delphi - terminate all the threads (TThread) on closing application - delphi

Question

My application is a tcp/ip server, with main thread created only once & listening all the time. When new client connects, the main thread creates the new thread of TClientThread type. There is however no list of running Client threads, as that would make my app a bit complicated... is there any way to execute "terminate" method on all the threads, even if the thread is busy (in my case "busy" means it's waiting for the data, where the timeout set is about 30 sec ... so I have to kill it anyway, without waiting.)?
The simple closing application seems not to run "terminate" method on the threads, which ends up with memory leaks reported by FastMM...

Answer 1

Memory leaks on shutdown are nothing to worry about - going to the trouble of freeing memory before returning control to the operating system is a waste of time and needlessly slows down application exit. All you really need to do is ensure that all data has been saved, and all interprocess handles (such as semaphores and mutexes) correctly released, and exit away.
For notifying clients, the best you can do would be a strategy somewhat like this:
Add all client-handling threads to some list somewhere (with suitable locking on creation, destruction and iteration)
Make client threads remove themselves from the list upon termination, and have the last item removed from the list set an event (manual reset event, e.g. TEvent in SyncObjs) if the server is shutting down
Introduce polling (e.g. select or equivalent with a timeout) or other kind of interruption (e.g. SO_RCVTIMEO / SO_SNDTIMEO) in what would otherwise be long-running blocking routines, monitoring the Terminated property
On shutdown, lock the list and iterate through it, calling Terminate, and then wait for the event to be signaled; of course, the listening socket which adds items to the list should be closed and known to be closed before iterating through the list

Answer 2

Sounds like this article may help
What you'll see if you click that link:
Using Semaphores in Delphi, Part 2:
The Connection Pool
By: Cary Jensen
Abstract: Semaphores are used to
coordinate multiple threads and
processes. That semaphores provide
multiple threads with simultaneous
access to a shared resource is
highlighted by the
TFixedConnectionPool class described
in this article.

Answer 3

I use a KillThreadList: TList global.
I monitor it in my thread as:
while (Not Terminated) do
begin
inc(Inker);
if (WaitForSingleObject(FTick, finterval) = WAIT_TIMEOUT) then
Begin
if Inker >= 10 then
Begin
ProcessTables;
Inker := 0;
sleep(1000);
End;
if KillThreadList.Contains(ThreadID) = True then Terminate;
End;
end;
I also test for the KillThreadList in my processes to let me opt out of them before completion, where safe to do so.
I pass the OnTerminate event out to the Main thread and remove the ThreadID from the KillList there. I use this model extensively and it has not failed me yet.
procedure TfrmProcessQualcommLocations.OnTerminateThread;
var
ThreadID : Cardinal;
i : integer;
aStatusBar :TStatFrame;
begin
ThreadID := (Sender as Tthread).ThreadID;
for i := 0 to StatusBarList.Count -1 do
Begin
if StatusBarList.Items[i].ThreadID = ThreadID then
Begin
aStatusBar := StatusBarList.Items[i];
KillThreadList.Extract(ThreadID);
StatusBarList.Extract(aStatusBar);
aStatusBar.Free;
break;
End;
End;
self.Refresh;
end;
In the case above, I am also removing some GUI stuff.
Hope that helps.
SpringerRider