cshannon opened a new pull request, #5187:
URL: https://github.com/apache/accumulo/pull/5187
This adds a new Mergeability column for marking if/when tablets are eligible
to me merged by the system based on a threshold. The column stores a duration
that is relative to the time the Manager uses, Steady time.
There are 3 possible states for the value:
1) -1 : This means a tablet will never automatically merge
2) 0 : Tablet is eligible now to automatically merge
3) positive duration: eligible to merge after the given duration relative
to the current system Steady time. Ie. the tablet can be merged if
SteadyTime is later than the given duration.
This change only adds the new column itself and populates it. The default is
to never merge automatically for all cases except for when the system
automatically splits tablets. In that case the newly split tablets are marked
as being eligible to merge immediately.
Future updates will add API enhancements to allow setting/viewing the
mergeability setting as well as to enable automatic merging by the system that
is based on this new column value.
When automatic merging is enabled, if a user wants to make a tablet elgible
to be merged in the future they would do so by adding a period of time to the
current SteadyTime. For example, to make a tablet eligible to be merged 3 days
from now the user would read the current SteadyTime value (represented as a
duration), add 3 days to that and then store that new duration in the column.
When the current steady time passes that duration the tablet would be eligible
to be merged.
See #5014 for more details
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