This is how any type of cache generally works. For example, a Web server proxy cache may serve requests from the cache, if the requested resources are available in the cache, but if a non-existent resource is requested, and the target server is down, the request would return an error to the client for that particular request.
On Fri, Apr 22, 2011 at 7:52 PM, Supun Kamburugamuva <su...@wso2.com> wrote: > On Fri, Apr 22, 2011 at 7:43 PM, Afkham Azeez <az...@wso2.com> wrote: > > Yes, it is consistent. The cache has a cache timeout, and as long as the > > items in the cache are fresh, regardless of the DB being available or > not, > > it is correct to serve from the cache. > > The inconsistency I point out is regarding two resources. If one > resource is available when the db is down and and other is not > available, it is not consistent from the users perspective, specially > when he can't choose to have caching from the registry APIs. If user > explicitly says in his program that caching is required then it is > consistent. But if it happens under the hood without user control > through APIs, it seems in-consistent. > > Thanks, > Supun.. > > > > > On Fri, Apr 22, 2011 at 7:21 PM, Senaka Fernando <sen...@wso2.com> > wrote: > >> > >> Hi Supun, > >> > >> From a Caching PoV, this is consistent. DB-loss can be momentary or > >> pro-longed, but that's not a concern of a cache. And, the prime use-case > of > >> the cache is to make it possible to fetch cached resources instead of > making > >> DB-calls. I see no inconsistency in this model, as Sumedha pointed out > >> earlier. > >> > >> Proper exceptions are thrown when there is a loss of DB connectivity, if > a > >> programmer needs to figure a loss of DB-connectivity (you can check the > >> cause - which is a Throwable; of the exception that's thrown by the > >> registry). But, to me, this is an edge-case, and if there is such a > >> consistency requirement the cache can be disabled. By default, caching > is > >> enabled, and the changes have been made to the registry.xml files found > in > >> carbon core, and files used for testing in carbon components and also at > >> product-level. > >> > >> Thanks, > >> Senaka. > >> > >> On Fri, Apr 22, 2011 at 5:11 PM, Supun Kamburugamuva <su...@wso2.com> > >> wrote: > >>> > >>> Having Caching for fail cases transparently from the user gives an in > >>> consistency. Lets say a user accessed a resource before the registry > >>> database failed. After the registry database has failed, user can > >>> access this particular resource but he may not be able to access > >>> another resource. From a programmers perspective this is not > >>> consistent. > >>> > >>> Thanks, > >>> Supun.. > >>> > >>> On Fri, Apr 22, 2011 at 4:58 PM, Afkham Azeez <az...@wso2.com> wrote: > >>> > > >>> > > >>> > On Fri, Apr 22, 2011 at 4:24 PM, Janaka Ranabahu <jan...@wso2.com> > >>> > wrote: > >>> >> > >>> >> > >>> >> On Fri, Apr 22, 2011 at 3:47 PM, Waruna Ranasinghe <war...@wso2.com > > > >>> >> wrote: > >>> >>> > >>> >>> > >>> >>> On Fri, Apr 22, 2011 at 3:39 PM, Supun Kamburugamuva < > su...