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Build wgrib2 in Docker with cached build stage

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Add a separate wgrib2-builder stage that compiles wgrib2 from source.
Docker layer caching means this only builds once — subsequent deploys
reuse the cached layer. The binary is copied into the final runtime
image. Also fixed wgrib2 path lookup to be runtime instead of
compile-time so it works in the Docker build pipeline.
This commit is contained in:
Graham McIntire 2026-03-31 08:55:09 -05:00
parent 66639e3717
commit 4e2d74e21c
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GPG key ID: F4ABF488E6029E59
2 changed files with 34 additions and 8 deletions
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33
Dockerfile
View file

@ -18,6 +18,29 @@ ARG DEBIAN_VERSION=trixie-20260316-slim
ARG BUILDER_IMAGE="docker.io/hexpm/elixir:${ELIXIR_VERSION}-erlang-${OTP_VERSION}-debian-${DEBIAN_VERSION}"
ARG RUNNER_IMAGE="docker.io/debian:${DEBIAN_VERSION}"
# ---- wgrib2 build stage (cached independently) ----
FROM ${RUNNER_IMAGE} AS wgrib2-builder
ARG WGRIB2_VERSION=3.6.1
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
build-essential gfortran wget ca-certificates \
zlib1g-dev libaec-dev libpng-dev \
&& rm -rf /var/lib/apt/lists/*
WORKDIR /tmp/wgrib2
RUN wget -q "https://www.ftp.cpc.ncep.noaa.gov/wd51we/wgrib2/wgrib2.tgz.v${WGRIB2_VERSION}" \
-O wgrib2.tgz \
&& tar xzf wgrib2.tgz \
&& cd grib2 \
&& export CC=gcc FC=gfortran \
&& make \
&& cp wgrib2/wgrib2 /usr/local/bin/wgrib2 \
&& strip /usr/local/bin/wgrib2
# ---- Elixir build stage ----
FROM ${BUILDER_IMAGE} AS builder
# install build dependencies
@ -66,12 +89,13 @@ COPY config/runtime.exs config/
COPY rel rel
RUN mix release
# start a new build stage so that the final image will only contain
# the compiled release and other runtime necessities
# ---- Final runtime stage ----
FROM ${RUNNER_IMAGE} AS final
RUN apt-get update \
&& apt-get install -y --no-install-recommends libstdc++6 openssl libncurses6 locales ca-certificates snmp \
&& apt-get install -y --no-install-recommends \
libstdc++6 openssl libncurses6 locales ca-certificates snmp \
libgfortran5 libaec0 zlib1g libpng16-16t64 \
&& rm -rf /var/lib/apt/lists/*
# Set the locale
@ -88,6 +112,9 @@ RUN chown nobody /app
# set runner ENV
ENV MIX_ENV="prod"
# Copy wgrib2 binary from the build stage
COPY --from=wgrib2-builder /usr/local/bin/wgrib2 /usr/local/bin/wgrib2
# Only copy the final release from the build stage
COPY --from=builder --chown=nobody:root /app/_build/${MIX_ENV}/rel/microwaveprop ./

9
lib/microwaveprop/weather/grib2/wgrib2.ex
View file

@ -9,7 +9,6 @@ defmodule Microwaveprop.Weather.Grib2.Wgrib2 do
require Logger
@wgrib2_path System.find_executable("wgrib2")
@undefined_value 9.999e20
@doc """
@ -29,9 +28,9 @@ defmodule Microwaveprop.Weather.Grib2.Wgrib2 do
end
@doc "Check if wgrib2 is available on the system."
def available? do
@wgrib2_path != nil
end
def available?, do: wgrib2_path() != nil
defp wgrib2_path, do: System.find_executable("wgrib2")
defp extract_with_wgrib2(grib_binary, match_pattern, grid_spec) do
%{
@ -68,7 +67,7 @@ defmodule Microwaveprop.Weather.Grib2.Wgrib2 do
"bin"
]
case System.cmd(@wgrib2_path, args, stderr_to_stdout: true) do
case System.cmd(wgrib2_path(), args, stderr_to_stdout: true) do
{output, 0} ->
# Parse message inventory from stdout to know which vars were extracted
messages = parse_wgrib2_inventory(output)