[jira] [Updated] (MESOS-6090) Change master to always update registry before in-memory state

["Neil Conway (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MESOS-6090?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Neil Conway updated MESOS-6090:
-------------------------------
    Description: 
When a new slave attempts to register, the registry is updated first, then the master's in-memory state is updated if the registry operation is applied successfully. However, when a slave is removed or marked unreachable, the master first updates its in-memory state, then updates the registry. This has two problems:

1. It makes it harder to reason about the correctness of concurrent operations that read in-memory state and update the registry.
2. It can leak incorrect information via the HTTP endpoints. That is, if we update the master's in-memory state on removal or marking a slave unreachable, that change will be observable via the HTTP endpoints. If the master then fails over (and the registry operation fails), the information returned via the endpoint will be incorrect. The master has special code to avoid this inaccuracy for reconciliation (see {{Master::transitioning()}}), but not for the endpoints.

I think it is simpler to just always update the registry first.

  was:
When a new slave attempts to register, the registry is updated first, then the master's in-memory state is updated if the registry operation is applied successfully. However, when a slave is removed or reregisters, the master first updates its in-memory state, then updates the registry. This has two problems:

1. It makes it harder to reason about the correctness of concurrent operations that read in-memory state and update the registry.
2. It can leak incorrect information via the HTTP endpoints. That is, if we update the master's in-memory state on removal or reregistration, that change will be observable via the HTTP endpoints. If the master then fails over (and the registry operation fails), the information returned via the endpoint will be incorrect. The master has special code to avoid this inaccuracy for reconciliation (see {{Master::transitioning()}}), but not for the endpoints.

I think it is simpler to just always update the registry first.


> Change master to always update registry before in-memory state
> --------------------------------------------------------------
>
>                 Key: MESOS-6090
>                 URL: https://issues.apache.org/jira/browse/MESOS-6090
>             Project: Mesos
>          Issue Type: Improvement
>          Components: master
>            Reporter: Neil Conway
>            Assignee: Neil Conway
>              Labels: mesosphere
>
> When a new slave attempts to register, the registry is updated first, then the master's in-memory state is updated if the registry operation is applied successfully. However, when a slave is removed or marked unreachable, the master first updates its in-memory state, then updates the registry. This has two problems:
> 1. It makes it harder to reason about the correctness of concurrent operations that read in-memory state and update the registry.
> 2. It can leak incorrect information via the HTTP endpoints. That is, if we update the master's in-memory state on removal or marking a slave unreachable, that change will be observable via the HTTP endpoints. If the master then fails over (and the registry operation fails), the information returned via the endpoint will be incorrect. The master has special code to avoid this inaccuracy for reconciliation (see {{Master::transitioning()}}), but not for the endpoints.
> I think it is simpler to just always update the registry first.



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