Unicorn_rails ignores USR2 signal

Yeung, Jeffrey Jeffrey.Yeung at polycom.com
Fri Mar 30 22:16:38 UTC 2012

I have little to report, unfortunately.  I still have not identified what is trapping USR2 in my application, if something is indeed doing that.

I've attempted to do a bit more investigation work in my spare time this week, and the results are still rather mysterious.

First, I applied your patch to http_server.rb that you suggested in this thread back on March 9th (quoted below), which re-overrides the signal handlers in build_app!().  The patch did work.  Okay, that seems to reconfirm that the app is doing something with the USR2 signal handler...

Then I modified the master_siginit() method a bit further to provide more info:
  def master_siginit
    QUEUE_SIGS.each { |sig|
      old_handler = trap(sig) { SIG_QUEUE << sig; awaken_master }
      logger.info("old handler for #{sig.to_s}: #{old_handler.inspect}")
    trap(:CHLD) { awaken_master }

And the output was a bit surprising.  Here is the Unicorn stderr log when starting up the service.  master_siginit() is called twice, as expected...

I, [2012-03-30T14:57:51.301839 #15828]  INFO -- : listening on addr= fd=3
I, [2012-03-30T14:57:51.302341 #15828]  INFO -- : old handler for WINCH: nil
I, [2012-03-30T14:57:51.302435 #15828]  INFO -- : old handler for QUIT: "DEFAULT"
I, [2012-03-30T14:57:51.302505 #15828]  INFO -- : old handler for INT: "DEFAULT"
I, [2012-03-30T14:57:51.302573 #15828]  INFO -- : old handler for TERM: "DEFAULT"
I, [2012-03-30T14:57:51.302641 #15828]  INFO -- : old handler for USR1: "DEFAULT"
I, [2012-03-30T14:57:51.302709 #15828]  INFO -- : old handler for USR2: "DEFAULT"
I, [2012-03-30T14:57:51.302786 #15828]  INFO -- : old handler for HUP: "DEFAULT"
I, [2012-03-30T14:57:51.302853 #15828]  INFO -- : old handler for TTIN: nil
I, [2012-03-30T14:57:51.302917 #15828]  INFO -- : old handler for TTOU: nil
I, [2012-03-30T14:57:51.303502 #15828]  INFO -- : Refreshing Gem list
old handler for WINCH: #<Proc:0x00000002d97488@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for QUIT: #<Proc:0x00000002d97098@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for INT: #<Proc:0x00000002d96c70@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for TERM: #<Proc:0x00000002d96848@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for USR1: #<Proc:0x00000002d96420@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for USR2: #<Proc:0x00000002d95ff8@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for HUP: #<Proc:0x00000002d95bd0@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for TTIN: #<Proc:0x00000002d957a8@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
old handler for TTOU: #<Proc:0x00000002d953b8@/usr/local/lib/ruby/gems/1.9.1/gems/unicorn-4.2.0/lib/unicorn/http_server.rb:745>
master process ready
worker=0 ready

Which to me, looks like the USR2 handler was unchanged in the second master_siginit() call.  Yet, if I remove that second master_siginit() call from there, USR2 ceases to work.  :S


-----Original Message-----
diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb index 7d2c623..1b9d693 100644
--- a/lib/unicorn/http_server.rb
+++ b/lib/unicorn/http_server.rb
@@ -128,8 +128,7 @@ class Unicorn::HttpServer
     # setup signal handlers before writing pid file in case people get
     # trigger happy and send signals as soon as the pid file exists.
     # Note that signals don't actually get handled until the #join method
-    QUEUE_SIGS.each { |sig| trap(sig) { SIG_QUEUE << sig; awaken_master } }
-    trap(:CHLD) { awaken_master }
+    master_siginit
     self.pid = config[:pid]
     self.master_pid = $$
@@ -689,6 +688,9 @@ class Unicorn::HttpServer
       self.app = app.call
+      # override signal handlers the app may have set
+      master_siginit if preload_app
@@ -736,4 +738,9 @@ class Unicorn::HttpServer
     config_listeners.each { |addr| listen(addr) }
     raise ArgumentError, "no listeners" if LISTENERS.empty?
+  def master_siginit
+    QUEUE_SIGS.each { |sig| trap(sig) { SIG_QUEUE << sig; awaken_master } }
+    trap(:CHLD) { awaken_master }
+  end

More information about the mongrel-unicorn mailing list