Zinc: Are start and stop meant to be idempotent?
Locked
Zinc: Are start and stop meant to be idempotent?
 
|
Hi,
Looking at ZnServer >> start and ZnSingleThreadedServer >> stop (as ZnServer >> stop is #subclassResponsibility), I had the impression they are meant to be idempotent. The start comment is: "Start me. I will start listening on my port for incoming HTTP connections. If I am running, I will first stop and thus effectively restart" The stop comment is: "Stop me. I will stop listening on my port for incoming HTTP connections. Does nothing when I am not running" So, it seems like both start and stop try to be safe to be sent twice in a row. I did a few Transcript prints: --- 1. just stop: is ok. ZnManagingMultiThreadedServer allInstances do: #stop. ZnServer managedServers do: #unregister. Smalltalk garbageCollect. (ZnServer on: 4998) stop. (ZnServer on: 4997) stop; stop. Transcript show: ZnServer managedServers; cr; show: ZnManagingMultiThreadedServer allInstances; cr. ==> an IdentitySet() an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) --- 2. start; stop: is ok. ZnManagingMultiThreadedServer allInstances do: #stop. ZnServer managedServers do: #unregister. Smalltalk garbageCollect. (ZnServer on: 4998) start; stop. (ZnServer on: 4997) start; stop; stop. Transcript show: ZnServer managedServers; cr; show: ZnManagingMultiThreadedServer allInstances; cr. ==> an IdentitySet() an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) --- 3. register; start; stop: is ok. ZnManagingMultiThreadedServer allInstances do: #stop. ZnServer managedServers do: #unregister. Smalltalk garbageCollect. (ZnServer on: 4998) register; start; stop. (ZnServer on: 4997) register; start; stop; stop. Transcript show: ZnServer managedServers; cr; show: ZnManagingMultiThreadedServer allInstances; cr. ==> an IdentitySet() an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) --- 4. start: is ok. ZnManagingMultiThreadedServer allInstances do: #stop. ZnServer managedServers do: #unregister. Smalltalk garbageCollect. (ZnServer on: 4998) start. (ZnServer on: 4997) start; start. Transcript show: ZnServer managedServers; cr; show: ZnManagingMultiThreadedServer allInstances; cr. ==> an IdentitySet() an Array(a ZnManagingMultiThreadedServer(running 4998) a ZnManagingMultiThreadedServer(running 4997)) 5. register; start: is not ok. ZnManagingMultiThreadedServer allInstances do: #stop. ZnServer managedServers do: #unregister. Smalltalk garbageCollect. (ZnServer on: 4998) register; start. (ZnServer on: 4997) register; start; start. Transcript show: ZnServer managedServers; cr; show: ZnManagingMultiThreadedServer allInstances; cr. ==> an IdentitySet(a ZnManagingMultiThreadedServer(running 4998)) an Array(a ZnManagingMultiThreadedServer(running 4998) a ZnManagingMultiThreadedServer(running 4997)) The last case is not idempotent for #start. With one #start, the server is registered, with two #start's, it is not registered. Shouldn't the last case be idempotent as well? If it is, it is the bug that should be put into issue tracker? Herby |
Re: Zinc: Are start and stop meant to be idempotent?
