machi/prototype/tango

Tango prototype TODO list

__ The current checkpoint implementation is fundamentally broken and needs a rewrite, or else. This issue is not mentioned at all in the Tango paper.

option 1: fix checkpoint to be 100% correct option 2: checkpointing is for the weak and the memory-constrained, so don't bother. Instead, rip out the current checkpoint code, period. option 3: other

xx Checkpoint fix option #1: history splicing within the same OID?

xx Checkpoint fix option #2: checkpoint to a new OID, history writes to both OIDs during the CP, then a marker in the old OID to switch over to the new OID?

History splicing has a flaw that I belive just won't work. The switch to a new OID has problems with updates written to the old OID before and before the new checkpoint has finished.

I believe that a checkpoint where: * all Tango writes, checkpoint and non-checkpoint alike, are noted with a checkpoint number. * that checkpoint number is strictly increasing * a new checkpoint has a new checkpoint number * scans ignore blocks with checkpoint numbers larger than the current active checkpoint #, until the checkpoint is complete.

... ought to work correctly.