DBOS: A better way to build applications?

Posted by on 29 April, 2024

This post was originally published on this site

At the end of March 2024, Mike Stonebraker announced in a blog post the release of DBOS Cloud, “a transactional serverless computing platform, made possible by a revolutionary new operating system, DBOS, that implements OS services on top of a distributed database.” That sounds odd, to put it mildly, but it makes more sense when you read the origin story:

The idea for DBOS (DataBase oriented Operating System) originated 3 years ago with my realization that the state an operating system must maintain (files, processes, threads, messages, etc.) has increased in size by about 6 orders of magnitude since I began using Unix on a PDP-11/40 in 1973. As such, storing OS state is a database problem. Also, Linux is legacy code at the present time and is having difficulty making forward progress. For example there is no multi-node version of Linux, requiring people to run an orchestrator such as Kubernetes. When I heard a talk by Matei Zaharia in which he said Databricks could not use traditional OS scheduling technology at the scale they were running and had turned to a DBMS solution instead, it was clear that it was time to move the DBMS into the kernel and build a new operating system.”

If you don’t know Stonebraker, he’s been a database-focused computer scientist (and professor) since the early 1970s, when he and his UC Berkeley colleagues Eugene Wong and Larry Rowe founded Ingres. Ingres later inspired Sybase, which was eventually the basis for Microsoft SQL Server. After selling Ingres to Computer Associates, Stonebraker and Rowe started researching Postgres, which later became PostgreSQL and also evolved into Illustra, which was purchased by Informix.

I heard Stonebraker talk about Postgres at a DBMS conference in 1980. What I got out of that talk, aside from an image of “jungle drums” calling for SQL, was the idea that you could add support for complex data types to the database by implementing new index types, extending the query language, and adding support for that to the query parser and optimizer. The example he used was geospatial information, and he explained one kind of index structure that would make 2D geometric database queries go very fast. (This facility eventually became PostGIS. The R-tree currently used by default in PostGIS GiST indexes wasn’t invented until 1984, so Mike was probably talking about the older quadtree index.)

Skipping ahead 44 years, it should surprise precisely nobody in the database field that DBOS uses a distributed version of PostgreSQL as its kernel database layer.

dbos 01 IDG

The DBOS system diagram makes it clear that a database is part of the OS kernel. The distributed database relies on a minimal kernel, but sits under the OS services instead of running in the application layer as a normal database would.

DBOS features

DBOS Transact, an open-source TypeScript framework, supports Postgres-compatible transactions, reliable workflow orchestration, HTTP serving using GET and POST, communication with external services and third-party APIs, idempotent requests using UUID keys, authentication and authorization, Kafka integration with exactly-once semantics, unit testing, and self-hosting. DBOS Cloud, a transactional serverless platform for deploying DBOS Transact applications, supports serverless app deployment, time-travel debugging, cloud database management, and observability.

Let’s highlight some major areas of interest.

DBOS Transact

The code shown in the screenshot below demonstrates transactions, as well as HTTP serving using GET. It’s worthwhile to read the code closely. It’s only 18 lines, not counting blank lines.

The first import (line 1) brings in the DBOS SDK classes that we’ll need. The second import (line 2) brings in the Knex.js SQL query builder, which handles sending the parameterized query to the Postgres database and returning the resulting rows. The database table schema is defined in lines 4 through 8; the only columns are a name string and a greet_count integer.

There is only one method in the Hello class, helloTransaction. It is wrapped in @GetApi and @Transaction decorators, which respectively cause the method to be served in response to an HTTP GET request on the path /greeting/ followed by the username parameter you want to pass in and wrap the database call in a transaction, so that two instances can’t update the database simultaneously.

The database query string (line 16) uses PostgreSQL syntax to try to insert a row into the database for the supplied name and an initial count of 1. If the row already exists, then the ON CONFLICT trigger runs an update operation that increments the count in the database.

Line 17 uses Knex.js to send the SQL query to the DBOS system database and retrieves the result. Line 18 pulls the count out of the first row of results and returns the greeting string to the calling program.

The use of SQL and a database for what feels like should be a core in-memory system API, such as a Linux atomic counter or a Windows interlocked variable, seems deeply weird. Nevertheless, it works.

dbos 02 IDG

This TypeScript code for a Hello class is generated when you perform a DBOS create operation. As you can see, it relies on the @GetApi and @Transaction decorators to serve the function from HTTP GET requests and run the function as a database transaction.

