TLDR: publishTask first triggers publishLocalTask which runs docker build even for multiplatform builds that require docker buildx build; docker buildx build is only triggered in the publishTask later. I'd guess that dockerBuildCommand should check dockerBuildxPlatforms to select between build and buildx build such that publishLocal issues a single build, and publish just pushes the tags from the local build instead of triggering a new build.
Multiplatform builds require using buildx with the docker-container driver, which I am doing
I have modified stage0 to include a layer that builds a binary (not the easiest thing since #1417 is open and #1437 was closed without comment). This layer is now a slow process and so I want the layer cached. Because this is only in stage0 the layer is not included in the final docker image publish. The way to solve this is to add --cache-to and --cache-from such that even intermediate layers get cached and reused
[error] ERROR: cache export feature is currently not supported for docker driver. Please switch to a different driver (eg. "docker buildx create --use")
[info] Removing intermediate image(s) (labeled "snp-multi-stage-id=739842cd-6d16-4c12-8195-67def738cf32")
[info] Total reclaimed space: 0B
[error] java.lang.RuntimeException: Nonzero exit value: 1
[error] at com.typesafe.sbt.packager.docker.DockerPlugin$.publishLocalDocker(DockerPlugin.scala:691)
[error] at com.typesafe.sbt.packager.docker.DockerPlugin$.$anonfun$projectSettings$42(DockerPlugin.scala:267)
[error] at com.typesafe.sbt.packager.docker.DockerPlugin$.$anonfun$projectSettings$42$adapted(DockerPlugin.scala:259)
This is unexpected and means publishLocalDocker is using the docker driver and not using buildx with the docker-container driver I set.
Indeed, publishLocalDocker is called in publishLocalTask with
And publishLocalTask is invoked as the first step in publishTask with val _ = publishLocal.value. At this point, dockerBuildCommand is docker build ... and dockerExecCommand is docker. Only later in publishTask does it check for a multiplatform build and alter the exec command to be docker buildx build ... --push.
This results in a docker build for the host architecture using the docker driver, followed by a docker buildx build for any configured platforms. In the presence of --cache-from and --cache-to, the initial docker build fails. If the host architecture matches a configured cross-platform, the docker buildx build will reuse those layers, and if not then the docker build is wasted work.
This can be worked around by resetting dockerBuildCommand:
TLDR:
publishTaskfirst triggerspublishLocalTaskwhich runsdocker buildeven for multiplatform builds that requiredocker buildx build;docker buildx buildis only triggered in thepublishTasklater. I'd guess thatdockerBuildCommandshould checkdockerBuildxPlatformsto select betweenbuildandbuildx buildsuch thatpublishLocalissues a single build, andpublishjust pushes the tags from the local build instead of triggering a new build.Multiplatform builds require using
buildxwith thedocker-containerdriver, which I am doingI have modified
stage0to include a layer that builds a binary (not the easiest thing since #1417 is open and #1437 was closed without comment). This layer is now a slow process and so I want the layer cached. Because this is only instage0the layer is not included in the final docker image publish. The way to solve this is to add--cache-toand--cache-fromsuch that even intermediate layers get cached and reusedRunning this setup results in an error
This is unexpected and means
publishLocalDockeris using thedockerdriver and not usingbuildxwith thedocker-containerdriver I set.Indeed,
publishLocalDockeris called inpublishLocalTaskwithAnd
publishLocalTaskis invoked as the first step inpublishTaskwithval _ = publishLocal.value. At this point,dockerBuildCommandisdocker build ...anddockerExecCommandisdocker. Only later inpublishTaskdoes it check for a multiplatform build and alter the exec command to bedocker buildx build ... --push.This results in a
docker buildfor the host architecture using thedockerdriver, followed by adocker buildx buildfor any configured platforms. In the presence of--cache-fromand--cache-to, the initialdocker buildfails. If the host architecture matches a configured cross-platform, thedocker buildx buildwill reuse those layers, and if not then thedocker buildis wasted work.This can be worked around by resetting
dockerBuildCommand:It is only a workaround since
buildx buildgets invoked twice, but at least the second time is already cached locally.Expected behaviour
Multiplatform builds consistently use
docker buildx buildand only build onceActual behaviour
Multiplatform builds start with a
docker buildand later issue adocker buildx buildInformation