Allow using env var to specify pidfile

guides/source/initialization.md

@@ -289,7 +289,7 @@ def default_options
     environment:        (ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "development").dup,
     daemonize:          false,
     caching:            nil,
-    pid:                Options::DEFAULT_PID_PATH,
+    pid:                ENV.fetch("PIDFILE", Options::DEFAULT_PIDFILE).dup,
     restart_cmd:        restart_command)
 end
 ```

railties/CHANGELOG.md

@@ -1,3 +1,5 @@
+* Support using environment variable to set pidfile
 
+  *Ben Thorner*
 
 Please check [6-0-stable](https://github.com/rails/rails/blob/6-0-stable/railties/CHANGELOG.md) for previous changes.

railties/lib/rails/commands/server/server_command.rb

@@ -99,7 +99,7 @@ class ServerCommand < Base # :nodoc:
       RACK_SERVERS = %w(cgi fastcgi webrick lsws scgi thin puma unicorn)
 
       DEFAULT_PORT = 3000
-      DEFAULT_PID_PATH = "tmp/pids/server.pid"
+      DEFAULT_PIDFILE = "tmp/pids/server.pid"
 
       argument :using, optional: true
 
@@ -114,8 +114,8 @@ class ServerCommand < Base # :nodoc:
         desc: "Runs server as a Daemon."
       class_option :using, aliases: "-u", type: :string,
         desc: "Specifies the Rack server used to run the application (thin/puma/webrick).", banner: :name
-      class_option :pid, aliases: "-P", type: :string, default: DEFAULT_PID_PATH,
-        desc: "Specifies the PID file."
+      class_option :pid, aliases: "-P", type: :string,
+        desc: "Specifies the PID file - defaults to #{DEFAULT_PIDFILE}."
       class_option :dev_caching, aliases: "-C", type: :boolean, default: nil,
         desc: "Specifies whether to perform caching in development."
       class_option :restart, type: :boolean, default: nil, hide: true
@@ -207,6 +207,7 @@ def user_supplied_options
             end
             user_supplied_options << :Host if ENV["HOST"] || ENV["BINDING"]
             user_supplied_options << :Port if ENV["PORT"]
+            user_supplied_options << :pid if ENV["PIDFILE"]
             user_supplied_options.uniq
           end
         end
@@ -253,15 +254,15 @@ def log_to_stdout?
         end
 
         def pid
-          File.expand_path(options[:pid])
+          File.expand_path(options[:pid] || ENV.fetch("PIDFILE", DEFAULT_PIDFILE))
         end
 
         def self.banner(*)
           "rails server -u [thin/puma/webrick] [options]"
         end
 
         def prepare_restart
-          FileUtils.rm_f(options[:pid]) if options[:restart]
+          FileUtils.rm_f(pid) if options[:restart]
         end
 
         def deprecate_positional_rack_server_and_rewrite_to_option(original_options)

railties/test/commands/server_test.rb

@@ -116,6 +116,13 @@ def test_environment_with_binding
     end
   end
 
+  def test_environment_with_pidfile
+    switch_env "PIDFILE", "/tmp/rails.pid" do
+      options = parse_arguments
+      assert_equal "/tmp/rails.pid", options[:pid]
+    end
+  end
+
   def test_caching_without_option
     args = []
     options = parse_arguments(args)
@@ -234,6 +241,12 @@ def test_argument_precedence_over_environment_variable
       options = parse_arguments(args)
       assert_equal "127.0.0.1", options[:Host]
     end
+
+    switch_env "PIDFILE", "/tmp/rails.pid" do
+      args = ["-P", "/somewhere/else.pid"]
+      options = parse_arguments(args)
+      assert_equal "/somewhere/else.pid", options[:pid]
+    end
   end
 
   def test_records_user_supplied_options
@@ -253,6 +266,16 @@ def test_records_user_supplied_options
       server_options = parse_arguments
       assert_equal [:Host], server_options[:user_supplied_options]
     end
+
+    switch_env "PORT", "3001" do
+      server_options = parse_arguments
+      assert_equal [:Port], server_options[:user_supplied_options]
+    end
+
+    switch_env "PIDFILE", "/tmp/server.pid" do
+      server_options = parse_arguments
+      assert_equal [:pid], server_options[:user_supplied_options]
+    end
   end
 
   def test_default_options