[SERVER-61033] Remove permitMigrations flag and implementation Created: 27/Oct/21  Updated: 26/Oct/23

Status: Backlog
Project: Core Server
Component/s: Sharding
Affects Version/s: None
Fix Version/s: None

Type: Task Priority: Major - P3
Reporter: Marcos José Grillo Ramirez Assignee: Backlog - Catalog and Routing
Resolution: Unresolved Votes: 0
Labels: oldshardingemea
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Assigned Teams:
Catalog and Routing
Participants:

 Description   

SERVER-56226 introduced the permitMigrations flag for versions older than 5.0, however, this flag is only a workaround until PM-2423 and PM-1631 are finished. Once those projects are completed, we can safely remove the permitMigrations flag and the setAllowMigrations user face command.



 Comments   
Comment by Marcos José Grillo Ramirez [ 14/Dec/21 ]

We need to wait until both depended projects are finished before implementing these changes.

Comment by Marcos José Grillo Ramirez [ 02/Dec/21 ]

As kaloian.manassiev said, I meant PM-1631, sorry for the confusion. PM-2423 would also prevent surprises from a user perspective. garaudy.etienne yes, we can keep the flags until the projects are finished.

Comment by Kaloian Manassiev [ 02/Dec/21 ]

marcos.grillo, I think you meant PM-1631, not PM-2423. Like you correctly pointed out to me in our Zoom call yesterday, the customer's problem is not the writes to orphaned documents, but the fact that some documents may not get updated due to ongoing chunk migrations.

As a consequence, I think we need to keep both flags until both PM-1631 and PM-2423 are done.

Comment by Garaudy Etienne [ 01/Dec/21 ]

Let me double-check that there isn't another user case missing. For now, can we keep the flags and remove them in 6.0?

Comment by Marcos José Grillo Ramirez [ 01/Dec/21 ]

After talking with kaloian.manassiev we realized something about the setAllowMigrations command. From a user perspective, we have 2 scenarios:

  • The user wants to stop the balancer because it has some custom code that balances the cluster
  • The user doesn't want multi writes on orphaned documents, so it needs to stop migrations

The first scenario is already covered by enableBalancer, and the setAllowMigrations is currently a workaround for the second, however, after the work of PM-2423 is finished, the second scenario simply won't occur. So, this ticket could be simply removing the permitMigrations flag and the setAllowMigrations command altogether.

garaudy.etienne does this sound reasonable? do you think there is a user case we're missing?

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