Opportunistic replication

[RubenKelevra]

Describe the feature you are proposing

When you run a collaborative cluster, you may not know how many nodes there are at any given time. But you like to add a min/max replication value, to not spread all pins to all nodes - if there are many.

Say I want to save 2 TB of 200 pins. If there are 500 nodes it would be nice to have just 10-15 copies of every pin.

So each node just have to save a fraction of the whole pinset.

But when I start out, I don't run 10 nodes. This means I can't set it to 10-15 but need to set it to 1-15. But this means, the pins may get lost, as the cluster will only act on not having the minimum redundancies.

The solution would be, to set the replication level to opportunistic 10-15. So the cluster would put up to 15 members into the allocation list, but won't block the pinning if it's below 10.

When a new cluster member comes online, the cluster would reevaluate which pins are below the minimum redundancy and add the new member to the allocation list.