Fencing token.

also: fencing tokens · epoch number · epoch numbers · generation ID · generation IDs

A number that increases with every new leader or lock holder; resources reject requests carrying an older token than they've seen.

the two-minute refresher

Every election (or lock grant) increments a global counter: 33, then 34.
The holder sends its token with each write; the storage remembers the highest token seen.
An old leader waking from a GC pause with token 33 is rejected after 34 has written.
Timeouts alone can't prevent this; the resource itself must check.

also: fencing tokens · epoch number · epoch numbers · generation ID · generation IDs

A number that increases with every new leader or lock holder; resources reject requests carrying an older token than they've seen.

Every election (or lock grant) increments a global counter: 33, then 34.
The holder sends its token with each write; the storage remembers the highest token seen.
An old leader waking from a GC pause with token 33 is rejected after 34 has written.
Timeouts alone can't prevent this; the resource itself must check.