Non-overriding signal handlers

lib/puma/cluster.rb

@@ -5,6 +5,7 @@
 require 'puma/plugin'
 require 'puma/cluster/worker_handle'
 require 'puma/cluster/worker'
+require 'puma/signal'
 
 require 'time'
 
@@ -288,7 +289,7 @@ def fork_worker!
     # of the signals handlers as small as possible.
     def setup_signals
       if @options[:fork_worker]
-        Signal.trap "SIGURG" do
+        Puma::Signal.trap "SIGURG" do
           fork_worker!
         end
 
@@ -302,23 +303,23 @@ def setup_signals
         end
       end
 
-      Signal.trap "SIGCHLD" do
+      Puma::Signal.trap "SIGCHLD" do
         wakeup!
       end
 
-      Signal.trap "TTIN" do
+      Puma::Signal.trap "TTIN" do
         @options[:workers] += 1
         wakeup!
       end
 
-      Signal.trap "TTOU" do
+      Puma::Signal.trap "TTOU" do
         @options[:workers] -= 1 if @options[:workers] >= 2
         wakeup!
       end
 
       master_pid = Process.pid
 
-      Signal.trap "SIGTERM" do
+      Puma::Signal.trap "SIGTERM" do
         # The worker installs their own SIGTERM when booted.
         # Until then, this is run by the worker and the worker
         # should just exit if they get it.
@@ -418,7 +419,7 @@ def run
 
       spawn_workers
 
-      Signal.trap "SIGINT" do
+      Puma::Signal.trap "SIGINT" do
         stop
       end
 

lib/puma/cluster/worker.rb

@@ -30,8 +30,9 @@ def run
         title += " [#{@options[:tag]}]" if @options[:tag] && !@options[:tag].empty?
         $0 = title
 
-        Signal.trap "SIGINT", "IGNORE"
-        Signal.trap "SIGCHLD", "DEFAULT"
+        Puma::Signal.trap "SIGINT", "IGNORE"
+
+        Puma::Signal.trap "SIGCHLD", "DEFAULT"
 
         Thread.new do
           Puma.set_thread_name "wrkr check"
@@ -55,7 +56,7 @@ def run
         @launcher.config.run_hooks(:before_worker_boot, index, @launcher.log_writer)
 
         begin
-        server = @server ||= start_server
+          server = @server ||= start_server
         rescue Exception => e
           log "! Unable to start worker"
           log e.backtrace[0]
@@ -69,7 +70,7 @@ def run
         if fork_worker
           restart_server.clear
           worker_pids = []
-          Signal.trap "SIGCHLD" do
+          Puma::Signal.trap "SIGCHLD" do
             wakeup! if worker_pids.reject! do |p|
               Process.wait(p, Process::WNOHANG) rescue true
             end
@@ -96,7 +97,7 @@ def run
           end
         end
 
-        Signal.trap "SIGTERM" do
+        Puma::Signal.trap "SIGTERM" do
           @worker_write << "e#{Process.pid}\n" rescue nil
           restart_server.clear
           server.stop

lib/puma/launcher.rb

@@ -7,6 +7,7 @@
 require 'puma/single'
 require 'puma/const'
 require 'puma/binder'
+require 'puma/signal'
 
 module Puma
   # Puma::Launcher is the single entry point for starting a Puma server based on user
@@ -415,7 +416,7 @@ def generate_restart_data
 
     def setup_signals
       begin
-        Signal.trap "SIGUSR2" do
+        Puma::Signal.trap "SIGUSR2" do
           restart
         end
       rescue Exception
@@ -424,7 +425,7 @@ def setup_signals
 
       unless Puma.jruby?
         begin
-          Signal.trap "SIGUSR1" do
+          Puma::Signal.trap "SIGUSR1" do
             phased_restart
           end
         rescue Exception
@@ -433,7 +434,7 @@ def setup_signals
       end
 
       begin
-        Signal.trap "SIGTERM" do
+        Puma::Signal.trap "SIGTERM" do
           # Shortcut the control flow in case raise_exception_on_sigterm is true
           do_graceful_stop
 
@@ -444,15 +445,15 @@ def setup_signals
       end
 
       begin
-        Signal.trap "SIGINT" do
+        Puma::Signal.trap "SIGINT" do
           stop
         end
       rescue Exception
         log "*** SIGINT not implemented, signal based gracefully stopping unavailable!"
       end
 
       begin
-        Signal.trap "SIGHUP" do
+        Puma::Signal.trap "SIGHUP" do
           if @runner.redirected_io?
             @runner.redirect_io
           else
@@ -465,7 +466,7 @@ def setup_signals
 
       begin
         unless Puma.jruby? # INFO in use by JVM already
-          Signal.trap "SIGINFO" do
+          Puma::Signal.trap "SIGINFO" do
             thread_status do |name, backtrace|
               @log_writer.log(name)
               @log_writer.log(backtrace.map { |bt| "  #{bt}" })

lib/puma/signal.rb

@@ -0,0 +1,51 @@
+module Puma
+  module Signal
+    module_function
+
+    def prepend_handler(sig, &handler)
+      name = signame(sig)
+      custom_signal_handlers[signame] ||= []
+      custom_signal_handlers[signame].prepend(handler)
+    end
+
+    # Signal.trap that does not replace
+    # the existing puma handlers
+    def trap(sig, handler_str=nil, &handler)
+      name = signame(sig)
+      ::Signal.trap(name) do
+        invoke_custom_signal_handlers(name)
+
+        if handler.respond_to?(:call)
+          yield handler
+        else
+          # dirty hack to call string handlers
+          # especially for DEFAULT and SYSTEM_DEFAULT
+          current_trap = ::Signal.trap(name, handler_str)
+          Process.kill(name, Process.pid)
+          ::Signal.trap(name, current_trap)
+        end
+      end
+    end
+
+    private
+
+    def signame(sig)
+      name = sig.is_a?(Integer) ? ::Signal.signame(sig) : String(sig).sub('SIG', '')
+      raise ArgumentError, "unsupported signal SIG#{name}" unless ::Signal.list[name]
+      name
+    end
+    module_function :signame
+
+    def invoke_custom_signal_handlers(signame)
+      Array(custom_signal_handlers[signame]).each do |handler|
+        yield handler
+      end
+    end
+    module_function :invoke_custom_signal_handlers
+
+    def custom_signal_handlers
+      @custom_signal_handlers ||= {}
+    end
+    module_function :custom_signal_handlers
+  end
+end