ostrich

This package is designed to be a drop-in replacement for a dart based server in a docker image on cloud run for example. This package allows you to get the flutter sdk as we're effectively running a flutter app on the server in docker.

Instead of

void main() async {
  // Do server start
}

void main() => runFlutterServer((context) async {
  // Do server start
});

Benefits

You can now use the dart:ui package
A lot of packages on pub.dev are flutter packages. PDF rendering can now be done with the pdf package.
You can now render via canvas and PictureRecorder
You can use any flutter packages with native plugins that support linux (or whatever platform your using if not docker linux)

Setup (Docker)

# Build the Server
FROM --platform=linux/amd64 dart:stable AS server-builder
ENV FLUTTER_HOME=/flutter
ENV PATH=$FLUTTER_HOME/bin:$PATH

# Install tools required to run flutter & media libraries
RUN apt-get update && apt-get install -y \
    curl git unzip libglu1-mesa clang cmake ninja-build pkg-config libgtk-3-dev \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/* 

# Clone & Install Flutter
RUN git clone https://github.com/flutter/flutter.git $FLUTTER_HOME && \
    flutter channel stable && \
    flutter upgrade --force

# Build the project
WORKDIR /app
COPY pubspec.* ./
COPY . .
RUN flutter pub get
RUN flutter build linux --release

# Server Runtime
FROM --platform=linux/amd64 dart:stable
RUN apt-get update && apt-get install -y \
    wget \
    xvfb \
    libgtk-3-0 \
    libegl1 \
    libgles2 \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/* 

# Install built libraries into final image
RUN ldconfig
WORKDIR /app
COPY --from=server-builder /app/build/linux/x64/release/bundle ./bundle

# You can also make this docker image act as if it were running in GCP
# So you can use all the Google Cloud libraries in a dev environment
# But only add this if your in a dev environment as GCP automatically
# Adds these to the environment. 
### DEV ONLY NOT FOR GCP ###################################################
COPY my-gcp-svc-acct-key.json ./ 
ENV GOOGLE_APPLICATION_CREDENTIALS=/app/my-gcp-svc-acct-key.json
ENV GCP_PROJECT=my-gcp-project-id
############################################################################

# Link libraries to LD path so they are visible on linux
ENV LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib:/usr/lib:

# Find the server executable
RUN find ./bundle -type f -executable ! -name "*.so" -printf "%f\n" > executable_name.txt
EXPOSE 8080

# Run the flutter server with xvfb to simulate a display
CMD xvfb-run -a ./bundle/$(cat executable_name.txt)

Setup (Docker with ImageMagick via FFI)

If you want to use the multimedia package to convert / edit images, we can build a fresh copy of imagemagick and link it to our executable.

Add the multimedia package with flutter pub add multimedia
Add libimage_magick_ffi.so to your project (if its my_server/lib), then place this file in (my_server/ffi/libimage_magick_ffi.so).

Change startup code to load the library

import 'package:ostrich/ostrich.dart';
import 'package:multimedia/multimedia.dart';
   
void main() {
  Future<void> imageMagickLoader = initMultimedia(
    overrideLibrary: File("/app/./bundle/libimage_magick_ffi.so"),
  );
  return runFlutterServer((context) async {
    // You don't need to wait for imageMagickLoader to complete
    // You just need to wait for it to complete before you try
    // to use any multimedia functionality
    await imageMagickLoader; 
    // Do server start
       
    // Do image stuff
    await MediaPipeline([
      MagickImageLoaderJob(File("in.png")),
      ImageOptimizerWebPJob(output: File("image.webp"), maxDimension: 4096, maxBytes: 300 * _kb),
      ImageOptimizerWebPJob(output: File("thumb.webp"), maxDimension: 256, maxBytes: 3 * _kb),
      ImageScaleWebPJob(output: File("low.webp"), maxDimension: 512, quality: 15),
      ImageThumbHashJob(onThumbHash: (h) => th = h),
    ]).push();
  });
}

