Deploying Ruby, the language.: what should I watch out for? (#1)

Don't ship a Gemfile.lock built on macOS ARM to a Linux x86 container — bundler platform mismatches will haunt you. Run `bundle lock --add-platform x86_64-linux`.

Deploying Ruby, the language.: what should I watch out for? (#2)

Signal handling: production containers get SIGTERM. Trap it and drain in-flight work, or your job queue will orphan messages.

Deploying Ruby, the language.: what should I watch out for? (#3)

Time zones. Set `TZ=UTC` at the container level and rely on ActiveSupport / Time.iso8601. Debugging tz drift in cron is a special hell.

// framework · ruby

Ruby, the language.

Before Rails there was Ruby. Here's how to ship the runtime itself — workers, CLIs, and small services — onto real infrastructure.

Not every Ruby workload is a Rails monolith. Data pipelines, ETL scripts, chatops bots and background workers all deserve a first-class deployment story. This guide covers Ruby 3.3+ with YJIT, memory allocator picks, and container images that stay under 200 MB.

112 MB

min container size

1.7×

YJIT speedup

480 ms

cold start (Cloud Run)

01 / 04

Pick a base image

Use the slim official image and add only what you need. Alpine works but musl vs glibc bugs will find you eventually — start with Debian slim and only optimize if the size matters.

Dockerfile
FROM ruby:3.3-slim AS build
RUN apt-get update -qq && apt-get install -y build-essential git
WORKDIR /app
COPY Gemfile Gemfile.lock ./
RUN bundle config set --local deployment 'true' \
 && bundle config set --local without 'development test' \
 && bundle install --jobs 4

FROM ruby:3.3-slim
WORKDIR /app
COPY --from=build /usr/local/bundle /usr/local/bundle
COPY . .
ENV RUBY_YJIT_ENABLE=1 MALLOC_ARENA_MAX=2
CMD ["ruby", "bin/worker"]

02 / 04

Turn on YJIT

Ruby 3.3's YJIT is stable and boring — the best kind of feature. Enable it with the env var above. Expect a ~1.5–2× throughput bump on real code with almost no memory penalty.

03 / 04

Tame memory

Set MALLOC_ARENA_MAX=2 to stop glibc from ballooning RSS on multi-threaded processes. On AWS Fargate or Cloud Run this alone often halves resident memory and keeps you well inside a 512 MB container.

04 / 04

Structured logs to stdout

Every cloud logger — CloudWatch, Cloud Logging, Log Analytics, Papertrail — assumes you write JSON to stdout. Use a lean logger and never touch the filesystem for logs.

ruby
require "json"
require "logger"

logger = Logger.new($stdout)
logger.formatter = ->(sev, time, _prog, msg) {
  JSON.generate(t: time.iso8601, l: sev, m: msg) + "\n"
}
logger.info("worker.boot", pid: Process.pid)

Gotchas we learned the hard way

!Don't ship a Gemfile.lock built on macOS ARM to a Linux x86 container — bundler platform mismatches will haunt you. Run `bundle lock --add-platform x86_64-linux`.
!Signal handling: production containers get SIGTERM. Trap it and drain in-flight work, or your job queue will orphan messages.
!Time zones. Set `TZ=UTC` at the container level and rely on ActiveSupport / Time.iso8601. Debugging tz drift in cron is a special hell.