ServiceWait (Function)

ONLINE HELP
WINDEV, WEBDEV AND WINDEV MOBILE

Version:

Home | Sign in | English

Tips
Use mode

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

ServiceWait (Function)

In french: ServiceTemporise

Pauses the current service during the specified duration.

Remark: This function is ignored if it is not called in a Service application.

Example

// -- Running the service (called in loop) --

// Main loop of the service
// Check the presence of files in the directory
sFileList is string
sFileList = fListFile("c:\temp\entry\*.*", frNotRecursive)

// If files have been included in the directory, they are processed by the service
IF sFileList <> "" THEN
ProcessFileList(sFileList)
END

// Wait during 10 seconds between two loops
ServiceWait(10*100)

Syntax

ServiceWait(<Wait>)

<Wait>: Integer ou Duration

Timeout defined for the current thread of service (in hundredths of a second). This parameter can correspond to:
an integer corresponding to the number of hundredths of a second,
a Duration variable,
the duration in a readable format (e.g., 1 s or 10 ms).

Remarks

Tips

A Service application runs the "Service execution" event in a loop. To avoid consuming the computer's processor resources, ServiceWait must be used at the end of this event.
Multitask, Wait or ThreadPause must not be used in a Service application.

Use mode

ServiceWait is required if the service code does not perform the timeout by itself.
The execution of ServiceWait is automatically ended if a request for stopping the service occurs.

Let's see a classification of types of services and the use cases of ServiceWait.

Category 1
When ServiceWait is useless: when the service waits for an external request. For example:
- a server for communicating by sockets that waits for a connection request (SocketWaitForConnection)
- a service that waits for an external signal (EventWait)
- a service waiting for an internal synchronization of threads.
In these cases, ServiceWait has no effect. However, a specific stop code must be used to interrupt the wait.
Remark: A standard service proposes services to the other processes: therefore, it is waiting for external "commands" and is in category 1 for which ServiceWait has no effect.
Category 2
When ServiceWait is not very useful: checks in quick loops (one second). For example, checking the status of a database file one a regular basis.
The service stays for less than one second in the timeout and ThreadPause is sufficient. In a stop is requested, this stop will be performed at the end of the loop, therefore after a wait of a few seconds.
Category 3
When ServiceWait is very useful: checks spaced out in time. For example, processing a spool of files in a directory with directory checks every 5 minutes.
Remark: In this case, a schedule task is recommended.

Component: wd270vm.dll