Xbase++

Cancel HTTP Get Async Task if not Completed after a Max Time

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Demonstrates how to wait a maximum amount of time for an asynchronous task to completed. If not completed in the allotted amount of time, the task is cancelled. Xbase++

LOCAL nSuccess
LOCAL oHttp
LOCAL cUrl
LOCAL oTask
LOCAL nWaitMaxMs
LOCAL nWasCanceled
LOCAL cResponseStr

nSuccess := 0

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

oHttp := CreateObject("Chilkat.Http")

//  Set some timeouts, in seconds:
oHttp:ConnectTimeout := 15
//  ReadTimeout specifies the max number of seconds that must elapse when no additional data is received before
//  timing out.  For example, if a server sends a 300 byte response at the rate of 1 byte per second, then
//  ReadTimeout would never cause a timeout because there is never a 15 second interval when nothing arrives.
oHttp:ReadTimeout := 15

cUrl := "https://your-url.com/something"
oTask := oHttp:QuickGetStrAsync(cUrl)
oTask:Run()

//  Wait a maximum of waitMaxMs for the task (i.e. the HTTP GET) to complete.
//  The Wait method returns when the task has been canceled, aborted, or completed, or when the max allotted time has passed.
nWaitMaxMs := 20000
oTask:Wait(nWaitMaxMs)

//  At this point, the GET may or may not have completed.  
//  Rather than checking the Task status, we can call task.Cancel because
//  if the Task is no longer running (because it already completed, was canceled or aborted), then the 
//  call to Cancel is a NO-OP (meaning it does nothing and the Task's status is unaffected).
//  Also, task.Cancel returns 1 if the task was in the "queued" or "running" state and was canceled or aborted. 
//  The method returns 0 if the task has any other status.
nWasCanceled := oTask:Cancel()
IF (nWasCanceled == 1)
    ? "The HTTP GET took too long and was canceled."
ELSE
    //  Find out what happened.
    IF (oTask:StatusInt == 7)
        //  The task completed, which means the background thread's call to QuickGetStr completed
        //  with success or failure.  Find out which...
        IF (oTask:TaskSuccess == 1)
            //  Get the string response for the call to QuickGetStr (which happened in Chilkat's background thread).
            cResponseStr := oTask:GetResultString()
            ? cResponseStr
            ? "HTTP GET successful!"
        ELSE
            ? "HTTP GET failed prior to waitMaxMs..."
            ? oTask:ResultErrorText
        ENDIF

    ELSE
        //  The task must've been canceled or aborted by some other means..
        ? "Task did not complete.  Final status: " + oTask:Status
    ENDIF

ENDIF

oTask:destroy()

oHttp:destroy()