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Discussion on: Slim Docker images for your Go application

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victoravelar profile image
Victor Avelar • Edited

Probably not for all the use cases, but you can also use the scratch container

FROM golang as base

WORKDIR /app

ENV GO111MODULE=on \
    CGO_ENABLED=0 \
    GOOS=linux \
    GOARCH=amd64

COPY go.mod .
COPY go.sum .

RUN go mod download

COPY . .

# it will take the flags from the environment
RUN go build

### Certs
FROM alpine:latest as certs
RUN apk --update add ca-certificates

### App
FROM scratch as app
COPY --from=certs /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
COPY --from=base app /
ENTRYPOINT ["/app"]
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So its even smaller than alpine 😄

And it uses and caches modules so the download command will only be executed if something changed either on go.mod or go.sum

Hope it helps!

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krusenas profile image
Karolis

trying to remember what problems I faced with scratch image before I switched to alpine :/ Have you encountered any?

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therealkevinard profile image
Kevin Ard • Edited

Scratch is still my go-to. Only the ssl thing handled here. That reeeeally angered me the first time when I pulled the perfectly crafted images into prod and every. call. failed.

Learned that lesson the hard way 🤷‍♀️

Update: I re-read this dockerfile and I like this one much more than mine. Alright if I borrow that? 😅

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krusenas profile image
Karolis

I think the problem I had was when I needed to do some external linking with C libs :) Then the first example wouldn't have worked either, you then need to use alpine as an initial build image too.

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therealkevinard profile image
Kevin Ard

Scratch is great, but it DEFINITELY depends on your workload. I haven't personally built anything that couldn't run in it, but I'm positive there are limits.

  • my rabbit work queues blaze in scratch.
  • pretty sure basic image manipulation would fail.

Such is scratch lol

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victoravelar profile image
Victor Avelar

Well I think your arguments are very valid, as I said it is not for all the use cases, still we are using it in prod for heavy load micro services and stream producers/consumers and so far its going surprisingly smooth, now I feel very lucky 😂

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therealkevinard profile image
Kevin Ard

Oh, don't get me wrong lol! My scratch-go images... Whoo! I have a single, polymorphic binary that blows my friggin socks off. It's a warehousing pipeline that can produce OR consume billions of records per day from who knows what sources. A damn tank, running on scratch.

Lol but I'd be nervous as crap deploying something that needs imagemagick via a scratch build 🤣

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victoravelar profile image
Victor Avelar

Nothing so far, at least not that I can remember right now. 🤔