App Platform is a Platform-as-a-Service (PaaS) offering that allows developers to publish code directly to DigitalOcean servers without worrying about the underlying infrastructure.
When you give App Platform access to your code, it defaults to using a Dockerfile if one is present in the root of the directory or specified in the app spec. Otherwise, App Platform checks your code to determine what language or framework it uses. If it supports the language or framework, it chooses an appropriate resource type and uses the proper buildpack to build the app and deploy a container.
To make the build system use a Dockerfile during the build process for your app, specify the
dockerfile_path in the app spec:
name: sample-dockerfile services: - name: web git: repo_clone_url: https://github.com/digitalocean/sample-dockerfile.git branch: main dockerfile_path: Dockerfile
To pass environment variables to a Dockerfile-based resource, define them as build-time or run-time environment variables in App Platform. This passes variables down to the
docker build process (with a
--build-arg parameter) and
docker run process (with an
-e parameter) when App Platform builds and deploys your container. You can then access the values of the environment variables using the
ARG keyword in your Dockerfile as you normally would.
Using a Dockerfile to build a Go app is a flexible way to optimize the build image used to deploy the app.
App Platform detects Dockerfile-based Go apps by looking for a
Dockerfile in the root of the directory or by using a path to a
Dockerfile specified in the app spec.
One advantage of a Dockerfile-based build is the ability to reduce the size of the image with multi-stage builds. For example, our sample Dockerfile app uses a multi-stage build so the final container image only contains updated CA certificates and the compiled Go binary:
# This is a standard Dockerfile for building a Go app. # It is a multi-stage build: the first stage compiles the Go source into a binary, and # the second stage copies only the binary into an alpine base. # -- Stage 1 -- # # Compile the app. FROM golang:1.12-alpine as builder WORKDIR /app # The build context is set to the directory where the repo is cloned. # This will copy all files in the repo to /app inside the container. # If your app requires the build context to be set to a subdirectory inside the repo, you # can use the source_dir app spec option, see: <https://www.digitalocean.com/docs/app-platform/reference/app-specification-reference/> COPY . . RUN go build -mod=vendor -o bin/hello # -- Stage 2 -- # # Create the final environment with the compiled binary. FROM alpine # Install any required dependencies. RUN apk --no-cache add ca-certificates WORKDIR /root/ # Copy the binary from the builder stage and set it as the default command. COPY --from=builder /app/bin/hello /usr/local/bin/ CMD ["hello"]
/var/runas a special path and avoids extracting it from base Docker images. This may cause errors with some builds. To resolve, restore
/var/runin the form that is expected by the base image. For example, with Alpine Linux base images:
RUN test -e /var/run || ln -s /run /var/run.
gunicorn --worker-tmp-dir /dev/shm project.wsgi, where
projectis the name of your project.