facilitator Dockerfile

Adds a Dockerfile that builds the facilitator in a minimal Alpine Linux
container, then packages the statically linked binary into another
Alpine Linux container. Also adds a `docker build` step to CI build.

.github/workflows/ci-build.yml

@@ -10,12 +10,11 @@ on:
 env:
   CARGO_TERM_COLOR: always
 
-defaults:
-  run:
-    working-directory: facilitator
-
 jobs:
   build-rust:
+    defaults:
+      run:
+        working-directory: facilitator
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
@@ -25,3 +24,13 @@ jobs:
       run: cargo build --verbose
     - name: Run tests
       run: cargo test --verbose
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Docker build
+      uses: docker/setup-buildx-action@v1
+    - name: build
+      uses: docker/build-push-action@v2
+      with:
+        file: facilitator/Dockerfile

facilitator/Dockerfile

@@ -0,0 +1,16 @@
+FROM rust:1.46-alpine as builder
+
+RUN apk add libc-dev && apk update
+
+WORKDIR /usr/src/prio-server
+# We enumerate these paths so that `docker build` fails in an obvious way if run
+# from the wrong place.
+COPY ./avro-schema ./avro-schema
+COPY ./facilitator ./facilitator
+
+RUN cargo install --path ./facilitator
+
+FROM rust:1.46-alpine
+RUN apk update
+COPY --from=builder /usr/local/cargo/bin/facilitator /usr/local/bin/facilitator
+ENTRYPOINT ["/usr/local/bin/facilitator"]

facilitator/README.md

@@ -4,12 +4,16 @@ This is ISRG's implementation of a Prio accumulation server. It ingests a share
 
 ## Getting started
 
-[Install a Rust toolchain](https://www.rust-lang.org/tools/install), then just `cargo build|run|test`.
+[Install a Rust toolchain](https://www.rust-lang.org/tools/install), then just `cargo build|run|test`. See `cargo run -- --help` for information on the various options and subcommands.
 
 ## Generating ingestion data
 
 To generate sample ingestion data, see the `generate-ingestion-sample` command and its usage (`cargo run -- generate-ingestion-sample --help`).
 
+## Docker
+
+To build a Docker image, try `docker build -t my-image-repository/facilitator:x.y.z -f facilitator/Dockerfile .` *from the root directory of `prio-server`*. This is important because building `facilitator` depends on the schema files in `avro-schema`.
+
 ## References
 
 [Prio Data Share Batch IDL](https://docs.google.com/document/d/1L06dpE7OcC4CXho2UswrfHrnWKtbA9aSSmO_5o7Ku6I/edit#heading=h.3kq1yexquq2g)