|
|
Herby,
In Zn #bleedingEdge === Name: Zinc-HTTP-SvenVanCaekenberghe.464 Author: SvenVanCaekenberghe Time: 27 July 2017, 1:10:32.048978 pm UUID: 63589259-ac11-0d00-9153-678c0082c0ce Ancestors: Zinc-HTTP-SvenVanCaekenberghe.460 Make ZnSingleThreadedServer>>#start idempotent (since it called #stop and #stop does a #unregister there was a possible side effect, call #stop: false from #start instead) [thx Herby Vojčík] === This still does not solve the core problem of #startUp[:] being called twice (apparently) in some situation. But some extra protection won't hurt. Thx for the suggestion, I hope this solves your current issue (remember to load Zn #bleedingEdge). Sven > On 26 Jul 2017, at 20:19, Herby Vojčík <[hidden email]> wrote: > > Hi, > > Looking at ZnServer >> start and ZnSingleThreadedServer >> stop (as ZnServer >> stop is #subclassResponsibility), I had the impression they are meant to be idempotent. > > The start comment is: > > "Start me. I will start listening on my port for incoming HTTP connections. > If I am running, I will first stop and thus effectively restart" > > The stop comment is: > > "Stop me. I will stop listening on my port for incoming HTTP connections. > Does nothing when I am not running" > > So, it seems like both start and stop try to be safe to be sent twice in a row. > > I did a few Transcript prints: > > --- > > 1. just stop: is ok. > > ZnManagingMultiThreadedServer allInstances do: #stop. > ZnServer managedServers do: #unregister. > Smalltalk garbageCollect. > > (ZnServer on: 4998) stop. > (ZnServer on: 4997) stop; stop. > > Transcript show: ZnServer managedServers; cr; > show: ZnManagingMultiThreadedServer allInstances; cr. > > ==> > > an IdentitySet() > an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) > > --- > > 2. start; stop: is ok. > > ZnManagingMultiThreadedServer allInstances do: #stop. > ZnServer managedServers do: #unregister. > Smalltalk garbageCollect. > > (ZnServer on: 4998) start; stop. > (ZnServer on: 4997) start; stop; stop. > > Transcript show: ZnServer managedServers; cr; > show: ZnManagingMultiThreadedServer allInstances; cr. > > ==> > > an IdentitySet() > an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) > > --- > > 3. register; start; stop: is ok. > > ZnManagingMultiThreadedServer allInstances do: #stop. > ZnServer managedServers do: #unregister. > Smalltalk garbageCollect. > > (ZnServer on: 4998) register; start; stop. > (ZnServer on: 4997) register; start; stop; stop. > > Transcript show: ZnServer managedServers; cr; > show: ZnManagingMultiThreadedServer allInstances; cr. > > ==> > > an IdentitySet() > an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) > > --- > > 4. start: is ok. > > ZnManagingMultiThreadedServer allInstances do: #stop. > ZnServer managedServers do: #unregister. > Smalltalk garbageCollect. > > (ZnServer on: 4998) start. > (ZnServer on: 4997) start; start. > > Transcript show: ZnServer managedServers; cr; > show: ZnManagingMultiThreadedServer allInstances; cr. > > ==> > > an IdentitySet() > an Array(a ZnManagingMultiThreadedServer(running 4998) a ZnManagingMultiThreadedServer(running 4997)) > > 5. register; start: is not ok. > > ZnManagingMultiThreadedServer allInstances do: #stop. > ZnServer managedServers do: #unregister. > Smalltalk garbageCollect. > > (ZnServer on: 4998) register; start. > (ZnServer on: 4997) register; start; start. > > Transcript show: ZnServer managedServers; cr; > show: ZnManagingMultiThreadedServer allInstances; cr. > > ==> > > an IdentitySet(a ZnManagingMultiThreadedServer(running 4998)) > an Array(a ZnManagingMultiThreadedServer(running 4998) a ZnManagingMultiThreadedServer(running 4997)) > > The last case is not idempotent for #start. With one #start, the server is registered, with two #start's, it is not registered. > > Shouldn't the last case be idempotent as well? > > If it is, it is the bug that should be put into issue tracker? > > Herby > |
Re: Zinc: Are start and stop meant to be idempotent?
