Re: child process in windows services

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Date: Wed, 17 Mar 2004 08:57:40 -0500

Okay, I think I know what you're getting at now. My only suggestion in this
case is to (depending on how you want to make one application dependant on
the other's running state) wait on each other's process handles. For
example, if B.exe launches A.exe, then B.exe can pass it's process handle to
A.exe in the CreateProcess() call, and then A can use a wait function on B's
process handle, and B can use a wait function on A's process handle.

If B notices that A's handle is signalled, then it sets its status to to
SERVICE_STOP_PENDING, and goes through its shutdown routine. If A notices
that B's handle is signalled, it simply terminates.

-- 
John Phillips
MVP - Windows SDK
"Anonuser" <mycorolla02@yahoo.com> wrote in message
news:32946381.0403161602.6cd80227@posting.google.com...
> Thanks John. Here are some more details/questions. Please see below.
>
>
> "John Phillips" <jjphillipsREMOVE@REMOVEhotmail.com> wrote in message
news:<#Jn1j$1CEHA.2052@TK2MSFTNGP11.phx.gbl>...
> > Is A.exe a service by any chance?  If not, just how will it report its
> > status back to the SCM?  Or do you mean that the application is designed
to
> > report its status to its parent or to whomever is interested in A's
status?
> >
>
> A.exe is an executable which is launched via a Service. For eg. the
> Clib book service launches C:\WINNT\system32\clipsrv.exe.
>
> similary "serviceA" launches A.exe . So it is a service.
>
> > If A is a service, then the answer is simple: either make your service
> > dependant on A (so that A will start before your service and if it
fails,
> > then your service will stop), or start A from your service using
> > StartService().  If you start a service via StartService(), then yes,
the
> > newly started service will post its status to the SCM correctly.  It's
not
> > really a matter of who starts the service (your service vs. SCM vs.
anybody
> > else), but if your service application -=behaves=- correctly, by calling
the
> > requisite service registration function on startup, passing a handler
> > function.  Also, the service must be registered via the appropriate
registry
> > entries; statii reporting to the SCM for unregistered services will fall
on
> > deaf ears.
> >
>
> This is a good way but well thats not what I intend to do. I will now
> make "SErviceA" to point to B.exe with some custom settings (like
> setting env. variables) and then within B.exe I want to call (launch)
> A.exe.
>
> Now when I started "ServiceA" from SCM b.exe gets launched followed by
> A.exe.
>
> ServiceA should show as failed even if b.exe or A.exe fails to run.
> If B.exe fails then ServiceA might show as failed even though A.exe is
> still running. So if B.exe fails A.exe should quit/fail and vice
> versa.
>
> I know this is complicated !!!
> Thanks
>
>
>
>
> > What to do to monitor A from B?  Well, that depends on what you want to
do.
> > If A is a service, then you can periodically check its status with
> > QueryServiceStatus().  Otherwise, you can use one of the
WaitForxxxObjects()
> > functions to wait on A's process handle - when A terminates, the handle
> > becomes signalled, and WaitFor...() will succeed.
> >
> >
>
>
>
> "John Phillips" <jjphillipsREMOVE@REMOVEhotmail.com> wrote in message
news:<#Jn1j$1CEHA.2052@TK2MSFTNGP11.phx.gbl>...
> > Is A.exe a service by any chance?  If not, just how will it report its
> > status back to the SCM?  Or do you mean that the application is designed
to
> > report its status to its parent or to whomever is interested in A's
status?
> >
> > If A is a service, then the answer is simple: either make your service
> > dependant on A (so that A will start before your service and if it
fails,
> > then your service will stop), or start A from your service using
> > StartService().  If you start a service via StartService(), then yes,
the
> > newly started service will post its status to the SCM correctly.  It's
not
> > really a matter of who starts the service (your service vs. SCM vs.
anybody
> > else), but if your service application -=behaves=- correctly, by calling
the
> > requisite service registration function on startup, passing a handler
> > function.  Also, the service must be registered via the appropriate
registry
> > entries; statii reporting to the SCM for unregistered services will fall
