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authorEric Wong <>2014-10-04 02:14:21 +0000
committerEric Wong <>2015-04-22 18:55:32 +0000
commit5176868d908b03dbd4d43c7fcc5545bccc2b138a (patch)
parent2bb8cc404232254af0d74f2dd3dec87d406fd764 (diff)
There may be code in a before_fork hook which should run only once,
document an example using a guard variable since it may not be
immediately obvious to all users.

Inspired-by: BrĂ¡ulio Bhavamitra <>
1 files changed, 11 insertions, 0 deletions
diff --git a/examples/unicorn.conf.rb b/examples/unicorn.conf.rb
index 9dce58a..4b28a5a 100644
--- a/examples/unicorn.conf.rb
+++ b/examples/unicorn.conf.rb
@@ -54,12 +54,23 @@ GC.respond_to?(:copy_on_write_friendly=) and
 # fast LAN.
 check_client_connection false
+# local variable to guard against running a hook multiple times
+run_once = true
 before_fork do |server, worker|
   # the following is highly recomended for Rails + "preload_app true"
   # as there's no need for the master process to hold a connection
   defined?(ActiveRecord::Base) and
+  # Occasionally, it may be necessary to run non-idempotent code in the
+  # master before forking.  Keep in mind the above disconnect! example
+  # is idempotent and does not need a guard.
+  if run_once
+    # do_something_once_here ...
+    run_once = false # prevent from firing again
+  end
   # The following is only recommended for memory/DB-constrained
   # installations.  It is not needed if your system can house
   # twice as many worker_processes as you have configured.