[0] https://jira.mongodb.org/browse/SERVER-57476
[1] https://jira.mongodb.org/browse/SERVER-56779
2: Do not use the collection distributed lock for chunk merges
https://jepsen.io/analyses/mongodb-4.2.6
https://news.ycombinator.com/item?id=23290844
https://news.ycombinator.com/item?id=23285249