DBOS Time Travel Debugger

When you run an application in DBOS Cloud it records every step and change it makes (the workflow) in the database. You can debug that using Visual Studio Code and the DBOS Time Travel Debugger extension. The time-travel debugger allows you to debug your DBOS application against the database as it existed at the time the selected workflow originally executed.

dbos 03IDG

To perform time-travel debugging, you first start with a CodeLens to list saved trace workflows. Once you choose the one you want, you can debug it using Visual Studio Code with a plugin, or from the command line.

dbos 04IDG

Time-travel debugging with a saved workflow looks very much like ordinary debugging in Visual Studio Code. The code being debugged is the same Hello class you saw earlier. 

DBOS Quickstart

The DBOS Quickstart tutorial requires Node.js 20 or later and a PostgreSQL database you can connect to, either locally, in a Docker container, or remotely. I already had Node.js v20.9.0 installed on my M1 MacBook, but I upgraded it to v20.12.1 from the Node.js website.

I didn’t have PostgreSQL installed, so I downloaded and ran the interactive installer for v16.2 from EnterpriseDB. This installer creates a full-blown macOS server and applications. If I had used Homebrew instead, it would have created command-line applications, and if I had used Postgres.app, I would have gotten a menu-bar app.

The Quickstart proper starts by creating a DBOS app directory using Node.js.

martinheller@Martins-M1-MBP ~ % npx -y @dbos-inc/create@latest -n myapp
Merged .gitignore files saved to myapp/.gitignore
added 590 packages, and audited 591 packages in 25s
found 0 vulnerabilities
added 1 package, and audited 592 packages in 1s
found 0 vulnerabilities
added 129 packages, and audited 721 packages in 5s
found 0 vulnerabilities
Application initialized successfully!

Then you configure the app to use your Postgres server and export your Postgres password into an enviroment variable.

martinheller@Martins-M1-MBP ~ % cd myapp
martinheller@Martins-M1-MBP myapp % npx dbos configure
? What is the hostname of your Postgres server? localhost
? What is the port of your Postgres server? 5432
? What is your Postgres username? postgres
martinheller@Martins-M1-MBP myapp % export PGPASSWORD=*********

After that, you create a “Hello” database using Node.js and Knex.js.

martinheller@Martins-M1-MBP myapp % npx dbos migrate
2024-04-09 15:01:42 [info]: Starting migration: creating database hello if it does not exist
2024-04-09 15:01:42 [info]: Database hello does not exist, creating...
2024-04-09 15:01:42 [info]: Executing migration command: npx knex migrate:latest
2024-04-09 15:01:43 [info]: Batch 1 run: 1 migrations
2024-04-09 15:01:43 [info]: Creating DBOS tables and system database.
2024-04-09 15:01:43 [info]: Migration successful!

With that complete, you build and run the DBOS app locally.

martinheller@Martins-M1-MBP myapp % npm run build
npx dbos start

> myapp@0.0.1 build
> tsc

2024-04-09 15:02:30 [info]: Workflow executor initialized
2024-04-09 15:02:30 [info]: HTTP endpoints supported:
2024-04-09 15:02:30 [info]:     GET   :  /greeting/:user
2024-04-09 15:02:30 [info]: DBOS Server is running at http://localhost:3000
2024-04-09 15:02:30 [info]: DBOS Admin Server is running at http://localhost:3001

At this point, you can browse to http://localhost:3000 to test the application. That done, you register for the DBOS Cloud and provision your own database there.

martinheller@Martins-M1-MBP myapp % npx dbos-cloud register -u meheller
2024-04-09 15:11:35 [info]: Welcome to DBOS Cloud!
2024-04-09 15:11:35 [info]: Before creating an account, please tell us a bit about yourself!
Enter First/Given Name: Martin
Enter Last/Family Name: Heller
Enter Company: self
2024-04-09 15:12:06 [info]: Please authenticate with DBOS Cloud!
Login URL: https://login.dbos.dev/activate?user_code=QWKW-TXTB
2024-04-09 15:12:12 [info]: Waiting for login...
2024-04-09 15:12:17 [info]: Waiting for login...
2024-04-09 15:12:22 [info]: Waiting for login...
2024-04-09 15:12:27 [info]: Waiting for login...
2024-04-09 15:12:32 [info]: Waiting for login...
2024-04-09 15:12:38 [info]: Waiting for login...
2024-04-09 15:12:44 [info]: meheller successfully registered!
martinheller@Martins-M1-MBP myapp % npx dbos-cloud db provision iw_db -U meheller
Database Password: ********
2024-04-09 15:19:22 [info]: Successfully started provisioning database: iw_db
2024-04-09 15:19:28 [info]: {"PostgresInstanceName":"iw_db","HostName":"userdb-51fcc211-6ed3-4450-a90e-0f864fc1066c.cvc4gmaa6qm9.us-east-1.rds.amazonaws.com","Status":"available","Port":5432,"DatabaseUsername":"meheller","AdminUsername":"meheller"}
2024-04-09 15:19:28 [info]: Database successfully provisioned!

