Re: [wildfly-dev] Discarding the changed management model during operation rollback

Me too > On 1 Jul 2015, at 20:03, Jason Greene <jason.greene(a)redhat.com&gt; wrote: > > I completely agree. > >> On Jul 1, 2015, at 11:43 AM, Brian Stansberry < brian.stansberry(a)redhat.com&gt; wrote: >> >> tl;dr; >> >> When an operation that has changed the management model is rolling back, >> the OperationStepHandlers processing the rollback see the model as it >> was at the arbitrary point when the rollback began. I propose changing >> this so they see things as they were prior to the first change to the model. >> >> Long version: >> >> When an operation mutates either the management Resource tree, or the >> registry of capabilities (together known as the management model), we >> clone the management model and thereafter that operation works on the >> clone. The clone is invisible to other callers until the operations >> successfully commits. When the operation commits, it publishes the clone >> and that becomes the official model. >> >> I call this copy-on-write, publish-on-commit. >> >> If the operation rolls back, the changed model is never published and >> the clone is just discarded when the operation execution returns. >> >> However, while the operation is rolling back, all the >> OperationStepHandlers that are processing the rollback see the modified >> clone, not the original model. They are seeing arbitrarily incorrect data. >> >> This hasn't been a problem up to now, as our standard OSHs get a copy of >> whatever part of the Resource tree they are going to modify and keep it >> for use in rollback. They don't need to re-read the management model to >> perform rollback. >> >> But this doesn't work for the capability registry. If an OSH removes a >> capability and removes a service, and then in rollback tries to use the >> capability to figure out how to restore the service, it fails, as >> management model it can see still shows the capability as being removed. >> >> To fix this, I propose discarding the cloned management model as soon as >> rollback begins. Thereafter, an OSH processing rollback will see the >> model as it was before the first modification. The removed capability >> will still be present. >> >> I have a commit that does this at [1]. Running the testsuite with it >> shows no regressions. This doesn't surprise me, as our standard OSHs up >> to now have had no need to re-read the model during rollback. >> >> [1] >> https://github.com/bstansberry/wildfly-core/commit/419f350931d5b7e345cf9a... >> >> -- >> Brian Stansberry >> Senior Principal Software Engineer >> JBoss by Red Hat >> _______________________________________________ >> wildfly-dev mailing list >> wildfly-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/wildfly-dev > > -- > Jason T. Greene > WildFly Lead / JBoss EAP Platform Architect > JBoss, a division of Red Hat > > > _______________________________________________ > 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