From f9d110fabfcd1063801fe30566a4cd543820978d Mon Sep 17 00:00:00 2001
From: Brandon Dunne <bdunne@redhat.com>
Date: Tue, 7 May 2013 15:42:43 -0400
Subject: [PATCH] Fix issue related to command output filling up the IO pipe.

If command being run had output of more than 64k,the pipe would fill and
the process would hang waiting for room to write more data into the pipe.
Reading the pipe synchrously eliminates the problem.
See the following link for more detail on the problem and another solution.
http://stackoverflow.com/questions/13829830/ruby-process-spawn-stdout-pipe-buffer-size-limit/13846146#13846146
---
 lib/linux_admin/common.rb | 53 +++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 8 deletions(-)

diff --git a/lib/linux_admin/common.rb b/lib/linux_admin/common.rb
index 847bf19..f45464a 100644
--- a/lib/linux_admin/common.rb
+++ b/lib/linux_admin/common.rb
@@ -2,20 +2,57 @@ module LinuxAdmin
   module Common
     def self.run(cmd, options = {})
       begin
-        r, w = IO.pipe
-        pid, status = Process.wait2(Kernel.spawn(cmd, :err => [:child, :out], :out => w))
-        w.close
-        if options[:return_output] && status.exitstatus == 0
-          r.read
-        elsif options[:return_exitstatus] || status.exitstatus == 0
-          status.exitstatus
+        out = launch(cmd)
+        if options[:return_output] && exitstatus == 0
+          out
+        elsif options[:return_exitstatus] || exitstatus == 0
+          exitstatus
         else
-          raise "Error: Exit Code #{status.exitstatus}"
+          raise "Error: Exit Code #{exitstatus}"
         end
       rescue
         return nil if options[:return_exitstatus]
         raise
+      ensure
+        self.exitstatus = nil
       end
     end
+
+    private
+
+    # IO pipes have a maximum size of 64k before blocking,
+    # so we need to read and write synchronously.
+    # http://stackoverflow.com/questions/13829830/ruby-process-spawn-stdout-pipe-buffer-size-limit/13846146#13846146
+    THREAD_SYNC_KEY = "LinuxAdmin-exitstatus"
+
+    def self.launch(cmd)
+      pipe_r, pipe_w = IO.pipe
+      pid = Kernel.spawn(cmd, :err => [:child, :out], :out => pipe_w)
+      wait_for_process(pid, pipe_w)
+      wait_for_output(pipe_r)
+    end
+
+    def self.wait_for_process(pid, pipe_w)
+      self.exitstatus = :not_done
+      Thread.new(Thread.current) do |parent_thread|
+        _, status = Process.wait2(pid)
+        pipe_w.close
+        parent_thread[THREAD_SYNC_KEY] = status.exitstatus
+      end
+    end
+
+    def self.wait_for_output(pipe_r)
+      out = pipe_r.read
+      sleep(0.1) while exitstatus == :not_done
+      return out
+    end
+
+    def self.exitstatus
+      Thread.current[THREAD_SYNC_KEY]
+    end
+
+    def self.exitstatus=(value)
+      Thread.current[THREAD_SYNC_KEY] = value
+    end
   end
 end
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