Finally, you can register and deploy your app in the DBOS Cloud.

martinheller@Martins-M1-MBP myapp % npx dbos-cloud app register -d iw_db
2024-04-09 15:20:09 [info]: Loaded application name from package.json: myapp
2024-04-09 15:20:09 [info]: Registering application: myapp
2024-04-09 15:20:11 [info]: myapp ID: d8806829-c5b8-4df0-8b5a-2d1bf87c3322
2024-04-09 15:20:11 [info]: Successfully registered myapp!
martinheller@Martins-M1-MBP myapp % npx dbos-cloud app deploy
2024-04-09 15:20:35 [info]: Loaded application name from package.json: myapp
2024-04-09 15:20:35 [info]: Submitting deploy request for myapp
2024-04-09 15:21:09 [info]: Submitted deploy request for myapp. Assigned version: 1712676035
2024-04-09 15:21:13 [info]: Waiting for myapp with version 1712676035 to be available
2024-04-09 15:21:21 [info]: Successfully deployed myapp!
2024-04-09 15:21:21 [info]: Access your application at https://meheller-myapp.cloud.dbos.dev/
dbos 05IDG

The “Hello” application running in the DBOS Cloud counts every greeting. It uses the code you saw earlier.

DBOS applications

The “Hello” application does illustrate some of the core features of DBOS Transact and the DBOS Cloud, but it’s so basic that it’s barely a toy. The Programming Quickstart adds a few more details, and it’s worth your time to go through it. You’ll learn how to use communicator functions to access third-party services (email, in this example) as well as how to compose reliable workflows. You’ll literally interrupt the workflow and restart it without re-sending the email: DBOS workflows always run to completion and each of their operations executes once and only once. That’s possible because DBOS persists the output of each step in your database.

Once you’ve understood the programming Quickstart, you’ll be ready to try out the two DBOS demo applications, which do rise to the level of being toys. Both demos use Next.js for their front ends, and both use DBOS workflows, transactions, and communicators.

The first demo, E-Commerce, is a web shopping and payment processing system. It’s worthwhile reading the Under the Covers section of the README in the demo’s repository to understand how it works and how you might want to upgrade it to, for example, use a real-world payment provider.

The second demo, YKY Social, simulates a simple social network, and uses TypeORM rather than Knex.js for its database code. It also uses Amazon S3 for profile photos. If you’re serious about using DBOS yourself, you should work though both demo applications.

A tantalizing glimpse

I have to say that DBOS and DBOS Cloud look very interesting. Reliable execution and time-travel debugging, for example, are quite desirable. On the other hand, I wouldn’t want to build a real application on DBOS or DBOS Cloud at this point. I have lots of questions, starting with “How does it scale in practice?” and probably ending with “How much will it cost at X scale?”

I mentioned earlier that DBOS code looks weird but works. I would imagine that any programming shop considering writing an application on it would be discouraged or even repelled by the “it looks weird” part, as developers tend to be set in their ways until what they are doing no longer works.

I also have to point out that the current implementation of DBOS is very far from the system diagram you saw near the beginning of this review. Where’s the minimal kernel? DBOS currently runs on macOS, Linux, and Windows. None of those are minimal kernels. DBOS Cloud currently runs on AWS. Again, not a minimal kernel.

So, overall, DBOS is a tantalizing glimpse of something that may eventually turn out to be cool. It’s new and shiny, and it comes from smart people, but it will be awhile before it could possibly become a mainstream system.

Cost: Free with usage limits; paid plans require you to contact sales.

Platform: macOS, Linux, Windows, AWS.

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