[PATCH] initialize signal handlers before writing pid file

Eric Wong normalperson at yhbt.net
Tue Jan 19 21:38:26 EST 2010


This prevents trigger-happy init scripts from reading the pid
file (and thus sending signals) to a not-fully initialized
master process to handle them.

This does NOT fix anything if other processes are sending
signals prematurely without relying on the presence of the pid
file.  It's not possible to prevent all cases of this in one
process, even in a purely C application, so we won't bother
trying.

We continue to always defer signal handling to the main loop
anyways, and signals sent to the master process will be
deferred/ignored until Unicorn::HttpServer#join is run.
---
  Eric Wong <normalperson at yhbt.net> wrote:
  > I'll look into what the consequences of writing the pid file after
  > signal handlers are setup later this week.

  I just pushed this out to git://git.bogomips.org/unicorn.git

  There were some test cases (that shouldn't be called "unit tests")
  that needed to be fixed but I don't think anything else is broken,
  but be sure to let us know either way.

 lib/unicorn.rb            |   16 +++++++++++-----
 test/test_helper.rb       |    5 +++++
 test/unit/test_server.rb  |    1 +
 test/unit/test_signals.rb |    6 +++++-
 test/unit/test_upload.rb  |    1 +
 5 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index 7a1ef34..e3e4315 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -210,7 +210,18 @@ module Unicorn
       end
       config_listeners.each { |addr| listen(addr) }
       raise ArgumentError, "no listeners" if LISTENERS.empty?
+
+      # this pipe is used to wake us up from select(2) in #join when signals
+      # are trapped.  See trap_deferred.
+      init_self_pipe!
+
+      # 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_deferred(sig) }
+      trap(:CHLD) { |_| awaken_master }
       self.pid = config[:pid]
+
       self.master_pid = $$
       build_app! if preload_app
       maintain_worker_count
@@ -322,14 +333,9 @@ module Unicorn
     # one-at-a-time time and we'll happily drop signals in case somebody
     # is signalling us too often.
     def join
-      # this pipe is used to wake us up from select(2) in #join when signals
-      # are trapped.  See trap_deferred
-      init_self_pipe!
       respawn = true
       last_check = Time.now
 
-      QUEUE_SIGS.each { |sig| trap_deferred(sig) }
-      trap(:CHLD) { |sig_nr| awaken_master }
       proc_name 'master'
       logger.info "master process ready" # test_exec.rb relies on this message
       if ready_pipe
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 3bdbeb1..5b750ee 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -294,3 +294,8 @@ def chunked_spawn(stdout, *cmd)
     end while true
   }
 end
+
+def reset_sig_handlers
+  sigs = %w(CHLD).concat(Unicorn::HttpServer::QUEUE_SIGS)
+  sigs.each { |sig| trap(sig, "DEFAULT") }
+end
diff --git a/test/unit/test_server.rb b/test/unit/test_server.rb
index 00705d0..36333a0 100644
--- a/test/unit/test_server.rb
+++ b/test/unit/test_server.rb
@@ -41,6 +41,7 @@ class WebServerTest < Test::Unit::TestCase
       File.truncate("test_stderr.#$$.log", 0)
       @server.stop(true)
     end
+    reset_sig_handlers
   end
 
   def test_preload_app_config
diff --git a/test/unit/test_signals.rb b/test/unit/test_signals.rb
index eb2af0b..71cf8f4 100644
--- a/test/unit/test_signals.rb
+++ b/test/unit/test_signals.rb
@@ -40,6 +40,10 @@ class SignalsTest < Test::Unit::TestCase
     @server = nil
   end
 
+  def teardown
+    reset_sig_handlers
+  end
+
   def test_worker_dies_on_dead_master
     pid = fork {
       app = lambda { |env| [ 200, {'X-Pid' => "#$$" }, [] ] }
@@ -190,7 +194,7 @@ class SignalsTest < Test::Unit::TestCase
     killer = fork { loop { Process.kill(:HUP, pid); sleep(0.0001) } }
     buf = ' ' * @bs
     @count.times { sock.syswrite(buf) }
-    Process.kill(:TERM, killer)
+    Process.kill(:KILL, killer)
     Process.waitpid2(killer)
     redirect_test_io { @server.stop(true) }
     # can't check for == since pending signals get merged
diff --git a/test/unit/test_upload.rb b/test/unit/test_upload.rb
index 7ac3c9e..dc0eb40 100644
--- a/test/unit/test_upload.rb
+++ b/test/unit/test_upload.rb
@@ -55,6 +55,7 @@ class UploadTest < Test::Unit::TestCase
   def teardown
     redirect_test_io { @server.stop(true) } if @server
     @random.close
+    reset_sig_handlers
   end
 
   def test_put
-- 
Eric Wong


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