I think the main point here is there is no unique way of doing reconciliation and different applications may also have different requirements on this, for example:
- Some application may wipe out all switch data in DS when switch goes down so they can replay everything when switch reconnects. In this case reconciliation is as simple as sending a delete all when switch connects. - Some applications may delete flows but keep groups and meters when switch is down, so they only need to replay flows after switch reconnects. In this case reconciliation just need to synchronize groups/meters when switch connects. - Some applications may react as "nothing happens" when switch goes down so they expect the reconciliation to do all the work of synchronizing flows/groups/meters. Unless we can get a very "smart" reconciliation module that can take care of every possible scenario in an optimal way, I agree we need a framework to let applications do the reconciliation. BR/Luis > On May 10, 2017, at 8:35 AM, Prasanna Huddar <[email protected]> > wrote: > > Hello All, > > If you have any more comments, please share. > > Thanks > Prasanna > > From: Prasanna Huddar > Sent: Friday, March 03, 2017 3:37 PM > To: Anil Vishnoi <[email protected]>; Abhijit Kumbhare > <[email protected]> > Cc: [email protected]; Kanagasundaram K > <[email protected]> > Subject: RE: [openflowplugin-dev] Proposed Reconciliation framework > > Hello Anil, > My inputs inline below > > Thanks, > Prasanna > > From: Anil Vishnoi [mailto:[email protected] > <mailto:[email protected]>] > Sent: 02 March 2017 13:22 > To: Abhijit Kumbhare <[email protected] <mailto:[email protected]>> > Cc: Prasanna Huddar <[email protected] > <mailto:[email protected]>>; > [email protected] > <mailto:[email protected]>; Kanagasundaram K > <[email protected] <mailto:[email protected]>> > Subject: Re: [openflowplugin-dev] Proposed Reconciliation framework > > Hi Prasanna, > > I liked the idea of notifying the applications once the node is reconciled > and ready for further configuration. I have few questions about the proposed > framework in the context of single node + current master-slave implementation: > > (1) I think following is not the case, for sure not for FRM, and i believe > for FRM-Sync as well > Slide-4: > "If Reconciliation fails the ODL disconnects the switch, and the whole > process is repeated by Re-sync and application > Applications start acting on OF switch which is in “unknown” state, which > should be avoided." > > [Prasanna]: Ok, Will reword/ update. If Re-sync fails only options is > reconnect the switch. > > (2) Slide-8: > "Application(s) registering with Reconciliation module is encouraged since: > Applications would know the right Flows and group which needs to be replayed > with write operation(Add / delete / update). > FRM / FRS would not have application view of flows / group, it would blindly > replay the flows / groups. > Also flows having idle / hard timeout can be gracefully handled by > application rather than FRM / FRS." > > Are we assuming the application won't maintain the correct configuration in > the data store ? > [Prasanna]: > No, FRM / FRS would have the right information in data-store, but FRM / > FRS will push all the flows blindly, whereas application can push optimized > set of flows, as covered in couple of points below. > > I believe meter and group always need to be programmed before flow, so is > there any other variance of ordering where we want application to do the > reconciliation ? > [Prasanna]: > Yes, once FRM / FRS or application registers with Reconciliation module, > the algorithm implemented by application can handle all these variances, > algorithm related info are just reccomendations. > > If the flows are installed with idle/hard timeout, we should expect > application to remove it from data store. Unfortunately data store can't help > much here, so application will have to take this burden. > > [Prasanna]: > Agree, but some flow timeouts can happen when Switch is Disconnected from > switch, timeout information is available only in application, using this info > application can re-program the flows as part of re-sync or exclude it. > > So we really keep the clear contract with respect to data store, i don't > really see any reason, why we should leave the node reconciliation to > application. Plugin should do the reconciliation based on the config state in > the data store and once it's done with that reconciliation, it can notify > application to reconcile it's business logic. > > Also in case of controller restart, the only state application will have is > in config data store, and until and unless they run their business logic they > can't figure out the correct ordering. And they can't run the business logic > because there is no node advertized to them yet. > > [Prasanna]: > Regarding Plugin implementing the Reconciliation; > Agree, but plugin should run it as separate bundle, which would be > enabled / disabled through flag. > 1. Since, OVS might support Bundles , but community plugin cannot > accept all other users to use OVS. > a. So, we need to give them option to use their own algorithm(separate > bundle) > b. If future a better algorithm comes up user should be able to move to > it without dependencies. > c. Reconciliation framework infra should work irrespective of > Reconciliation algorithm. > > Regarding node advertisement: > 1. Agree, node is not advertised to application. > 2. But as part of Reconciliation call-back / notification, > reconciliation framework calls the call back function or notification with > switch information. > a. This