMapper
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+ +-TDaemonDef1 -> TDaemon instance
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+ +-TDaemonDef2 -> TDaemon instance
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+
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+Note that the daemon instances work independently, they are each running
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+in their own thread. (plus an additional thread which handles the control
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+messages from the windows service manager)
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+
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+There is a lazarus package available which installs support for daemons in
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+the IDE.
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+
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+Michael.
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michael