[PATCH] allow omitting specifying socket name when inheriting listen socket

[Eric Wong <e@80x24.org>]

Since the common case is still to run a single app inside yahns,
we can simplify setup a bit for systemd (and like) users by
allowing them to omit the "listen" directive when they are
running a single app in yahns.
---
 Documentation/yahns-rackup.pod |  4 ++++
 lib/yahns/config.rb            |  5 +++++
 lib/yahns/rackup_handler.rb    |  6 +++---
 lib/yahns/server.rb            |  4 +++-
 test/test_bin.rb               | 47 +++++++++++++++++++++---------------------
 5 files changed, 39 insertions(+), 27 deletions(-)

diff --git a/Documentation/yahns-rackup.pod b/Documentation/yahns-rackup.pod
index 3fbde0e..de2d4b6 100644
--- a/Documentation/yahns-rackup.pod
+++ b/Documentation/yahns-rackup.pod
@@ -40,6 +40,10 @@ and PATH is meant to be a path to a UNIX domain socket.
 Defaults to "0.0.0.0:9292" (all addresses on TCP port 9292).
 Multiple addresses may be separated with commas.
 
+For systemd users, a special value of "inherit" may be specified
+to inherit FDs using the LISTEN_FDS and LISTEN_PID environment
+variables described in L<sd_listen_fds(3)>
+
 =item -O stderr_path=PATHNAME
 
 Allow redirecting $stderr to a given path.  Unlike doing this from
diff --git a/lib/yahns/config.rb b/lib/yahns/config.rb
index e545d59..bcea0d4 100644
--- a/lib/yahns/config.rb
+++ b/lib/yahns/config.rb
@@ -438,4 +438,9 @@ def commit!(server)
 
     @app_ctx.each { |app| app.logger ||= server.logger }
   end
+
+  def register_inherited(name)
+    return unless @config_listeners.empty? && @app_ctx.size == 1
+    @config_listeners[name] = { :yahns_app_ctx => @app_ctx[0] }
+  end
 end
diff --git a/lib/yahns/rackup_handler.rb b/lib/yahns/rackup_handler.rb
index 63ab373..3f217af 100644
--- a/lib/yahns/rackup_handler.rb
+++ b/lib/yahns/rackup_handler.rb
@@ -16,10 +16,10 @@ def self.run(app, o)
       # fine for most apps, but we have SIGUSR2 restarts to support
       working_directory(Yahns::START[:cwd])
 
-      app(:rack, app) do
+      app(:rack, app) do # Yahns::Config#app
         addr = o[:listen] || "#{o[:Host]||default_host}:#{o[:Port]||8080}"
-        # allow listening to multiple addresses
-        addr.split(',').each { |l| listen(l) }
+        # allow listening to multiple addresses (Yahns::Config#listen)
+        addr.split(',').each { |l| listen(l) } unless addr == 'inherit'
 
         val = o[:client_timeout] and client_timeout(val)
       end
diff --git a/lib/yahns/server.rb b/lib/yahns/server.rb
index 43caae6..efd6f05 100644
--- a/lib/yahns/server.rb
+++ b/lib/yahns/server.rb
@@ -327,7 +327,9 @@ def inherit_listeners!
       opts = sock_opts(io)
       io = server_cast(io, opts)
       set_server_sockopt(io, opts)
-      @logger.info "inherited addr=#{sock_name(io)} fd=#{io.fileno}"
+      name = sock_name(io)
+      @logger.info "inherited addr=#{name} fd=#{io.fileno}"
+      @config.register_inherited(name)
       io
     end
 
diff --git a/test/test_bin.rb b/test/test_bin.rb
index 579e39c..e59c9b4 100644
--- a/test/test_bin.rb
+++ b/test/test_bin.rb
@@ -14,35 +14,36 @@ def setup
 
   def test_listen_fd3
     return unless RUBY_VERSION.to_f > 2.3 # Fixed in ruby/trunk r51209, actually
-    @srv.setsockopt(:SOL_SOCKET, :SO_KEEPALIVE, 0)
     host, port = @srv.addr[3], @srv.addr[1]
 
     ru = tmpfile(%w(test_bin_daemon .ru))
     ru.write("require 'rack/lobster'; run Rack::Lobster.new\n")
-    cmd = %W(#{RbConfig.ruby} -I lib bin/yahns-rackup
-             -E none -p #{port} -o #{host} #{ru.path})
-    pid = fork do # emulate a systemd environment
-      env = {
-        'LISTEN_PID' => $$.to_s,
-        'LISTEN_FDS' => '1',
-      }
-      exec env, *cmd, 3 => @srv, err: @err.path
-    end
-    Net::HTTP.start(host, port) do |http|
-      req = Net::HTTP::Get.new("/")
-      res = http.request(req)
-      assert_equal 200, res.code.to_i
-      assert_equal "keep-alive", res["Connection"]
+    cmd = %W(#{RbConfig.ruby} -I lib bin/yahns-rackup -E none #{ru.path})
+    [ %w(-O listen=inherit), %W(-p #{port} -o #{host}) ].each do |opt|
+      @srv.setsockopt(:SOL_SOCKET, :SO_KEEPALIVE, 0)
+      begin
+        pid = fork do # emulate a systemd environment
+          env = { 'LISTEN_PID' => $$.to_s, 'LISTEN_FDS' => '1' }
+          cmd.concat(opt)
+          exec env, *cmd, 3 => @srv, err: @err.path
+        end
+        Net::HTTP.start(host, port) do |http|
+          req = Net::HTTP::Get.new("/")
+          res = http.request(req)
+          assert_equal 200, res.code.to_i
+          assert_equal "keep-alive", res["Connection"]
+        end
+        assert @srv.getsockopt(:SOL_SOCKET, :SO_KEEPALIVE).bool,
+                     'ensure the inheriting process applies TCP socket options'
+      ensure
+        if pid
+          Process.kill(:QUIT, pid)
+          _, status = Process.waitpid2(pid)
+          assert status.success?, status.inspect
+        end
+      end
     end
-
-    assert @srv.getsockopt(:SOL_SOCKET, :SO_KEEPALIVE).bool,
-                 'ensure the inheriting process applies TCP socket options'
   ensure
-    if pid
-      Process.kill(:QUIT, pid)
-      _, status = Process.waitpid2(pid)
-      assert status.success?, status.inspect
-    end
     ru.close! if ru
   end
 
-- 
EW