Make systemd unit configurable and fix :system-mode defaults

- Add :solid_queue_service_unit_env_files / :solid_queue_service_unit_env_vars
  for injecting EnvironmentFile= and Environment="KEY=VALUE" lines into the
  unit (inspired by capistrano-sidekiq). Both fall back to shared
  :service_unit_env_files / :service_unit_env_vars.
- Add :solid_queue_command (default "rake solid_queue:start") so setups on
  SolidQueue >= 0.4 can switch to "bin/jobs" without templating.
- Fix WantedBy: multi-user.target when running in :system mode (previously
  always default.target, which prevented boot activation of system units).
- Fix :system mode running the service implicitly as root — now uses
  :solid_queue_user (falls back to :run_as, then :user).
- Drop implicit rendering of Capistrano's default_env and the hardcoded
  MALLOC_ARENA_MAX=2; pass anything you need explicitly via the new hooks.
  RAILS_ENV is still derived from the current stage.

Author: floriancrusius

CHANGELOG.md

@@ -1,5 +1,22 @@
 ## [Unreleased]
 
+- Make systemd unit environment variables configurable via
+  `:solid_queue_service_unit_env_files` and `:solid_queue_service_unit_env_vars`
+  (inspired by `capistrano-sidekiq`). Both fall back to shared
+  `:service_unit_env_files` / `:service_unit_env_vars` when set.
+- Make the executed command configurable via `:solid_queue_command`
+  (default: `"rake solid_queue:start"`) so SolidQueue >= 0.4 setups can use
+  `"bin/jobs"`.
+- Fix: `[Install] WantedBy=` now switches to `multi-user.target` when running
+  in `:system` mode (previously always `default.target`, which prevented boot
+  activation of system units).
+- Fix: in `:system` mode the service now runs as `:solid_queue_user`
+  (defaults to `:run_as` → `:user`) instead of implicitly running as root.
+- **Breaking**: Capistrano's `default_env` is no longer rendered into the
+  systemd unit file. `MALLOC_ARENA_MAX=2` is no longer hardcoded either. Pass
+  what you need explicitly via the new configuration hooks. `RAILS_ENV` is
+  still set from the current stage.
+
 ## [0.1.2] - 2025-06-12
 
 - Quiet task only runs on :solid_queue_role [#3](https://github.com/codeur/capistrano-solid_queue/pull/5) by [@bashcoder](https://github.com/bashcoder)

README.md

@@ -70,6 +70,56 @@ through their Capistrano counterparts, ex: `bundle exec cap solid_queue:restart`
 The plugin has registered a Capistrano `hook` to run `bundle exec cap solid_queue:restart` after deploy.
 See [`#register_hooks`](lib/capistrano/solid_queue.rb)
 
+## Configuration
+
+The following variables can be set in your `deploy.rb` or stage files:
+
+```ruby
+set :solid_queue_role, :app
+set :solid_queue_access_log, -> { File.join(shared_path, "log", "solid_queue.log") }
+set :solid_queue_error_log,  -> { File.join(shared_path, "log", "solid_queue.log") }
+set :solid_queue_service_unit_name, -> { "#{fetch(:application)}_solid_queue_#{fetch(:stage)}" }
+set :solid_queue_systemctl_user, :user # or :system
+
+# What runs after `bundle exec` — override for SolidQueue >= 0.4:
+set :solid_queue_command, "bin/jobs"
+
+# Unix user for the service when running in :system mode
+# (defaults to :run_as, then to Capistrano's :user)
+set :solid_queue_user, "deploy"
+```
+
+### Environment variables
+
+Two hooks let you inject arbitrary environment into the generated systemd unit
+(inspired by [`capistrano-sidekiq`](https://github.com/seuros/capistrano-sidekiq)):
+
+```ruby
+# Referenced via `EnvironmentFile=` — one line per file
+set :solid_queue_service_unit_env_files, %w[
+  /etc/environment
+  /home/deploy/apps/my_app/shared/.env
+]
+
+# Rendered as `Environment="KEY=VALUE"` — one line per entry
+set :solid_queue_service_unit_env_vars, [
+  "RAILS_LOG_TO_STDOUT=1",
+  "DB_POOL=10",
+  "SOLID_QUEUE_IN_PUMA=false"
+]
+```
+
+If your project already sets `:service_unit_env_files` / `:service_unit_env_vars`
+(shared with other systemd-based capistrano plugins), they are picked up as
+the default — you only need to override when SolidQueue should see a different
+set of variables.
+
+Only `RAILS_ENV=<stage>` is set implicitly (it is derived directly from the
+Capistrano stage). Capistrano's `default_env` is **not** rendered into the unit
+file — pass anything else you need (including tuning knobs like
+`MALLOC_ARENA_MAX`) via `:solid_queue_service_unit_env_vars` or
+`:solid_queue_service_unit_env_files`.
+
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

