Show HN: DBOS Java – Postgres-Backed Durable Workflows

114 pointsposted 3 months ago
by KraftyOne

41 Comments

reecardo

3 months ago

We are increasingly using Temporal with Temporal Cloud and soon Nexus to manage numerous workflows. I'm curious what type of observability is avialable for DBOS and how much of that you get for "free". The reason we ended up in Temporal was not that previous job-systems were unreliable, it was simply that nobody wanted to go dig through a database to find out what happened with their job, and nobody has time/energy to build a UI just for that purpose.

KraftyOne

3 months ago

There's an observability and workflow management UI: https://docs.dbos.dev/java/tutorials/workflow-management

You can view your workflows and queues, search/filter them by any number of criteria, visualize graphs of workflow steps, cancel workflows, resume workflows, restart workflows from a specific step--everything you'd want.

Currently, this is available as a managed offering (Conductor - https://docs.dbos.dev/production/self-hosting/conductor), but we're also releasing a self-hostable version of it soon.

exabrial

3 months ago

The Java version looks pretty danged cool paging through the some of the code.

I was trying to think of a use case for this and I was reminded of a Sun Microsystems demo (yes I'm that old) I saw. The paused a JVM and "slept" it, then kicked up on another machine almost instantly, all over the network. Was a pretty cool party trick, but then they did it when an HTTP request came in (Serverless was invented a LONG time ago!). I kinda wonder if this could be used for that?

KraftyOne

3 months ago

Haha yes, one thing you can use this for is "long waits" or "long sleeps" where a program waits hours or days or weeks for a notification (potentially through server restarts, etc) then wakes up as soon as the notification arrives or a timeout is reached. More info in the docs: https://docs.dbos.dev/java/tutorials/workflow-communication

jedberg

3 months ago

> I was reminded of a Sun Microsystems demo (yes I'm that old)

I wonder if my Solaris 7 cert is still good...

ibgeek

3 months ago

I really wish you guys would change the name since the product has moved so far away from the goals and concepts in the original publication. :). I love the product and what you are doing -- it's definitely needed and valuable.

jedberg

3 months ago

We’ve considered it, but at this point we’re kind of stuck. We’d have to rebuild our brand from scratch. But also, a name almost never makes or breaks a company. :)

Also we have a backronym now: Durable Backends, Observable and Simple.

cowsandmilk

3 months ago

What is the original publication?

rileymichael

3 months ago

glad to see the java sdk released, i've been following it for a while.

one of the rough edges i've noticed w/DBOS is for workflows that span multiple services. all of the examples are contained in a single application and thus use a single dbos 'system db' instance. if you have multiple services (as you often do in the real world) that need to participate in a workflow.. you really can't. you need to break them into multiple workflows and enqueue them in each service by creating an instance of the dbos client pointed at the other services system db. aside from the obvious overhead from fragmenting a workflow into multiple (and that you have to push to the service instead of a worker pulling the step), that means that every service needs to be aware of and have access to, every other services system db. also worth noting that sharing a single system db between services was not advised when i asked.

(docs for the above: https://docs.dbos.dev/architecture#using-dbos-in-a-distribut...)

jedberg

3 months ago

The pattern I would recommend in such cases is having one service be responsible for the overall workflow and then call the other services as steps.

So if you were for example running a website and wanted to have a "cancellation" flow, you'd have the cancellation service with the workflow inside of it, which would have all the steps defined, like

1) disable user account

2) mark user data as archived

3) cancel recurring payments

And then each step would call the service that actually does that work, using an idempotency key. Each service might have its own internal workflows to accomplish each task. In this case step 1 would call the accounts service, step two would call the storage service, and step three would call the payment service.

But then you have a clean reusable interface in each service, as well as a single service responsible for the workflow.

KraftyOne

3 months ago

Thanks for the great feedback! Yeah, for isolation we recommend each service have its own system database and communicate via clients (so service A starts a workflow in service B by creating a client and calling "client.enqueue").

How could we make this experience better while keeping DBOS a simple library? One improvement that comes to mind is to add an "application name" field to the workflows table so that multiple applications could share a system database. Then one application could directly enqueue a workflow to another application by specifying its name, and workflow observability tooling would work cross-application.

ivanr

3 months ago

Hello Peter. Thank you for your work. I really like this approach. I too have been following Temporal and I like it, but I don't think it's a good match for simpler systems.

I've been reading the DBOS Java documentation and have some questions, if you don't mind:

- Versioning; from the looks of it, it's either automatically derived from the source code (presumably bytecode?), or explicitly set for the entire application? This would be too coarse. I don't see auto-configuration working, as a small bug fix would invalidate the version. (Could be less of a problem if you're looking only at method signatures... perhaps add to the documentation?) Similarly, for the explicit setting, a change to the version number would invalidate all existing workflows, which would be cumbersome.

Have you considered relying on serialVersionUID? Or at least allowing explicit configuration on a per workflow basis? Or a fallback method to be invoked if the class signatures change in a backward incompatible way?

Overall, it looks like DBOS is fairly easy to pick up, but having a good story for workflow evolution is going to be essential for adoption. For example, if I have long-running workflows... do I have to keep the old code running until all old instances complete? Is that the idea?

- Transactional use; would it be possible to create a new workflow instance transactionally? If I am using the same database for DBOS and my application, I'd expect my app to do some work and create some jobs for later, reusing my transaction. Similarly, maybe when the jobs are running, I'd perhaps want to use the same transaction? As in, the work is done and then DBOS commits?