|
|
Sven Van Caekenberghe wrote:
> Herby, > > In Zn #bleedingEdge > > === > Name: Zinc-HTTP-SvenVanCaekenberghe.464 > Author: SvenVanCaekenberghe > Time: 27 July 2017, 1:10:32.048978 pm > UUID: 63589259-ac11-0d00-9153-678c0082c0ce > Ancestors: Zinc-HTTP-SvenVanCaekenberghe.460 > > Make ZnSingleThreadedServer>>#start idempotent (since it called #stop and #stop does a #unregister there was a possible side effect, call #stop: false from #start instead) [thx Herby Vojčík] > === > > This still does not solve the core problem of #startUp[:] being called twice (apparently) in some situation. But some extra protection won't hurt. Yes, it will solve it, but mask the bigger problem. OTOH, adding debug output to #start can uncover it for those who want to experiment. Thanks, Herby P.S.: I'll wait with it until I need it, maybe it gets blessed before it it a real problem (on the dev machine, I can have no --headless for a while). > Thx for the suggestion, I hope this solves your curren t issue (remember to load Zn #bleedingEdge). > > Sven > >> On 26 Jul 2017, at 20:19, Herby Vojčík<[hidden email]> wrote: >> >> Hi, >> >> Looking at ZnServer>> start and ZnSingleThreadedServer>> stop (as ZnServer>> stop is #subclassResponsibility), I had the impression they are meant to be idempotent. >> >> The start comment is: >> >> "Start me. I will start listening on my port for incoming HTTP connections. >> If I am running, I will first stop and thus effectively restart" >> >> The stop comment is: >> >> "Stop me. I will stop listening on my port for incoming HTTP connections. >> Does nothing when I am not running" >> >> So, it seems like both start and stop try to be safe to be sent twice in a row. >> >> I did a few Transcript prints: >> >> --- >> >> 1. just stop: is ok. >> >> ZnManagingMultiThreadedServer allInstances do: #stop. >> ZnServer managedServers do: #unregister. >> Smalltalk garbageCollect. >> >> (ZnServer on: 4998) stop. >> (ZnServer on: 4997) stop >> >> Transcript show: ZnServer managedServers; cr; >> show: ZnManagingMultiThreadedServer allInstances; cr. >> >> ==> >> >> an IdentitySet() >> an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) >> >> --- >> >> 2. start; stop: is ok. >> >> ZnManagingMultiThreadedServer allInstances do: #stop. >> ZnServer managedServers do: #unregister. >> Smalltalk garbageCollect. >> >> (ZnServer on: 4998) start; stop. >> (ZnServer on: 4997) start; stop; stop. >> >> Transcript show: ZnServer managedServers; cr; >> show: ZnManagingMultiThreadedServer allInstances; cr. >> >> ==> >> >> an IdentitySet() >> an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) >> >> --- >> >> 3. register; start; stop: is ok. >> >> ZnManagingMultiThreadedServer allInstances do: #stop. >> ZnServer managedServers do: #unregister. >> Smalltalk garbageCollect. >> >> (ZnServer on: 4998) register; start; stop. >> >> >> Transcript show: ZnServer managedServers; cr; >> show: ZnManagingMultiThreadedServer allInstances; cr. >> >> ==> >> >> an IdentitySet() >> an Array(a ZnManagingMultiThreadedServer(stopped 4998) a ZnManagingMultiThreadedServer(stopped 4997)) >> >> --- >> >> 4. start: is ok. >> >> ZnManagingMultiThreadedServer allInstances do: #stop. >> ZnServer managedServers do: #unregister. >> Smalltalk garbageCollect. >> >> (ZnServer on: 4998) start. >> (ZnServer on: 4997) start; start. >> >> Transcript show: ZnServer managedServers; cr; >> show: ZnManagingMultiThreadedServer allInstances; cr. >> >> ==> >> >> an IdentitySet() >> an Array(a ZnManagingMultiThreadedServer(running 4998) a ZnManagingMultiThreadedServer(running 4997)) >> >> 5. register; start: is not ok. >> >> ZnManagingMultiThreadedServer allInstances do: #stop. >> ZnServer managedServers do: #unregister. >> Smalltalk garbageCollect. >> >> (ZnServer on: 4998) register; st >> (ZnServer on: 4997) register; start; start. >> >> Transcript show: ZnServer managedServers; cr; >> show: ZnManagingMultiThreadedServer allInstances; cr. >> >> ==> >> >> an IdentitySet(a ZnManagingMultiThreadedServer(running 4998)) >> an Array(a ZnManagingMultiThreadedServer(running 4998) a ZnManagingMultiThreadedServer(running 4997)) >> >> The last case is not idempotent for #start. With one #start, the server is registered, with two #start's, it is not registered. >> >> Shouldn't the last case be idempotent as well? >> >> If it is, it is the bug that should be put into issue tracker? >> >> Herby >> > > |
«
Return to Pharo Smalltalk Users
|
1 view|%1 views
| Free forum by Nabble | Edit this page |