Bedrock

Bedrock is a distributed relational DBMS designed for geo-replication. It uses SQLite as its backing data storage and supports the MySQL wire protocol.

History

BedRock is the system that backs Expensify, the expense management company. It had been used for 8 years prior to being launched. It was originally created as an in house solution to the strict database constraints of financial institutions - response time within milliseconds, transaction logging and authentication, and replication of multiple servers.

Data Model

Relational

Concurrency Control

Multi-version Concurrency Control (MVCC)

Bedrock's synchronization engine is a private distributed general ledger, i.e, a private blockchain. Each thread has an internal table called journal, which has 3 columns called id, query, hash. Each time a query is committed to the database, a new row is inserted into the journal. The new row records the query, and calculates the new incremental hash based on the previous row. When a server connects to a cluster, the most recent id and hash are broadcasted. If two servers disagree on the the hash corresponding to the id, then they know that they have "forked" at some point and stop communicating with each other. A Paxos-based election scheme decides which fork stands up to the new master.

Since Bedrock supports multi-threaded writes, it is prone to write conflicts. This is addressed by "sharding" the table, and querying all the journal tables in a UNION whenever the database is to be viewed as one.

Hardware Acceleration

Custom

Bedrock is written for modern hardware with SSD-backed RAID drives and RAM file caches. It was made to be "simple", not requiring any esoteric hardware hacks as done by other systems. Hence, there is no standard hardware acceleration option.

Query Interface

SQL Command-line / Shell

System Architecture

Shared-Nothing

Indexes

B+Tree

Storage Architecture

Disk-oriented

Bedrock Logo
Website

http://bedrockdb.com/

Source Code

https://github.com/Expensify/Bedrock

Tech Docs

https://github.com/Expensify/Bedrock/tree/master/docs

Developer

Expensify

Country of Origin

US

Start Year

2016

Project Type

Open Source

Written in

C++

Supported languages

C++

Embeds / Uses

SQLite

Inspired By

SQLite

Compatible With

MySQL

Operating Systems

Linux, OS X

Licenses

LGPL v3