on
> > deaf ears.
> >
> > What to do to monitor A from B?  Well, that depends on what you want to
do.
> > If A is a service, then you can periodically check its status with
> > QueryServiceStatus().  Otherwise, you can use one of the
WaitForxxxObjects()
> > functions to wait on A's process handle - when A terminates, the handle
> > becomes signalled, and WaitFor...() will succeed.
> >
> >
> > --
> > John Phillips
> > MVP - Windows SDK
> >
> >
> >
> > "Anonuser" <mycorolla02@yahoo.com> wrote in message
> > news:32946381.0403151929.52fa2f97@posting.google.com...
> > > Hi John,
> > > Thanks for the reply. Here is a more detailed description.
> > >
> > > I have a service which launches process A.exe. A.exe is a third party
> > > process to which I dont have access. I want to create a wrapper around
> > > A or an intermediate process called B.exe.
> > >
> > > Not my service launches process B.exe which internally sets some
> > > environment variables and does a create process to launch A.exe.
> > >
> > > A.exe was initially built to report status back to  the Service
> > > control manager.
> > > I have two choices.
> > > So from B.exe if I make a call to SErvice_Main (or equivalent) for
> > > A.exe then A.exe will think that is started by a service and then
> > > report status like STARTED, PENDING. Will these reach the Service
> > > Control Manager since A.exe is the child of process it(SCM) launched.
> > >
> > > OR
> > >
> > > if i directly do a createprocess in B.exe (to create A.exe) to launch
> > > it as an application. What all do I need to do in B.exe to correctly
> > > monitor A's status?
> > >
> > > What will happen if B fails but A is still hanging? What status will
> > > be reported back to SCM(Service control manager)?
> > >
> > > Thanks
> > >
> > >
> > >
> > > "John Phillips" <jjphillipsREMOVE@REMOVEhotmail.com> wrote in message
> >  news:<#xQ8cdpCEHA.3344@tk2msftngp13.phx.gbl>...
> > > > Please see inline...
> > > >
> > > >
> > > > --
> > > > John Phillips
> > > > MVP - Windows SDK
> > > >
> > > >
> > > > "Anonuser" <mycorolla02@yahoo.com> wrote in message
> > > > news:32946381.0403131419.7c20251d@posting.google.com...
> > > > > I have a service which calls into an exec by the name A.exe. Can I
> > > >
> > > > I don't know what you mean by "calls into an exec".  Do you mean
> >  "launches a
> > > > process"?
> > > >
> > > >
> > > > > write a wrapper around A.exe called B.exe which basically does
some
> > > > > custom settings( settng Env variables)  and then call A.exe. So
A.exe
> > > >
> > > > Certainly.  The environment settings of the parent are passed to the
> >  child
> > > > process when calling CreateProcess() and passing NULL for the
> >  lpEnvironment
> > > > parameter.
> > > >
> > > >
> > > > > is the child of B.exe. Would service update messages sent by A.exe
be
> > > > > passed to the Service control manager. What all functions do I
need to
> > > >
> > > > I'm still foggy about which of these things are services (B I assume
is
> > > > not).  But assuming A is launched by a service, then the answer is
no.
> > > > SetServiceStatus() requires a handle to the service which is sending
its
> > > > status, and I'm pretty sure that these handles can't be duplicated
with
> > > > DuplicateHandle().  One way you might accomplish this is for A to
send
> > > > messages to the service (via some IPC method such as COM, Window
> >  Messages,
> > > > Pipes, etc., etc., etc.), and the service would call
SetServiceStatus()
> > > &g
> 8
> t; based
> 68f
>  on the content of the message.
> > > >
> > > >
> > > > > write in the code for B.exe.
> > > >
> > > > You haven't mentioned what B is supposed to do, so this isn't really
a
> >  valid
> > > > question.
> > > >
> > > > >
> > > > > When A.exe dies will the service control manager report the
service as
> > > > > stopped?
> > > >
> > > > No, unless the service tells the SCM that it is stopped.  When A
dies,
> >  it
> > > > can instruct the service to stop, via some IPC mechanism (see
above).
> > > >
> > > >
> > > > > Would I have to monitor A.exe's state in B? I cannot put these
custom
> > > > > settings into A.exe.
> > > >
> > > > Really can't say, seeing as how you're a little short on details.
> > > >
> > > >
> > > > > Thanks

• Previous message: Chandra: "System32 Folder pops up"
• In reply to: Anonuser: "Re: child process in windows services"
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