Neil Conway created MESOS-6090:
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Summary: 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
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.
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