Re: [ANN] unicorn 0.990.0 - inching towards 1.0

[Eric Wong <normalperson@yhbt.net>]

Alexander Simonov <alex@simonov.me> wrote:
> On Jun 10, 2010, at 10:38 AM, Eric Wong wrote:
> > And again (I seem to remember saying this months ago), any time you're
> > deploying, you should be paying extra attention to the app anyways.
> > That means testing with actual HTTP requests, not just seeing of the
> > process is up.  Just having a running process serving error pages is
> > equally worthless as not running the server at all.
> 
> Hm.. It's makes sense.
> But much better if it will be writing in the documentation for the future.

Here's what I've pushed out, let me know if everything makes
sense.  I think I'll release 0.991.0 in a little bit.

>From f9baab18705218dae4c37c2c92d1ceea151bba8e Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Thu, 10 Jun 2010 17:57:08 -0700
Subject: [PATCH] docs: hopefully clarify preload_app=false behavior

While we're at it, inform people of why they might use
a symlink
---
 SIGNALS                     |    7 ++++++-
 lib/unicorn/configurator.rb |   21 ++++++++++++++++++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/SIGNALS b/SIGNALS
index be96892..8851775 100644
--- a/SIGNALS
+++ b/SIGNALS
@@ -14,7 +14,12 @@ Unicorn and nginx.
   will also pick up any application code changes when restarted.  If
   "preload_app" is true, then application code changes will have no
   effect; USR2 + QUIT (see below) must be used to load newer code in
-  this case.
+  this case.  When reloading the application, +Gem.refresh+ will
+  be called so updated code for your application can pick up newly
+  installed RubyGems.  It is not recommended that you uninstall
+  libraries your application depends on while Unicorn is running,
+  as respawned workers may enter a spawn loop when they fail to
+  load an uninstalled dependency.
 
 * INT/TERM - quick shutdown, kills all workers immediately
 
diff --git a/lib/unicorn/configurator.rb b/lib/unicorn/configurator.rb
index 71c7a8a..533e0ed 100644
--- a/lib/unicorn/configurator.rb
+++ b/lib/unicorn/configurator.rb
@@ -311,7 +311,22 @@ module Unicorn
     #
     # In addition to reloading the unicorn-specific config settings,
     # SIGHUP will reload application code in the working
-    # directory/symlink when workers are gracefully restarted.
+    # directory/symlink when workers are gracefully restarted when
+    # preload_app=false (the default).  As reloading the application
+    # sometimes requires RubyGems updates, +Gem.refresh+ is always
+    # called before the application is loaded (for RubyGems users).
+    #
+    # During deployments, care should _always_ be taken to ensure your
+    # applications are properly deployed and running.  Using
+    # preload_app=false (the default) means you _must_ check if
+    # your application is responding properly after a deployment.
+    # Improperly deployed applications can go into a spawn loop
+    # if the application fails to load.  While your children are
+    # in a spawn loop, it is is possible to fix an application
+    # by properly deploying all required code and dependencies.
+    # Using preload_app=true means any application load error will
+    # cause the master process to exit with an error.
+
     def preload_app(bool)
       case bool
       when TrueClass, FalseClass
@@ -344,9 +359,9 @@ module Unicorn
       set_path(:stdout_path, path)
     end
 
-    # sets the working directory for Unicorn.  This ensures USR2 will
+    # sets the working directory for Unicorn.  This ensures SIGUSR2 will
     # start a new instance of Unicorn in this directory.  This may be
-    # a symlink.
+    # a symlink, a common scenario for Capistrano users.
     def working_directory(path)
       # just let chdir raise errors
       path = File.expand_path(path)
-- 
Eric Wong
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