Re: [wildfly-dev] Design Proposal: Server suspend/resume (AKA Graceful Shutdown)

On Jun 10, 2014, at 10:41 AM, Stuart Douglas <stuart.w.douglas(a)gmail.com&gt; wrote: I don't think so, I think RESTART_REQUIRED means running, but I need to restart to apply management changes (I think that attribute can also be RELOAD_REQUIRED, I think the description may be a bit out of date). To accurately reflect all the possible states you would need something like: RUNNING PAUSING, PAUSED, RESTART_REQUIRED PAUSING_RESTART_REQUIRED PAUSED_RESTART_REQUIRED RELOAD_REQUIRED PAUSING_RELOAD_REQUIRED PAUSED_RELOAD_REQUIRED Which does not seem great, and may introduce compatibility problems for clients that are not expecting these new values. Stuart Dimitris Andreadis wrote: > Isn't RESTART_REQUIRED also orthogonal to RUNNING? > >> On 10/06/2014 17:17, Stuart Douglas wrote: >> They are actually orthogonal, a server can be in both RESTART_REQUIRED >> and any one of the >> suspend states. >> >> RESTART_REQUIRED is very much tied to services and the management >> model, while >> suspend/resume is a runtime only thing that should not touch the state >> of services. >> >> >> Stuart >> >> Dimitris Andreadis wrote: >>> Why not extend the states of the existing 'server-state' attribute to: >>> >>> (STARTING, RUNNING, SUSPENDING, SUSPENDED, RESTART_REQUIRED RUNNING) >>> >>> http://wildscribe.github.io/Wildfly/8.0.0.Final/index.html >>> >>>> On 10/06/2014 04:40, Stuart Douglas wrote: >>>> >>>> Scott Marlow wrote: >>>>>> On 06/09/2014 06:38 PM, Stuart Douglas wrote: >>>>>> Server suspend and resume is a feature that allows a running >>>>>> server to >>>>>> gracefully finish of all running requests. The most common use >>>>>> case for >>>>>> this is graceful shutdown, where you would like a server to >>>>>> complete all >>>>>> running requests, reject any new ones, and then shut down, however >>>>>> there >>>>>> are also plenty of other valid use cases (e.g. suspend the server, >>>>>> modify a data source or some other config, then resume). >>>>>> >>>>>> User View: >>>>>> >>>>>> For the users point of view two new operations will be added to >>>>>> the server: >>>>>> >>>>>> suspend(timeout) >>>>>> resume() >>>>>> >>>>>> A runtime only attribute suspend-state (is this a good name?) will >>>>>> also >>>>>> be added, that can take one of three possible values, RUNNING, >>>>>> SUSPENDING, SUSPENDED. >>>>> The SuspendController "state" might be a shorter attribute name and >>>>> just >>>>> as meaningful. >>>> This will be in the global server namespace (i.e. from the CLI >>>> :read-attribute(name="suspend-state"). >>>> >>>> I think the name 'state' is just two generic, which kind of state >>>> are we >>>> talking about? >>>> >>>>> When are we in the RUNNING state? Is that simply the pre-state for >>>>> SUSPENDING? >>>> 99.99% of the time. Basically servers are always running unless they >>>> are >>>> have been explicitly suspended, and then they go from suspending to >>>> suspended. Note that if resume is called at any time the server goes to >>>> RUNNING again immediately, as when subsystems are notified they should >>>> be able to begin accepting requests again straight away. >>>> >>>> We also have admin only mode, which is a kinda similar concept, so we >>>> need to make sure we document the differences. >>>> >>>>>> A timeout attribute will also be added to the shutdown operation. If >>>>>> this is present then the server will first be suspended, and the >>>>>> server >>>>>> will not shut down until either the suspend is successful or the >>>>>> timeout >>>>>> occurs. If no timeout parameter is passed to the operation then a >>>>>> normal >>>>>> non-graceful shutdown will take place. >>>>> Will non-graceful shutdown wait for non-daemon threads or terminate >>>>> immediately (call System.exit()). >>>> It will execute the same way it does today (all services will shut down >>>> and then the server will exit). >>>> >>>> Stuart >>>> >>>>>> In domain mode these operations will be added to both individual >>>>>> server >>>>>> and a complete server group. >>>>>> >>>>>> Implementation Details >>>>>> >>>>>> Suspend/resume operates on entry points to the server. Any request >>>>>> that >>>>>> is currently running must not be affected by the suspend state, >>>>>> however >>>>>> any new request should be rejected. In general subsystems will >>>>>> track the >>>>>> number of outstanding requests, and when this hits zero they are >>>>>> considered suspended. >>>>>> >>>>>> We will introduce the notion of a global SuspendController, that >>>>>> manages >>>>>> the servers suspend state. All subsystems that wish to do a graceful >>>>>> shutdown register callback handlers with this controller. >>>>>> >>>>>> When the suspend() operation is invoked the controller will invoke >>>>>> all >>>>>> these callbacks, letting the subsystem know that the server is >>>>>> suspend, >>>>>> and providing the subsystem with a SuspendContext object that the >>>>>> subsystem can then use to notify the controller that the suspend is >>>>>> complete. >>>>>> >>>>>> What the subsystem does when it receives a suspend command, and >>>>>> when it >>>>>> considers itself suspended will vary, but in the common case it will >>>>>> immediatly start rejecting external requests (e.g. Undertow will >>>>>> start >>>>>> responding with a 503 to all new requests). The subsystem will also >>>>>> track the number of outstanding requests, and when this hits zero >>>>>> then >>>>>> the subsystem will notify the controller that is has successfully >>>>>> suspended. >>>>>> Some subsystems will obviously want to do other actions on >>>>>> suspend, e.g. >>>>>> clustering will likely want to fail over, mod_cluster will notify the >>>>>> load balancer that the node is no longer available etc. In some >>>>>> cases we >>>>>> may want to make this configurable to an extent (e.g. Undertow >>>>>> could be >>>>>> configured to allow requests with an existing session, and not >>>>>> consider >>>>>> itself timed out until all sessions have either timed out or been >>>>>> invalidated, although this will obviously take a while). >>>>>> >>>>>> If anyone has any feedback let me know. In terms of implementation my >>>>>> basic plan is to get the core functionality and the Undertow >>>>>> implementation into Wildfly, and then work with subsystem authors to >>>>>> implement subsystem specific functionality once the core is in place. >>>>>> >>>>>> Stuart >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> The >>>>>> >>>>>> A timeout attribute will also be added to the shutdown command, >>>>>> _______________________________________________ >>>>>> wildfly-dev mailing list >>>>>> wildfly-dev(a)lists.jboss.org >>>>>> https://lists.jboss.org/mailman/listinfo/wildfly-dev >>>>> _______________________________________________ >>>>> wildfly-dev mailing list >>>>> wildfly-dev(a)lists.jboss.org >>>>> https://lists.jboss.org/mailman/listinfo/wildfly-dev >>>> _______________________________________________ >>>> wildfly-dev mailing list >>>> wildfly-dev(a)lists.jboss.org >>>> https://lists.jboss.org/mailman/listinfo/wildfly-dev >>> _______________________________________________ >>> wildfly-dev mailing list >>> wildfly-dev(a)lists.jboss.org >>> https://lists.jboss.org/mailman/listinfo/wildfly-dev _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev