[cedws]

I tried out Dagger hoping to tidy up some of our CI pipelines. I really wasn’t impressed to be honest. I initially just wanted to build a basic Docker image using BuildKit and even that was nightmare that the Dagger guys basically told me just isn’t supported.

[esafak]

When was this; dagger runs on top of buildkit?

[cedws]

Very recently. It may run on BuildKit but it doesn't expose it as a build runtime. IIRC Dagger implements its own way of building images that lacks BuildKit features and doesn't work with Dockerfiles.

[shykes]

Hello! I'm the co-founder of Dagger. It seems that there was a misunderstanding, sorry about that.

Dagger certainly can build a container image natively, without requiring a Dockerfile. It also can build a docker image from a Dockerfile, thanks to a built-in compatibility bridge.

Dagger doesn't expose a raw buildkit socket, but it exposes a cleaner API that has 99% feature parity. Hitting the remaining 1% is rare, but it does happen :) Is there a specific buildkit feature you were looking for? Perhaps we can add it.

Here's an example from the CLI (keeping in mind that there are SDKs for Go, Python, Typescript, PHP and Java with 1-1 feature parity to the CLI):

1. Natively (without Dockerfile):

  #!/usr/bin/env dagger
  
  container |
  from alpine |
  with-exec apk add golang |
  with-directory /src . |
  with-workdir /src |
  with-exec go build |
  publish myregistry.tld/myimage:mytag

2. Build a local directory with Dockerfile:

  #!/usr/bin/env dagger
  
  host |
  directory . |
  docker-build |
  publish myregistry.tld/myimage:mytag

3. Build straight from git remote, with Dockerfile:

  #!/usr/bin/env dagger
  
  git https://github.com/your/repo |
  branch main |
  tree |
  docker-build |
  publish myregistry.tld/myimage:mytag

I hope this helps! Sorry again that you got the wrong impression.

[cedws]

Thanks for your reply. We use BuildKit's cache + SSH socket mounts in most of our Dockerfiles so this was a blocker I came up against immediately when trying Dagger. I'd rather not share my username here but there's a conversation on Discord last month you can dig up (search buildkit in:general) to see what was discussed and proposed solutions.

RE the part about not supporting Dockerfiles - sorry, that was incorrect, I misremembered.

[shykes]

Ah, I see the discussion thread on Discord, thanks.

It looks like you encountered a gap in the Dockerfile compatibility bridge, specifically lack of support for `--mount=type=ssh` [1]. It's true that our Dockerfile compat layer has more gaps than the native Dagger API itself. In effect, beyond very simple Dockerfiles, to get the full benefit of Dagger you need to convert them to code targeting the Dagger API. While there are many benefits to this, it does add significant friction to getting started.

It seems like we need to beef up our compatibility story!

Thanks for taking the time to share all this feedback, and sorry again that your experience didn't work out.

[1] https://github.com/dagger/dagger/issues/6736