Add built-in systemd notify support (#3011)

Gemfile

@@ -10,7 +10,6 @@ gem "minitest", "~> 5.11"
 gem "minitest-retry"
 gem "minitest-proveit"
 gem "minitest-stub-const"
-gem "sd_notify"
 
 gem "rack", (ENV['PUMA_CI_RACK_2'] ? "~> 2.2" : ">= 2.2")
 

docs/systemd.md

@@ -24,8 +24,7 @@ After=network.target
 
 [Service]
 # Puma supports systemd's `Type=notify` and watchdog service
-# monitoring, if the [sd_notify](https://github.com/agis/ruby-sdnotify) gem is installed,
-# as of Puma 5.1 or later.
+# monitoring, as of Puma 5.1 or later.
 # On earlier versions of Puma or JRuby, change this to `Type=simple` and remove
 # the `WatchdogSec` line.
 Type=notify

lib/puma/launcher.rb

@@ -318,12 +318,7 @@ def reload_worker_directory
     def integrate_with_systemd
       return unless ENV["NOTIFY_SOCKET"]
 
-      begin
-        require_relative 'systemd'
-      rescue LoadError
-        log "Systemd integration failed. It looks like you're trying to use systemd notify but don't have sd_notify gem installed"
-        return
-      end
+      require_relative 'systemd'
 
       log "* Enabling systemd notification integration"
 

lib/puma/sd_notify.rb

@@ -0,0 +1,149 @@
+# frozen_string_literal: true
+
+require "socket"
+
+module Puma
+  # The MIT License
+  #
+  # Copyright (c) 2017-2022 Agis Anastasopoulos
+  #
+  # Permission is hereby granted, free of charge, to any person obtaining a copy of
+  # this software and associated documentation files (the "Software"), to deal in
+  # the Software without restriction, including without limitation the rights to
+  # use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+  # the Software, and to permit persons to whom the Software is furnished to do so,
+  # subject to the following conditions:
+  #
+  # The above copyright notice and this permission notice shall be included in all
+  # copies or substantial portions of the Software.
+  #
+  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+  # FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+  # COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+  # IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+  # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+  #
+  # This is a copy of https://github.com/agis/ruby-sdnotify as of commit cca575c
+  # The only changes made was "rehoming" it within the Puma module to avoid
+  # namespace collisions and applying standard's code formatting style.
+  #
+  # SdNotify is a pure-Ruby implementation of sd_notify(3). It can be used to
+  # notify systemd about state changes. Methods of this package are no-op on
+  # non-systemd systems (eg. Darwin).
+  #
+  # The API maps closely to the original implementation of sd_notify(3),
+  # therefore be sure to check the official man pages prior to using SdNotify.
+  #
+  # @see https://www.freedesktop.org/software/systemd/man/sd_notify.html
+  module SdNotify
+    # Exception raised when there's an error writing to the notification socket
+    class NotifyError < RuntimeError; end
+
+    READY     = "READY=1"
+    RELOADING = "RELOADING=1"
+    STOPPING  = "STOPPING=1"
+    STATUS    = "STATUS="
+    ERRNO     = "ERRNO="
+    MAINPID   = "MAINPID="
+    WATCHDOG  = "WATCHDOG=1"
+    FDSTORE   = "FDSTORE=1"
+
+    def self.ready(unset_env=false)
+      notify(READY, unset_env)
+    end
+
+    def self.reloading(unset_env=false)
+      notify(RELOADING, unset_env)
+    end
+
+    def self.stopping(unset_env=false)
+      notify(STOPPING, unset_env)
+    end
+
+    # @param status [String] a custom status string that describes the current
+    #   state of the service
+    def self.status(status, unset_env=false)
+      notify("#{STATUS}#{status}", unset_env)
+    end
+
+    # @param errno [Integer]
+    def self.errno(errno, unset_env=false)
+      notify("#{ERRNO}#{errno}", unset_env)
+    end
+
+    # @param pid [Integer]
+    def self.mainpid(pid, unset_env=false)
+      notify("#{MAINPID}#{pid}", unset_env)
+    end
+
+    def self.watchdog(unset_env=false)
+      notify(WATCHDOG, unset_env)
+    end
+
+    def self.fdstore(unset_env=false)
+      notify(FDSTORE, unset_env)
+    end
+
+    # @param [Boolean] true if the service manager expects watchdog keep-alive
+    #   notification messages to be sent from this process.
+    #
+    # If the $WATCHDOG_USEC environment variable is set,
+    # and the $WATCHDOG_PID variable is unset or set to the PID of the current
+    # process
+    #
+    # @note Unlike sd_watchdog_enabled(3), this method does not mutate the
+    #   environment.
+    def self.watchdog?
+      wd_usec = ENV["WATCHDOG_USEC"]
+      wd_pid = ENV["WATCHDOG_PID"]
+
+      return false if !wd_usec
+
+      begin
+        wd_usec = Integer(wd_usec)
+      rescue
+        return false
+      end
+
+      return false if wd_usec <= 0
+      return true if !wd_pid || wd_pid == $$.to_s
+
+      false
+    end
+
+    # Notify systemd with the provided state, via the notification socket, if
+    # any.
+    #
+    # Generally this method will be used indirectly through the other methods
+    # of the library.
+    #
+    # @param state [String]
+    # @param unset_env [Boolean]
+    #
+    # @return [Fixnum, nil] the number of bytes written to the notification
+    #   socket or nil if there was no socket to report to (eg. the program wasn't
+    #   started by systemd)
+    #
+    # @raise [NotifyError] if there was an error communicating with the systemd
+    #   socket
+    #
+    # @see https://www.freedesktop.org/software/systemd/man/sd_notify.html
+    def self.notify(state, unset_env=false)
+      sock = ENV["NOTIFY_SOCKET"]
+
+      return nil if !sock
+
+      ENV.delete("NOTIFY_SOCKET") if unset_env
+
+      begin
+        Addrinfo.unix(sock, :DGRAM).connect do |s|
+          s.close_on_exec = true
+          s.write(state)
+        end
+      rescue StandardError => e
+        raise NotifyError, "#{e.class}: #{e.message}", e.backtrace
+      end
+    end
+  end
+end

lib/puma/systemd.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'sd_notify'
+require_relative 'sd_notify'
 
 module Puma
   class Systemd

test/test_integration_systemd.rb

@@ -1,8 +1,6 @@
 require_relative "helper"
 require_relative "helpers/integration"
 
-require 'sd_notify'
-
 class TestIntegrationSystemd < TestIntegration
   def setup
     skip "Skipped because Systemd support is linux-only" if windows? || osx?