I know using the same transaction for both purposes could be tricky. I have, in fact, in the past, used two for job handling. Some guidance in the documentation would be very useful to have.

Thank you.

KraftyOne

3 months ago

Thanks for the great questions!

1. Yes, currently versioning is either automatically derived from a bytecode hash or manually set. The intended upgrade mechanism is blue-green deployments where old workflows drain on old code versions while new workflows start on new code versions (you can also manually fork workflows to new code versions if they're compatible). Docs: https://docs.dbos.dev/java/tutorials/workflow-tutorial#workf...

That said, we're working on improvements here--we want it to be easier to upgrade your workflows without blue-green deployments to simplify operating really long-running (weeks-months) workflows.

2. Could I ask what the intended use case is? DBOS workflow creation is idempotent and workflows always recover from the last completed step, so a workflow that goes "database transaction" -> "enqueue child workflow" offers the same atomicity guarantees as a workflow that does "enqueue child workflow as part of database transaction", but the former is (as you say) much simpler to implement.

hazn

3 months ago

I remember reading that restate.dev is a 'push' based workflow and therefore works well with serverless workflows: https://news.ycombinator.com/item?id=40660568

what is your input on these two topics? aka pull vs push and working well with serverless workflows

KraftyOne

3 months ago

The Restate model depends on a long-running external orchestrator to do the "pushing". However, that comes with downsides--you have to operate that orchestrator and its data store in production (and it's a single point of failure) and you have to rearchitect your application around it.

DBOS implements a simpler library-based architecture where each of your processes independently "pulls" from a database queue. To make this work in a serverless setting, we recommend using a cron to periodically launch serverless workers that run for as long as there are workflows in the queue. If a worker times out, the next will automatically resume its workflows from their last completed step. This Github discussion has more details: https://github.com/dbos-inc/dbos-transact-ts/issues/1115

layer8

3 months ago

It’s not clear what part of the functionality is specific to Postgres, and why. In particular in the Java world, you would expect any JDBC backend to be able to do the job.

KraftyOne

3 months ago

We actually wrote a blog post recently on why we chose Postgres! https://www.dbos.dev/blog/why-postgres-durable-execution

There's no technical reason why this couldn't be done with another database, and we may add support for more in the future (DBOS Python already supports SQLite), but we're not working on it right now.

prasadaditya

3 months ago

Hey! Not a DBOS Java question but stumbled on this and looking into it for the python client. Wondering what the support looks like for integration w/ gevent?

KraftyOne

3 months ago

DBOS Python works with gevent out of the box (sync DBOS uses Python threading APIs and psycopg3 that gevent monkeypatches).

Have you run into any issues using DBOS Python with gevent? Please let us know!

stankygenki

3 months ago

Upvote on this! Currently building out a project using Flask and gevent, and would love to use DBOS python with my Flask gevent project

xnzm1001

3 months ago

I like dbos architecture much more than temporal since it is much easier to operate on small team.

But dbos doesn't have opensource release of web ui, which is most critical part for a workflow management tool.

Since competitor have all of itself opensource I don't think dbos will have a chance.

jscheel

3 months ago

We are a happy user of DBOS. I’ve been building out a lightweight TUI for managing our DBOS application internally, since we have workflows with tens of thousands of steps. I know the team is working on improving conductor for this use-case, but our internal TUI handles it pretty well for now. Hoping to open source it, but the code is a wreck atm. Anyways, I say all this to say, DBOS has a good client that can communicate with the instance easily, so building out a UI that fits your specific needs should be fairly simple.

KraftyOne

3 months ago

We'll be releasing self-hostable Conductor (the web UI) soon--stay tuned!

nogridbag

3 months ago

Are there any plans for supporting other databases? Our company primarily uses and has experience managing MySQL deployments. I evaluated Temporal some time ago as it seemed like a good fit for what we're building so I'm watching this closely. Thanks!

KraftyOne

3 months ago

Our primary focus is Postgres. DBOS Python recently added SQLite support, we'll add this to other languages if it proves popular, but no current plans for MySQL.

That said, while DBOS requires Postgres for its own checkpoints, it can (and often is) used alongside other databases like MySQL for application data.

user

3 months ago

[deleted]

qianli_cs

3 months ago

To build on what Peter said, we need to stay focused and make one backend solid before expanding. But architecturally, nothing prevents us from supporting more engines going forward.

lukaszkorecki

3 months ago

Looks great, shame that due to annotation-based API it's gonna be a pain to use in Clojure.

KraftyOne

3 months ago

One thing we're looking at right now is what it would take to support Clojure or Kotlin.

rfonseca

3 months ago

Peter, how does this compare to Azure Durable Functions? (Say, for the sake of argument, that you are comparing the Python version of both) Are there things that fundamentally you can do in one and not in the other?

KraftyOne

3 months ago

The main difference is that this is a library you can install and use in any application anywhere, while Durable Functions is (as I understand it) primarily for orchestrating serverless functions in Azure.

stevefan1999

3 months ago

Thanks Peter, but I wonder if there will there be .NET support? Since Temporal includes one, so it is a hard selling point for us .NET developers when MassTransit went commercial.

KraftyOne

3 months ago

.NET support is something we're considering, but aren't actively building right now.

rtcoms

3 months ago

Do you have any plans to support Ruby ?

qianli_cs

3 months ago

Yeah, in the long term, we're supporting more languages. But we aren't actively building new languages right now.