ZOOKEEPER-3781: Create snapshots on followers when snapshot.trust.empty is true #111
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…ty is true snapshot.trust.empty is an escape hatch for users upgrading from 3.4.x to later Zookeeper versions, allowing nodes to start with a non-empty transaction log but no snapshot. The intent is for this setting to be enabled for a short while during the upgrade, and then disabled again, as the check it disables is a safety feature. Prior to this PR, a node would only write a snapshot locally if it became leader, or if it had fallen so far behind the leader that the leader sent a SNAP message instead of a DIFF. This made the upgrade process inconvenient, as not all nodes would create a snapshot when snapshot.trust.empty was true, meaning that the safety check could not be flipped back on. This PR makes follower nodes write a local snapshot when they receive NEWLEADER, if they have no local snapshot and snapshot.trust.empty is true. Author: Stig Rohde Døssing <[email protected]> Reviewers: Enrico Olivelli <[email protected]>, Damien Diederen <[email protected]> Closes apache#1581 from srdo/zookeeper-3781
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snapshot.trust.empty is an escape hatch for users upgrading from 3.4.x to later Zookeeper
versions, allowing nodes to start with a non-empty transaction log but no snapshot.
The intent is for this setting to be enabled for a short while during the upgrade,
and then disabled again, as the check it disables is a safety feature.
Prior to this PR, a node would only write a snapshot locally if it became leader,
or if it had fallen so far behind the leader that the leader sent a SNAP message instead
of a DIFF. This made the upgrade process inconvenient, as not all nodes would create
a snapshot when snapshot.trust.empty was true, meaning that the safety check could
not be flipped back on.
This PR makes follower nodes write a local snapshot when they receive NEWLEADER,
if they have no local snapshot and snapshot.trust.empty is true.
Author: Stig Rohde Døssing [email protected]
Reviewers: Enrico Olivelli [email protected], Damien Diederen [email protected]
Closes apache#1581 from srdo/zookeeper-3781