Add a container image for the utility and build for it (#7)

PBENCH-1258

.dockerignore

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+# Exclude everything but the listed exceptions.
+*
+!.git
+!LICENSE
+!pyproject.toml
+!README.md
+!src
+!setup.*

.github/workflows/container_build.yml

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+name: Create and publish a Docker image
+
+# Configure this workflow to run every time a change is pushed to a branch
+# whose name starts with `release/` or any time a tag is created; this workflow
+# is also run any time a GitHub release is created or updated ("unpublish" and
+# deletions do not cause it to run).
+on:
+  push:
+    branches: ['release/**']
+    tags: ['*']
+  release:
+    types: [created, edited, prereleased, published, released]
+
+# Set up the container image specification to be `quay.io/pbench/file-relay`.
+env:
+  REGISTRY: quay.io
+  ORGANIZATION: pbench
+  IMAGE_NAME: file-relay
+
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-latest
+
+    # Set the permissions granted to the `GITHUB_TOKEN` for the actions in this job.
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@v2
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_ROBOT_TOKEN }}
+
+      # Extract metadata from the Git reference and the GitHub event.
+      # Subsequent steps can reference the values via `steps.meta.outputs.<key>`.
+      # The `images` value provides the name for the container image which is
+      # used in tags and labels.
+      - name: Extract metadata (tags, labels) from Git for Docker
+        id: meta
+        uses: docker/metadata-action@v4
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.ORGANIZATION }}/${{ env.IMAGE_NAME }}
+
+      # Build the container image based on the Dockerfile and the rest of the
+      # files found in the root of the Git checkout.  If the build succeeds,
+      # the image is pushed to the registry indicated by the tags.
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          file: Dockerfile
+          network: host
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

Dockerfile

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+FROM python:3.9
+LABEL org.opencontainers.image.authors="Pbench Maintainers <[email protected]>"
+
+ENTRYPOINT ["relay"]
+WORKDIR /var/tmp
+
+# Make sure the packaging and installation tools are up to date.
+RUN python3 -m pip install --upgrade pip setuptools wheel
+
+# Copy the files from the context area to a source directory; install the
+# dependencies and the app; and remove the sources.
+COPY . /src/file-relay
+RUN python3 -m pip install -r /src/file-relay/src/requirements.txt /src/file-relay
+RUN rm -rf /src/file-relay