Hi Mahesh,

What about the other failure situation within BPEL, like
initializeBuildManager and initializeRepositoryManager. Can we do that also
consuming this topics ? Because that also mandatory for the tenant creation
flow. WDYT ?

thanks



*Harsha Thirimanna*
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* <http://www.apache.org/>*
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*Lean . Enterprise . Middleware*


On Wed, Dec 17, 2014 at 1:31 PM, Mahesh Chinthaka <[email protected]> wrote:
>
> Hi all,
>
> Im working on Making the tenants subscription to stratos environments
> fault tolerant [1]
>
> This has been discussed in mail thread with subject  - "[Architecture]
> [AF] Tenant subscribing to stratos environments - making it fault tolerant"
>
> *Issue*
>
> *====*
>
> There are some possible failure points in AF, hence in App Cloud. One such
> critical point is making the tenants subscribed to the dev, test and prod
> stratos environments. Due to any reason, if this step fails, then, thats
> the end of story for that tenant.
>
>
> Actually in appfactory tenant creation,
>
> When a tenant creation request is made, appfactory sends  REST calls to
> stratos environments (dev,prod,test) to create tenants. At the moment there
> is no way to overcome a situation where tenant creation fails in one or
> more stratos environments.
>
> *Proposal*
>
> *=======*
>
> Here what I'm going to do is, integrate WSO2 Message Broker to take tenant
> creation requests to a durable topic and manipulate the process in a
> fault tolerant manner. The durable topic will keep messages around
> persistently for any suitable consumer to consume them.
>
>
> Appfactory will have a publisher who publishes messages in the topic
> inside MB when a tenant creation is requested.
>
>
> There will be a subscriber for each stratos environment who is listening
> to above topic(create_teanant). If subscription is successfull then
> subscriber will acknowledge to MB and MB will not send that particular
> request to same subscriber again. If subscription got failed subscriber
> will not ack. and MB will take care of sending that request until it
> becomes successful.
>
>
> At the moment we have 3 stratos environments therefore we will have 3
> subscribers listening to that particular topic(create_teanant) in MB. In a
> case of AF having more stratos environments in future, it is possible to
> add more subscribers. Durable topic subscribers[2] will be used here since
> it will persist the subscription on behalf of the client subscription when
> client is not online.
>
>
> This step is not synchronous therefore  above changes will not effect the
> tenant creation flow.
>
>
> *Architectural diagram *
>
> *=================*
>
> Architectural diagram can be found in [3]
>
>
>
> ​
>
>
> [1] - https://wso2.org/jira/browse/APPFAC-2436
>
> [2] -
> https://docs.wso2.com/display/MB220/Creating+a+Durable+Topic+Subscription
>
> [3] -
> https://docs.google.com/a/wso2.com/drawings/d/15CmM3rCTwjUUu4V6lp2WX32nRzufraDXawALNYIoTek/edit
>
> --
> *Mahesh Chinthaka Vidanagama* | Software Engineer
> WSO2, Inc | lean. enterprise. middleware.
> #20, Palm Grove, Colombo 03, Sri Lanka
> Mobile: +94 71 63 63 083 | Work: +94 112 145 345
> Email: [email protected] | Web: www.wso2.com
>
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>
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