Transmode/gradle-docker

A Gradle plugin to build Docker images from the build script.

Dave Syer

@dsyer

That might be useful in general

Specifically for this guide we want to have the same Dockerfile work for Maven and Gradle (I know it's slightly artificial, but we always try and support both)

In the Maven plugin as soon as you use an external Dockerfile everything else is ignored

So maybe I prefer your approach slightly, but we still have to work around one or the other

Matthias Grüter

@mattgruter

Ok, I see. Looking at the guide right now.

So you're copying your jar file into the docker stageDir (build/docker) manually.

Dave Syer

@dsyer

Yes

And that also means we have to define a custom task

Matthias Grüter

@mattgruter

Wouldn't something like:

copy {
    from jar
    into stageDir
}

work?

Dave Syer

@dsyer

and that it has to be deferred with "<<"

I'm not a gradler. Happy to take edits.

Where does that go?

Inside the task definition?

Matthias Grüter

@mattgruter

Yes, instead of the new File(stageDir, jar.archiveName).bytes = jar.archivePath.bytes

Dave Syer

@dsyer

Trying it...

Dave Syer

@dsyer

I don't think that worked

the image it builds has the same ID as docker/java

Actually that's a problem with the "<<" (cc @gregturn)

Matthias Grüter

@mattgruter

Exactly. The dockerfile, applicationName and push properties have to be defined in the configuration phase of the build not the execution phase (with the "<<" you push everything into the execution phase)

Dave Syer

@dsyer

Yeah. I'm unhacking that now.

Then the copy{} works, thanks

Matthias Grüter

@mattgruter

This should work:

task buildDocker(type: Docker, dependsOn: jar) {
  push = false
  applicationName = jar.baseName
  dockerfile = file('src/main/docker/Dockerfile')
  doFirst {
    copy {
      from jar
      into stageDir
    }
  } 
}

Dave Syer

@dsyer

@gregturn thought he found a problem that meant he had to defer to execution

It works for me though

Actually that doesn't

You have to "dependsOn: build"

(which I assumed would be the default - haven't tried that yet)

How come I have to explicitly create a java.io.File() for the dockerfile BTW?

Yeah you need "dependsOn: build"

but the copy actually doesn't work

doFirst

Missed that

I hate gradle sometimes

Do you think we could make this use case more mainstream in the plugin? That would help idiots like me.

Dave Syer

@dsyer

New content is available https://spring.io/guides/gs/spring-boot-docker/

It works for me now (on Linux)

Not sure how it affects MacOS users

Matthias Grüter

@mattgruter

yeah, the configuration<>execution build lifecycle stuff is quite confusing in gradle IMO. many bugs lurking there... :-)

Dave Syer

@dsyer

It works now for me anyway, thank you.

Matthias Grüter

@mattgruter

why doesn't dependsOn: jar not work?

Dave Syer

@dsyer

Because the jar that is executable is not built by the gradle "jar" task

It is built by "bootRepackage" (so we could depend on that I guess)

Matthias Grüter

@mattgruter

That would be better, because the task build depends on tests and other findbugs, etc.

Dave Syer

@dsyer

I would expect to want to run tests etc before pushing a container image

It seems like the "last step" in a CI build to me

Matthias Grüter

@mattgruter

True. However, I tend to see buildDocker as a "assembly" step. build then ties together assembly and tests tasks.

Dave Syer

@dsyer

I see.

In which case we will need a custom task here whatever you do in the plugin

Matthias Grüter

@mattgruter

That's mostly a question of taste though. So dependsOn: build is definately ok, especially in a tutorial (short & conscise to read!)

But yeah in general, we should make your use-case more straight-forward with the plugin.

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