[jboss-as7-dev] Graceful Shutdown (Revision 2)

[Carlo de Wolf]

It definitely can not be driven by a simple (global) semaphore. If it is 
a fair one, it'll be a throughput bottleneck. If it is an unfair one you 
would get unacceptable round-trip time deviation.

Carlo

On 06/27/2012 01:13 AM, Bill Burke wrote:
> Are you sure explicity granting "permits" through a "Shutdown Manager"
> the way to go?  Having to interact with a central service that grants
> permits per-request is very worrisome.  The subsystem may already have a
> better way to do graceful shutdown, or just cannot follow a permit pattern.
>
> Is it not simpler and gives more flexibility to a subsystem to drive
> this via events rather than explicit callbacks to a Shutdown Manager?
>
> i.e.
>
> class Suspending extends ShutdownEvent
> {
>     void iFinishedSuspending(); // the callback to the Shutdown Manager
> }
>
> GIves the subsystem flexibility on how best to implement a graceful
> shutdown.
>
>
> On 6/26/12 11:00 AM, Jason T. Greene wrote:
>> *EDITED*
>>
>> We've worked out the rough outline of how graceful shutdown will work in
>> AS7.
>>
>> The process of graceful shutdown actually is reflected by a number of
>> states:
>>
>> 1. Running - all services acting normally
>> 2. Suspending - services refuse new "permits" (see below), existing
>> permits are allowed to be retained (and threads running under such a
>> permit may still acquire new permits)
>> 3. Suspended - no permits are present and none may be issued
>> 4. Shutting Down - our existing server stop process / reload admin mode
>>
>> The following transitions are allowed:
>>
>> 1. Running → Suspending: Transition occurs at user request (to suspend
>> or gracefully shut down).
>> 2. Suspending → Suspended: Transition occurs when all permits are cleared.
>> 3. Suspending → Running: Transition occurs at user request (to exit
>> suspend mode or cancel graceful shutdown before it completes).
>> 4. Suspended → Running: Transition occurs at user request (to exit
>> suspend mode).
>> 5. Suspended → Shutting Down: Transition occurs automatically (if a
>> graceful shutdown was requested) or at user request (if a shut down
>> request of any kind is entered in the Suspended state).
>> 6. Running → Shutting Down: Transition occurs at user request (to shut
>> down the server "un-gracefully").
>> 7. Suspending → Shutting Down (User aborts a graceful shutdown)
>>
>> These "permits" are issued by the "Shutdown Manager", whose job is to
>> manage these states.  They are issued corresponding to the following events:
>>
>> 1. The invocation of an EJB method
>> 2. The creation of a web session
>> 3. A creation of a transaction
>> 4. MessageEndpoint and WorkManager aquire permit allowing for release()
>> from a thirdparty to indicate connection close.
>>
>> When a permit cannot be issued due to the server shutting down, a
>> standard exception message should be produced so that the user can see a
>> familiar error message regardless of what mechanism is used to access
>> the server.
>>