Open-Source DevOps · seuros

capistrano-puma

Capistrano-Puma is a Ruby gem that automates Puma web server deployment and lifecycle management via Capistrano, using systemd for service control. It handles zero-downtime deployments, socket activation, and systemd service installation for Rails applications.

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Source: GitHub — github.com/seuros/capistrano-puma

623

GitHub stars

301

Forks

Ruby

Primary language

MIT

License (OSI-approved)

Key facts

Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.

Field	Value
Repository	seuros/capistrano-puma
Owner	seuros
Primary language	Ruby
License	MIT — OSI-approved
Stars	623
Forks	301
Open issues	0
Latest release	Unknown
Last updated	2026-06-21
Source	https://github.com/seuros/capistrano-puma

What capistrano-puma is

A Capistrano plugin providing systemd-based Puma service management, supporting Puma 5.1+, socket activation, phased restarts, and configurable bind addresses (TCP or Unix socket). Version 6.0+ requires manual puma.rb configuration and user-level systemd services.

Quickstart

Get the capistrano-puma source

Clone the repository and explore it locally.

terminalbash

1git clone https://github.com/seuros/capistrano-puma.git2cd capistrano-puma3# follow the project's README for install & configuration

Need it deployed, integrated, or customized instead? DEV.co ships production installs.

Best use cases

Rails app deployments with zero-downtime restarts

Automates graceful Puma restarts via systemd, enabling phased reloads without dropping requests—ideal for production Rails workloads requiring high availability.

Capistrano-based deployment pipelines

Integrates directly into Capistrano workflows; provides cap tasks for install, start, stop, restart, and status, reducing manual systemd service configuration.

Multi-instance or socket-activated deployments

Supports systemd socket activation (start-on-demand) and configurable bind addresses, useful for resource-constrained or containerized Ruby environments.

Implementation considerations

Must run `cap <stage> puma:install` once per server before first deployment—gem does not auto-install systemd service, and deployment will succeed but Puma won't start.
Version 6.0+ breaking change: manually create `config/puma.rb` in repository and add to linked_files; gem no longer auto-generates it.
Explicitly set `puma_bind` (e.g., `unix://#{shared_path}/tmp/sockets/puma.sock`); no default bind address in v6.0+.
Systemd services are user-scoped by default (`~/.config/systemd/user/`); ensure deployment user has permission to manage user services.
Nginx upstream configuration must match puma_bind setting (socket vs. TCP port) to avoid 502 errors.

When to avoid it — and what to weigh

Not using Capistrano for deployment — This gem is tightly coupled to Capistrano; other deploy tools (Kubernetes, Docker Compose, manual systemd) require different solutions.
Puma version < 5.1 — Gem explicitly targets Puma 5.1+; older versions lack required systemd integration features.
Non-systemd Linux environments or non-Linux OS — Gem relies on systemd for service management; Windows, macOS, or init-based systems require manual workarounds or alternative tools.
Kubernetes or container orchestration deployments — systemd service management is anti-pattern in Kubernetes; container runtimes handle process lifecycle differently.

License & commercial use

MIT License—permissive OSI-approved license allowing commercial use, modification, and distribution with attribution.

MIT is a permissive open-source license that explicitly permits commercial use. No license restrictions apply to deploying this gem in production. However, verify your deployment infrastructure's license compliance separately (e.g., Capistrano, Puma, Ruby runtime).

DEV.co evaluation signals

Editorial assessment — not user reviews. Directional, with an explicit confidence level.

Signal	Assessment
Maintenance	Active
Documentation	Strong
License clarity	Clear
Deployment complexity	Moderate
DEV.co fit	Good
Assessment confidence	High

Security considerations

Systemd services run under specified user (default: deploy user); ensure user cannot escalate privileges. Unix socket binding is more secure than TCP 0.0.0.0; verify file permissions on shared socket directories. No security audit or CVE data provided. Puma security posture depends on Puma and Ruby runtime versions (outside scope of this gem).

Alternatives to consider

mina gem

Lightweight Capistrano alternative with simpler syntax; lacks built-in systemd service management, requires manual systemd or init scripts.

Kubernetes/Helm + container deployment

Container orchestration handles Puma lifecycle natively; no gem needed. Overkill for small/mid-scale apps but superior for multi-instance scaling and HA.

Phusion Passenger

Alternative app server with built-in Nginx integration and auto-restarts; eliminates separate process manager but ties you to Passenger's deployment model.

Software development agency

Build on capistrano-puma with DEV.co software developers

Integrate Capistrano-Puma to automate Puma lifecycle management and enable zero-downtime restarts. Review the setup guide and example app to get started.

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capistrano-puma FAQ

Why does my deployment succeed but Puma doesn't start?

You likely skipped the one-time `cap <stage> puma:install` command. This gem does not auto-create systemd services; run it before your first deploy.

What changed in version 6.0?

Three breaking changes: (1) puma.rb is no longer auto-generated—you must create it and add to linked_files, (2) puma_bind now requires explicit configuration, (3) systemd services are user-scoped (~/.config/systemd/user/) instead of system-wide.

Can I use this with Docker or Kubernetes?

Not recommended. systemd is a Linux host init system; container runtimes (Docker, Kubernetes) manage process lifecycle differently. Use container-native deployment or alternative tools instead.

Does this support zero-downtime deployments?

Yes. Systemd phased restarts allow Puma to reload gracefully, spawning new workers before terminating old ones, and the gem exposes smart_restart and reload tasks for this purpose.

Work with a software development agency

Adopting capistrano-puma is usually one piece of a larger software development effort. As a software development agency, DEV.co provides software development services and web development expertise — pairing senior software developers and web developers with your team to design, build, and operate open-source devops software in production.

Ready to streamline your Rails deployments?

Integrate Capistrano-Puma to automate Puma lifecycle management and enable zero-downtime restarts. Review the setup guide and example app to get started.

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