Define a docker file which builds imagemagick & your server and links it all (uncached builds can take 20+ minutes beware your compiling all image libraries from source)

# Build the Server
FROM --platform=linux/amd64 dart:stable AS server-builder
ENV FLUTTER_HOME=/flutter
ENV PATH=$FLUTTER_HOME/bin:$PATH
   
# Install tools required to run flutter & media libraries
RUN apt-get update && apt-get install -y \
    curl git unzip libglu1-mesa clang cmake ninja-build pkg-config libgtk-3-dev \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/* 
   
# Clone & Install Flutter
RUN git clone https://github.com/flutter/flutter.git $FLUTTER_HOME && \
    flutter channel stable && \
    flutter upgrade --force
   
# Build the project
WORKDIR /app
COPY pubspec.* ./
COPY . .
RUN flutter pub get
RUN flutter build linux --release
   
# Image Magick Capabilities
FROM --platform=linux/amd64 debian:bullseye-slim AS imagemagick-builder
   
# Install tools required to compile libraries for linux
RUN apt-get update && apt-get install -y \
    build-essential \
    wget \
    libltdl-dev \
    libpng-dev \
    libjpeg-dev \
    libtiff-dev \
    libjbig-dev \
    libgomp1 \
    pkg-config \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/* 
   
# Compile ImageMackgic & Libraries
WORKDIR /tmp
RUN wget https://github.com/webmproject/libwebp/archive/refs/tags/v1.4.0.tar.gz \
    && tar xvzf v1.4.0.tar.gz \
    && cd libwebp-1.4.0 \
    && ./autogen.sh \
    && ./configure \
    && make \
    && make install \
    && wget https://github.com/ImageMagick/ImageMagick/archive/refs/tags/7.1.1-39.tar.gz \
    && tar xvzf 7.1.1-39.tar.gz \
    && cd ImageMagick-7.1.1-39 \
    && ./configure --disable-hdri --with-quantum-depth=8 --with-png=yes --with-webp=yes --with-jpeg=yes \
    --with-jp2=yes --without-tiff --with-modules --enable-shared \
    && make \
    && make install 
   
# Server Runtime
FROM --platform=linux/amd64 dart:stable
RUN apt-get update && apt-get install -y \
    wget \
    libltdl-dev \
    libpng-dev \
    libjpeg-dev \
    libtiff-dev \
    libjbig-dev \
    libgomp1 \
    xvfb \
    libgtk-3-0 \
    libegl1 \
    libgles2 \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/* 
   
# Install built libraries into final image
COPY --from=imagemagick-builder /usr/local /usr/local
RUN ldconfig
WORKDIR /app
COPY --from=server-builder /app/build/linux/x64/release/bundle ./bundle
COPY --from=server-builder /app/ffi/libimage_magick_ffi.so ./bundle
   
# You can also make this docker image act as if it were running in GCP
# So you can use all the Google Cloud libraries in a dev environment
# But only add this if your in a dev environment as GCP automatically
# Adds these to the environment. 
### DEV ONLY NOT FOR GCP ###################################################
COPY my-gcp-svc-acct-key.json ./ 
ENV GOOGLE_APPLICATION_CREDENTIALS=/app/my-gcp-svc-acct-key.json
ENV GCP_PROJECT=my-gcp-project-id
############################################################################
   
# Link libraries to LD path so they are visible on linux
ENV LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib:/usr/lib:
   
# Find the server executable
RUN find ./bundle -type f -executable ! -name "*.so" -printf "%f\n" > executable_name.txt
EXPOSE 8080
   
# Run the flutter server with xvfb to simulate a display
CMD xvfb-run -a ./bundle/$(cat executable_name.txt)

ostrich

Benefits

Setup (Docker)

Setup (Docker with ImageMagick via FFI)

Libraries

ostrich package