@wso2.com> > >>> >>> wrote: > >>> >>>> > >>> >>>> For the users of the registry, it is important to know weather > >>> >>>> registry database is down. > >>> >>>> > >>> >>>> For example we have the requirement of caching the resources at > >>> >>>> theimplemtation > >>> >>>> ESB level and manage these caches according to the ESB specific > >>> >>>> configurations. So I believe we have implemented something that > >>> >>>> should > >>> >>>> have being implemented at the application layer at the registry > >>> >>>> level. > >>> >>>> > >>> >>>> The correct way to implement this kind of functionalities in the > >>> >>>> registry is using an adapter kind of approach. If a user wants > >>> >>>> registry resource caching they can use a adapter to access the > >>> >>>> registry instead of direct access. > >>> >>> > >>> >>> Or we may introduce a mechanism to disable registry caching. In the > >>> >>> current implementation there is no way to disable registry caching. > >>> >> > >>> >> AFAIK Senaka did some changes recently and made registry caching > >>> >> configurable. Also with the default configuration registry caching > is > >>> >> disabled. > >>> > > >>> > default should be caching enabled. > >>> > > >>> >> > >>> >> Thanks, > >>> >> Janaka > >>> >>> > >>> >>> Thanks, > >>> >>> Waruna > >>> >>> > >>> >>>> > >>> >>>> Thanks, > >>> >>>> Supun.. > >>> >>>> > >>> >>>> On Fri, Apr 22, 2011 at 3:29 PM, Sumedha Rubasinghe > >>> >>>> <sume...@wso2.com> > >>> >>>> wrote: > >>> >>>> > How else would you expect a cache to behave? ;-) > >>> >>>> > /sumedha > >>> >>>> > > >>> >>>> > On Fri, Apr 22, 2011 at 3:27 PM, Supun Kamburugamuva > >>> >>>> > <su...@wso2.com> > >>> >>>> > wrote: > >>> >>>> >> > >>> >>>> >> I tried to shut down the registry database and access the > >>> >>>> >> registry > >>> >>>> >> resources. It seems, even though the database is down registry > is > >>> >>>> >> serving the resources from a cache. Is this the behavior of the > >>> >>>> >> registry? > >>> >>>> >> > >>> >>>> >> Thanks, > >>> >>>> >> -- > >>> >>>> >> Supun Kamburugamuva > >>> >>>> >> Technical Lead & Product Manager, WSO2 Inc.; http://wso2.com > >>> >>>> >> Member, Apache Software Foundation; http://www.apache.org > >>> >>>> >> WSO2 Inc.; http://wso2.org > >>> >>>> >> E-mail: su...@wso2.com; Mobile: +94 77 431 3585 > >>> >>>> >> Blog: http://supunk.blogspot.com > >>> >>>> >> _______________________________________________ > >>> >>>> >> Carbon-dev mailing list > >>> >>>> >> Carbon-dev@wso2.org > >>> >>>> >> http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >>> >>>> > > >>> >>>> > > >>> >>>> > _______________________________________________ > >>> >>>> > Carbon-dev mailing list > >>> >>>> > Carbon-dev@wso2.org > >>> >>>> > http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >>> >>>> > > >>> >>>> > > >>> >>>> > >>> >>>> > >>> >>>> > >>> >>>> -- > >>> >>>> Supun Kamburugamuva > >>> >>>> Technical Lead & Product Manager, WSO2 Inc.; http://wso2.com > >>> >>>> Member, Apache Software Foundation; http://www.apache.org > >>> >>>> WSO2 Inc.; http://wso2.org > >>> >>>> E-mail: su...@wso2.com; Mobile: +94 77 431 3585 > >>> >>>> Blog: http://supunk.blogspot.com > >>> >>>> _______________________________________________ > >>> >>>> Carbon-dev mailing list > >>> >>>> Carbon-dev@wso2.org > >>> >>>> http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >>> >>> > >>> >>> > >>> >>> > >>> >>> -- > >>> >>> > >>> >>> > ------------------------------------------------------------------------- > >>> >>> Waruna Ranasinghe > >>> >>> Senior Software Engineer, WSO2 > >>> >>> > >>> >>> Mobile: +94 724 318285 > >>> >>> BLOG: http://warunapw.blogspot.com > >>> >>> > >>> >>> www.wso2.com - "Lean . Enterprise . Middleware" > >>> >>> > >>> >>> _______________________________________________ > >>> >>> Carbon-dev mailing list > >>> >>> Carbon-dev@wso2.org > >>> >>> http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >>> >>> > >>> >> > >>> >> > >>> >> > >>> >> -- > >>> >> Janaka Ranabahu > >>> >> Software Engineer > >>> >> WSO2 Inc. > >>> >> Mobile +94 718370861 > >>> >> Email : jan...