PowerBuilder

Monitor and Cancel a Running DKIM Operation

Demonstrates the Chilkat Dkim.HeartbeatMs and Dkim.AbortCurrent properties, which monitor and cancel a long-running operation such as a DNS public-key lookup. HeartbeatMs sets how often an AbortCheck event fires, and AbortCurrent requests cancellation.

Background: Most Dkim work is instant, but anything touching DNS can stall on a slow or unresponsive server. HeartbeatMs makes the object emit a periodic AbortCheck callback during such calls so an application stays responsive and can show progress, and AbortCurrent — set from that callback or from another thread — breaks a blocked synchronous call out early. Together they turn an otherwise uninterruptible operation into a cancellable one.

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PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Dkim

li_Success = 0

//  Demonstrates the Dkim properties HeartbeatMs and AbortCurrent, which monitor and cancel a
//  long-running operation such as a DNS public-key lookup.

loo_Dkim = create oleobject
li_rc = loo_Dkim.ConnectToNewObject("Chilkat.Dkim")
if li_rc < 0 then
    destroy loo_Dkim
    MessageBox("Error","Connecting to COM object failed")
    return
end if

//  Fire an AbortCheck event callback every 100 ms during method calls.  In programming languages
//  where Chilkat supports event callbacks, the callback can request cancellation.
loo_Dkim.HeartbeatMs = 100

//  AbortCurrent may be set to 1 to request cancellation of a running operation.  It is
//  typically set from another thread, or from within an AbortCheck callback.  Setting it 0
//  here ensures the operation is not pre-emptively aborted.
loo_Dkim.AbortCurrent = 0

//  PrefetchPublicKey performs a synchronous DNS lookup, which HeartbeatMs monitors and
//  AbortCurrent can cancel.
li_Success = loo_Dkim.PrefetchPublicKey("myselector","example.com")
if li_Success = 0 then
    Write-Debug loo_Dkim.LastErrorText
    destroy loo_Dkim
    return
end if

Write-Debug "Public key prefetched."


destroy loo_Dkim