Random LABEL snp-multi-stage-id invalidates docker cache

Expected behaviour

I’m currently writing second post about docker cache efficiency on SBT. My main focus is to use docker cache in CI environments as much as possible. Already managed great improvements but there is problem with random generated Labels.

LABEL snp-multi-stage="intermediate"
LABEL snp-multi-stage-id="44857d33-aef2-4d80-b811-7d1ed9b1891d"

Executing second command always invalidates cache which is not always expected. Especially when dockerAutoremoveMultiStageIntermediateImages := false is used. I suggest to use something deterministic like stage0-(packageName in Docker).value

Actual behaviour

Step 1/20 : FROM repo.mycompany.com/team/openjre:8u242 as stage0
[info]  ---> a020ce624573
[info] Step 2/20 : LABEL snp-multi-stage="intermediate"
[info]  ---> Using cache
[info]  ---> 9abeed0b5a9f
[info] Step 3/20 : LABEL snp-multi-stage-id="44857d33-aef2-4d80-b811-7d1ed9b1891d"
[info]  ---> Running in 072dfdce55ad
[info] Removing intermediate container 072dfdce55ad
[info]  ---> 554d25368747
[info] Step 4/20 : WORKDIR /opt/my-app
[info]  ---> Running in 49f3e275dc8c

As you can see cache works with the first label, but gets invalidated after second, random label. @mkurz What do you think about deterministic label?

[an-tex]

If you can live without those labels, it’s possible to simply remove then as a workaround

dockerCommands := dockerCommands.value.filter {
  case Cmd("LABEL", args @ _*) => args.head.startsWith("snp-multi-stage")
  case _                       => true
}

Thanks for the workaround! There’s just a negation missing, it should be: case Cmd("LABEL", args @ _*) => !args.head.startsWith("snp-multi-stage")

In general I believe a deterministic id should be the default. More users are concerned with a fast build compared to ones inspecting their failed builds.

[stoiev]

If you can live without those labels, it’s possible to simply remove then as a workaround

dockerCommands := dockerCommands.value.filter {
  case Cmd("LABEL", args @ _*) => args.head.startsWith("snp-multi-stage")
  case _                       => true
}