lib/capistrano/solid_queue.rb

@@ -11,6 +11,19 @@ def set_defaults
         set_if_empty :solid_queue_error_log, -> { File.join(shared_path, "log", "solid_queue.log") }
         set_if_empty :solid_queue_service_unit_name, -> { "#{fetch(:application)}_solid_queue_#{fetch(:stage)}" }
         set_if_empty :solid_queue_systemd_conf_dir, -> { fetch_systemd_unit_path }
+
+        # Command executed by the systemd unit (concatenated after `bundle exec`).
+        # Override with e.g. "bin/jobs" for SolidQueue >= 0.4 setups.
+        set_if_empty :solid_queue_command, "rake solid_queue:start"
+
+        # Unix user the service runs as when using `:system` mode. Falls back to
+        # `:run_as` (shared with other systemd capistrano plugins) and finally
+        # the SSH `:user` capistrano connects with.
+        set_if_empty :solid_queue_user, -> { fetch(:run_as, fetch(:user)) }
+
+        # SolidQueue could have a stripped down or more complex version of the environment variables
+        set_if_empty :solid_queue_service_unit_env_files, -> { fetch(:service_unit_env_files, []) }
+        set_if_empty :solid_queue_service_unit_env_vars, -> { fetch(:service_unit_env_vars, []) }
       end
 
       def define_tasks

lib/capistrano/templates/solid_queue.service.erb

@@ -1,18 +1,21 @@
 [Unit]
-Description=SolidQueue background job
+Description=SolidQueue background job for <%= "#{fetch(:application)} (#{fetch(:stage)})" %>
 After=syslog.target network.target
 
 [Service]
 Type=simple
-Environment='RAILS_ENV=<%= fetch(:stage) %>'
-<% fetch(:default_env).reject{ |k, _| k.to_s == 'path' }.each do |variable, value| -%>
-Environment='<%= variable.to_s.upcase %>=<%= value.to_s %>'
+<%= "User=#{fetch(:solid_queue_user)}" if fetch(:solid_queue_systemctl_user) == :system %>
+Environment=RAILS_ENV=<%= fetch(:stage) %>
+<% Array(fetch(:solid_queue_service_unit_env_files)).each do |file| -%>
+EnvironmentFile=<%= file %>
+<% end -%>
+<% Array(fetch(:solid_queue_service_unit_env_vars)).each do |environment_variable| -%>
+Environment="<%= environment_variable %>"
 <% end -%>
 WorkingDirectory=<%= current_path %>
-ExecStart=<%= capture(:echo, SSHKit.config.command_map[:bundle]).strip %> exec rake solid_queue:start
+ExecStart=<%= capture(:echo, SSHKit.config.command_map[:bundle]).strip %> exec <%= fetch(:solid_queue_command) %>
 ExecReload=/bin/kill -TSTP $MAINPID
 ExecStop=/bin/kill -TERM $MAINPID
-Environment=MALLOC_ARENA_MAX=2
 
 # if we crash, restart
 RestartSec=1
@@ -24,4 +27,4 @@ Restart=on-failure
 SyslogIdentifier=<%= fetch(:solid_queue_service_unit_name) %>
 
 [Install]
-WantedBy=default.target
+WantedBy=<%= fetch(:solid_queue_systemctl_user) == :system ? "multi-user.target" : "default.target" %>