switch information can be used by application to decide which > flows has to be re-programmed. > i. > Timer is one option to filter out flows. > > (3) If we leave the reconciliation to the applications, and assume that two > applications are using the same node, do we expect that both the application > will have to use the similar kind of reconciliation mechanism? Assuming one > wants to use bundle or one want to use the vanilla reconciliation mechanism > that we have? If not, who will win? If yes, how we will implement it at the > plugin level, because bundle's like features are provided at the plugin > level. So basically i don't see how you can implement different > reconciliation methods without depending on the plugin. I can see that you > can use one method for reconciling specific node, but then all the > application using that node need to use the same method. By doing that we are > basically pushing switch specific reconciliation to the application level, > and in my opinion that's not a good idea. > > [Prasanna]: > We are completely dependent on plugin for all the contracts to > push the flows(meter/flows/groups/etc) down to the switch. > That is why we say Plugin registers with RPC than invokes Reconciliation > framework. > > We do not accept the application to use the same method, but > anything related to algorithm are just recommendation by this framework. > > Scenario; > 1. Consider App1 and App2 have registered to Reconciliation framework. > 2. Plugin gives different contracts to program > flows(flows/group/meter/etc). > a. General flows. > b. Flows with barrier message. > c. Flows using bundles. > 3. App1 and App2 can use any construct of plugin to program the flows. > > We can discuss this more if needed in one of the upcoming calls. > > > (4) slide-9 > > "Check if Reconciliation is needed, if yes, update the DS status of the > Switch and go to Step 6" > > Given that switch is not yet in data store, what really we want to update in > the data store? Also i didn't find the step 6 in the slides. > [Prasanna] > “ Given that switch is not yet in data store, what really we want to update > in the data store? Also i didn't find the step 6 in the slides.” > > Typo will be corrected, no DS reference is needed > > Sorry, Updated the slide just check, no idea with gdrive conversions. > > (5) slide-10 > "9.Application(s) would also wait for error from switch, for pre-defined > time." > > Why do we need to wait for pre-define time?, given that the current API-s do > return the future and future will fail if the configuration on switch fails. > > [Prasanna]: > Ah, than not needed. > > (6) slide -10 > > "10.Application(s) would inform the Reconciliation status to Reconciliation > module." > How long does plugin wait on the application to notify? > > [Prasanna]: > We can make it configurable. > > (7) Proposal says that if any of the application is not able to reconcile > successfully, it should disconnect the device. Assume out of 2 application, > one application is able to reconcile and other one failed, how do > disconnecting the switch will help here ? is there any scenario where we > expect different outcome once switch re-connect? > > [Prasanna]: > > Are you suggesting: > When Reconciliation fails, whether to disconnect or not should be left to > solution? > - Is yes, agree. > > (8) If we push the node reconciliation to applications, are we assuming that > they will use the RPC for flow installation during the reconciliation ? > [Prasanna]: > Yes, we are registering the RPC methods with before invoking the > Reconciliation framework. > But this is not hard requirement, again this is just framework, which should > be flexible for future needs. > > > We can discuss further in one of the calls after Carbon release(or separate > call early, since Carbon is on priority), which is round the corner. > > Thanks > Anil > > On Wed, Feb 22, 2017 at 9:34 AM, Abhijit Kumbhare <[email protected] > <mailto:[email protected]>> wrote: > Just to clarify - this reconciliation workflow as well as bundles based > reconciliation being discussed is for the next release (Nitrogen) and not > part of Carbon. The basic bundles support can be code reviewed & merged as it > is a stretch goal item in the Carbon release plan - however it will not be > used by reconciliation or any other application in Carbon. > > On Wed, Feb 22, 2017 at 4:35 AM, Prasanna Huddar > <[email protected] <mailto:[email protected]>> wrote: > Hello All, > > Please review the proposed new Reconciliation workflow and provide your > inputs. > > Link to the document(1st > draft):https://wiki.opendaylight.org/view/OpenDaylight_OpenFlow_Plugin:Reconciliation#Future_Enhancements > > <https://wiki.opendaylight.org/view/OpenDaylight_OpenFlow_Plugin:Reconciliation#Future_Enhancements> > > Thanks, > Prasanna > > > _______________________________________________ > openflowplugin-dev mailing list > [email protected] > <mailto:[email protected]> > https://lists.opendaylight.org/mailman/listinfo/openflowplugin-dev > <https://lists.opendaylight.org/mailman/listinfo/openflowplugin-dev> > > > _______________________________________________ > openflowplugin-dev mailing list > [email protected] > <mailto:[email protected]> > https://lists.opendaylight.org/mailman/listinfo/openflowplugin-dev > <https://lists.opendaylight.org/mailman/listinfo/openflowplugin-dev> > > > > -- > Thanks > Anil > _______________________________________________ > openflowplugin-dev mailing list > [email protected] > https://lists.opendaylight.org/mailman/listinfo/openflowplugin-dev
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