The only changes needed to get this working in k8s + Tilt

rails-example/Containerfile.dev

@@ -0,0 +1,47 @@
+# syntax = docker/dockerfile:1
+
+# Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
+ARG RUBY_VERSION=3.3.0
+FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
+
+# Rails app lives here
+WORKDIR /rails
+
+# Set development environment
+ENV RAILS_ENV="development" \
+    BUNDLE_PATH="/usr/local/bundle"
+
+# Install packages needed to build gems and node modules
+RUN apt-get update -qq && \
+    apt-get install --no-install-recommends -y build-essential curl git libpq-dev libvips node-gyp pkg-config python-is-python3
+
+# Install JavaScript dependencies
+ARG NODE_VERSION=20.10.0
+ARG YARN_VERSION=1.22.19
+ENV PATH=/usr/local/node/bin:$PATH
+RUN curl -sL https://github.com/nodenv/node-build/archive/master.tar.gz | tar xz -C /tmp/ && \
+    /tmp/node-build-master/bin/node-build "${NODE_VERSION}" /usr/local/node && \
+    npm install -g yarn@$YARN_VERSION && \
+    rm -rf /tmp/node-build-master
+
+# Install application gems
+COPY Gemfile Gemfile.lock ./
+RUN bundle install
+
+# Install node modules
+COPY package.json yarn.lock ./
+RUN yarn install
+
+# Copy application code
+COPY . .
+
+# Build assets in dev mode
+RUN yarn build
+RUN yarn build:css
+
+# Entrypoint prepares the database.
+ENTRYPOINT ["/rails/bin/docker-entrypoint"]
+
+# Start the server by default, this can be overwritten at runtime
+EXPOSE 3000
+CMD ["./bin/rails", "server"]

rails-example/Tiltfile

@@ -0,0 +1,55 @@
+load('ext://helm_resource', 'helm_resource', 'helm_repo')
+load('ext://podman', 'podman_build')
+load('ext://secret', 'secret_from_dict')
+load('ext://uibutton', 'cmd_button')
+
+# Set up secrets with defaults for development
+k8s_yaml(secret_from_dict('tiltfile', inputs = {
+  'postgres-password' : os.getenv('POSTGRESQL_PASSWORD', 's3sam3')
+}))
+
+# Use Helm to spin up postgres
+helm_resource(
+  name='postgresql',
+  chart='oci://registry-1.docker.io/bitnamicharts/postgresql',
+  flags=[
+      # TODO: 15.x appears to have problems with ephemeral-storage limits that
+      # I haven't been able to debug yet
+      '--version=^14.0',
+      '--set=image.tag=16.2.0-debian-12-r8',
+      '--set=global.postgresql.auth.existingSecret=tiltfile'
+  ],
+  labels=['database']
+)
+
+# The Rails app itself is built and served by app.yaml
+podman_build('rails-example', '.', 
+  extra_flags=['--file', 'Containerfile.dev'],
+  live_update=[
+    fall_back_on(['./config']),
+    sync('.', '/rails'),
+    run('bundle', trigger=['./Gemfile', './Gemfile.lock']),
+    run('yarn', trigger=['./package.json', './yarn.lock']),
+    run('yarn build', trigger=['./app/javascript']),
+    run('yarn build:css', trigger=['./app/assets/stylesheets']),
+  ]
+)
+k8s_yaml('k8s.yaml')
+k8s_resource('rails-example', 
+  labels=['app'],
+  resource_deps=['postgresql'],
+  port_forwards='3000:3000'
+)
+cmd_button('rails-example:db-migrate',
+  argv=['./bin/tilt-run', 'rails', 'db:migrate'],
+  resource='rails-example',
+  icon_name='engineering',
+  text='Run migrations',
+)
+cmd_button('rails-example:db-reset',
+  argv=['./bin/tilt-run', 'rails', 'db:seed:replant'],
+  resource='rails-example',
+  icon_name='restart_alt',
+  text='Reset database',
+  requires_confirmation=True,
+)

rails-example/bin/tilt-run

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+RESOURCE=rails-example
+POD_NAME="$(tilt get kubernetesdiscovery "$RESOURCE" -ojsonpath='{.status.pods[0].name}')"
+# If we're running this from a terminal, attach a terminal here too
+if [ -t 0 ]; then FLAGS="-ti"; fi
+kubectl exec $FLAGS "$POD_NAME" -- bundle exec $@

rails-example/config/database.yml

@@ -18,6 +18,9 @@ default: &default
   # For details on connection pooling, see Rails configuration guide
   # https://guides.rubyonrails.org/configuring.html#database-pooling
   pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+  host: <%= ENV.fetch("POSTGRESQL_SERVICE_HOST", nil) %>
+  username: postgres
+  password: <%= ENV.fetch("POSTGRES_PASSWORD", nil) %>
 
 development:
   <<: *default

rails-example/k8s.yaml

@@ -0,0 +1,26 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: rails-example
+  labels:
+    app: rails-example
+spec:
+  selector:
+    matchLabels:
+      app: rails-example
+  template:
+    metadata:
+      labels:
+        app: rails-example
+    spec:
+      containers:
+        - name: rails-example
+          image: rails-example
+          ports:
+            - containerPort: 3000
+          env:
+            - name: POSTGRES_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: tiltfile
+                  key: postgres-password