- Upgrading from 0.18 requires issuing a full flush of all the indices in the cluster (
curl host:9200/_flush) before shutting down the cluster, with no indexing operations happening after the flush.
- The local gateway state structure has changed, a backup of the state files is created when upgrading, they can then be used to downgrade back to 0.18. Don’t downgrade without using them.
- Avoid placing a shard replica on the same machine as shard itself (#1680)
- GC logging: Enable back automatic gc logging based on thresholds (even if last gc is not available) (#1679)
- Index API: Don’t wait for new mappings to be applied on the cluster by default (#1677)
- Nodes Info API: Add
all flag to return all data (#1676)
- Transport buffer overrun can happen because of byte buffer reading optimization introduced in 0.19.0.RC1 (#1686)