gracefully die if working dir is invalid at fork

In nearly every app, if the current working directory
disappears, the app becomes broken, sometimes subtly.  It can be
especially broken when preload_app is false (the default).

So just shut ourselves down to spare ourselves the
wasted CPU cycles on a dead app.

As a (hopefully) pleasant side effect, this allows
configurations with preload_app==false (the default) to do
application code reloads via SIGHUP (in addition to unicorn
config reloads).

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index d442f63..4f7d417 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -53,6 +53,7 @@ module Unicorn
       @start_ctx = DEFAULT_START_CTX.dup
       @start_ctx.merge!(start_ctx) if start_ctx
       @app = app
+      @alive = true
       @mode = :idle
       @master_pid = $$
       @workers = Hash.new
@@ -165,7 +166,7 @@ module Unicorn
       $0 = "unicorn master"
       logger.info "master process ready" # test relies on this message
       begin
-        loop do
+        while @alive
           reap_all_workers
           case @mode
           when :idle
@@ -352,6 +353,13 @@ module Unicorn
       return if @workers.size == @worker_processes
       (0...@worker_processes).each do |worker_nr|
         @workers.values.include?(worker_nr) and next
+        begin
+          Dir.chdir(@start_ctx[:cwd])
+        rescue Errno::ENOENT => err
+          logger.fatal "#{err.inspect} (#{@start_ctx[:cwd]})"
+          @alive = false
+          return
+        end
         tempfile = Tempfile.new('') # as short as possible to save dir space
         tempfile.unlink # don't allow other processes to find or see it
         tempfile.sync = true