We decided at the 6 week review that the donor should bound how long it blocks operations.
This is useful in general to limit the impact of a tenant migration on a user workload, but in particular is useful in case the donor starts blocking very soon after writing a commitIndexBuild oplog entry. This is because the recipient will not start building the index until seeing commitIndexBuild in the oplog; will not report that it has majority-committed the commitIndexBuild oplog entry until finishing building the index; and building the index can take a long time (hours).
evin.roesle, could you propose a default upper bound for how long the donor should block operations? The upper bound should be settable via a server parameter.