[Note]Strong Consistency with Raft and SQLite⌗

https://blog.sqlitecloud.io/strong-consistency-with-raft-and-sqlite

Central Database vs Distributed Database⌗

Advantage:
- It is consistent and up-to-date by default
- Only one source of truth
Disadvantage:
- Single point of failure
- Become overwhelemd as the amount of data grows
- Performance issues
- Slower response times

Advantage:
- Scalability
- High availability
- Localized access Improve response times and reduce network latency
- Lower cost Can be built using commodity hardware

maintain data consistency across multiple nodes

Must be use a strong consistency model

SQLite Cloud guarantees strong consistency and uses the Raft consensus algorithm under the hood

A distrubuted consensus algorithm
Be designed to help manage replicated logs
Works by ensuring that all nodes in a distributed system agree on the same log of commands or events

Leader manage all log
- Works by electing a leader node that manages the replicated log
- Leader node receives commands and replicates them across all nodes
- Ensures that all nodes have the same log of commands by using a series of communication messages called “log entries”
- Each log entry contains a command or event that is appended to the log of each node
Divide time into terms
- Each term begins with a leader election
Log replication
- Leader sends log entries to all other nodes
- A majority vote(quorum)

Leader election
Log replication
Commit mechanisms Ensure that log entries are executed in the same order on all nodes in the system

ChangeSet SQLite Cloud only distribute hte changeset derived from executing the SQL statement in one node

They distribute the result of the statement (plus some other metadata)

{
    "table": foo,
    "data": {
        "col1": 8875612685081594789,
        "col2": "10:57:34",
        "col3": "2023-03-21"
    }
}