facebook tao system.
single leader replication.
OT, operational transaction
write through cache, read through cache
ddia figure 5-8
Conflict-free replicated data type
distributed lock -> distributed cache, chubby
read after write, cascading rollback
write after read, non repeatable read.
ACID vs BASE
cockroachDB vs spanner
compare and swap
redis sync replication, use wait timeout，still can’t gurantee strong consistency.
Chandy Lamport algo, 增量snapshot, which is used by flink
WAL, use UPS to keep not down.
snapshot is actually compact for WAL.
zookeeper, need to review, how the CP works.
consensus, agree on one result
3 roles: proposers, acceptors, learners
single node can take multiple roles, all all of roles.