A Look at Bedrock, a Distributed SQLite DB
Julian Brown was introduced to the Bedrock project on an episode of the FLOSS Weekly podcast. He became intrigued enough to look into it a bit further.
Bedrock builds a distributed database layer on top of SQLite3. In the podcast, the argument had been that SQLite was plenty fast and robust enough to be the backend for a single node, and that Bedrock could supply the rest of what you need for distributing the database. Bedrock's main features revolve around replicating the data to all of the nodes, self-healing, and consistency. The system uses master-master replication and is supposed to be fast. Changes to one of the nodes are made as log entries which are automatically shipped to the other nodes and applied. Supposedly, as soon as a new node comes up, it begins to replicate from the other nodes.
In addition to the replication, Bedrock supports a plugin system for extensions. The original story
suggested that SQLite has become more powerful in recent years, so it's up to the challenge. Bedrock
uses an Interface using HTTP to provide the SQL
interface, or supports an
nc-based interface as well.
Julian also pointed out some of the weaknesses of the system that were identified in the podcast and in his research. Since SQLite is designed to be local to a process, there is not really any security. The Bedrock developer kind of hand-waved this as something you would need to provide and it would be protected by your firewall, so it wasn't a big deal. Due to the distributed nature of the system and the fact that SQLite itself supports no low-level coordination between nodes, numeric primary keys are not possible. The authors recommend using UUIDs instead, (which has other benefits).
One interesting point is that it seems to be the backend for Expensify. There did not seem to be any indication that anyone else was using it.
Julian's presentation started out as a pretty straight-forward description of the project. He was not advocating its use, just presenting on the tech. There were several people in the group with knowledge of distributed databases, and also of SQLite. This resulted in a spirited discussion about the viability of the project and whether their claims were reasonable. Those with security backgrounds had questions about protection of access and if there were any features supported to help. The ones with SQLite expertise asked questions about how known deficiencies in SQLite were handled. And pretty much everyone was interested in how edge cases were handled and how far the system had been pushed.
Given that he had not spent a large amount of time trying to do more than get a basic understanding of the technology, Julian was able to answer some questions and direct the rest to the project. The discussion could have been intimidating, but he handled it with grace. And the audience usually realized when they were asking things that only the authors or a search of the code could answer.
It was definitely a lively discussion.
We had 7 people attending this month. As always, we'd like to thank cPanel, Inc. for providing the meeting space and food for the group.