@wso2.com > >>> >> Blog : janakaranabahu.blogspot.com > >>> >> > >>> >> _______________________________________________ > >>> >> Carbon-dev mailing list > >>> >> Carbon-dev@wso2.org > >>> >> http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >>> >> > >>> > > >>> > > >>> > > >>> > -- > >>> > Afkham Azeez > >>> > Senior Software Architect & Senior Manager; WSO2, Inc.; > >>> > http://wso2.com, > >>> > > >>> > Member; Apache Software Foundation; http://www.apache.org/ > >>> > email: az...@wso2.com cell: +94 77 3320919 > >>> > blog: http://blog.afkham.org > >>> > twitter: http://twitter.com/afkham_azeez > >>> > linked-in: http://lk.linkedin.com/in/afkhamazeez > >>> > > >>> > Lean . Enterprise . Middleware > >>> > > >>> > _______________________________________________ > >>> > Carbon-dev mailing list > >>> > Carbon-dev@wso2.org > >>> > http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >>> > > >>> > > >>> > >>> > >>> > >>> -- > >>> Supun Kamburugamuva > >>> Technical Lead & Product Manager, WSO2 Inc.; http://wso2.com > >>> Member, Apache Software Foundation; http://www.apache.org > >>> WSO2 Inc.; http://wso2.org > >>> E-mail: su...@wso2.com; Mobile: +94 77 431 3585 > >>> Blog: http://supunk.blogspot.com > >>> _______________________________________________ > >>> Carbon-dev mailing list > >>> Carbon-dev@wso2.org > >>> http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >> > >> > >> > >> -- > >> Senaka Fernando > >> Product Manager - WSO2 Governance Registry; > >> Associate Technical Lead; WSO2, Inc.; http://wso2.com > >> Member; Apache Software Foundation; http://apache.org > >> > >> E-mail: senaka AT wso2.com > >> P: +1 408 754 7388; ext: 51736; M: +94 77 322 1818 > >> Linked-In: http://www.linkedin.com/in/senakafernando > >> > >> Lean . Enterprise . Middleware > >> > >> > >> _______________________________________________ > >> Carbon-dev mailing list > >> Carbon-dev@wso2.org > >> http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > >> > > > > > > > > -- > > Afkham Azeez > > Senior Software Architect & Senior Manager; WSO2, Inc.; http://wso2.com, > > > > Member; Apache Software Foundation; http://www.apache.org/ > > email: az...@wso2.com cell: +94 77 3320919 > > blog: http://blog.afkham.org > > twitter: http://twitter.com/afkham_azeez > > linked-in: http://lk.linkedin.com/in/afkhamazeez > > > > Lean . Enterprise . Middleware > > > > _______________________________________________ > > Carbon-dev mailing list > > Carbon-dev@wso2.org > > http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > > > > > > > > -- > Supun Kamburugamuva > Technical Lead & Product Manager, WSO2 Inc.; http://wso2.com > Member, Apache Software Foundation; http://www.apache.org > WSO2 Inc.; http://wso2.org > E-mail: su...@wso2.com; Mobile: +94 77 431 3585 > Blog: http://supunk.blogspot.com > _______________________________________________ > Carbon-dev mailing list > Carbon-dev@wso2.org > http://mail.wso2.org/cgi-bin/mailman/listinfo/carbon-dev > -- *Afkham Azeez* Senior Software Architect & Senior Manager; WSO2, Inc.; http://wso2.com, * * *Member; Apache Software Foundation; **http://www.apache.org/*<http://www.apache.org/> * email: **az...@wso2.com* <az...@wso2.com>* cell: +94 77 3320919 blog: **http://blog.afkham.org* <http://blog.afkham.org>* twitter: **http://twitter.com/afkham_azeez*<http://twitter.com/afkham_azeez> * linked-in: **http://lk.linkedin.com/in/afkhamazeez* * * *Lean . Enterprise . Middleware*
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