[PATCH] Rescue failed pipe resizes due to permissions

[sdemjanenko@gmail.com]

From: Stephen Demjanenko <sdemjanenko@gmail.com>

When running: ```
require 'kgio'
require 'raindrops'

F_SETPIPE_SZ = 1031 if RUBY_PLATFORM =~ /linux/

Kgio::Pipe.new.each do |io|
  io.close_on_exec = true
  if defined?(F_SETPIPE_SZ)
    begin
      puts "setting"
      io.fcntl(F_SETPIPE_SZ, Raindrops::PAGE_SIZE)
    rescue Errno::EINVAL
      puts "rescued"
    rescue => e
      puts ["FAILED HARD", e].inspect
    end
  end
end
```
on a few servers to test some Unicorn boot failures I saw:
```
["FAILED HARD", #<Errno::EPERM: Operation not permitted>]
```

The `EPERM` error gets raised by the Linux kernel if:
```
(too_many_pipe_buffers_hard(pipe->user) ||
too_many_pipe_buffers_soft(pipe->user)) &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)
```

Given that the resize is not strictly necessary Unicorn should
rescue the error and continue booting.
---
 lib/unicorn.rb | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index 5f2134d..dd5dff4 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -123,6 +123,9 @@ def self.pipe # :nodoc:
           io.fcntl(F_SETPIPE_SZ, Raindrops::PAGE_SIZE)
         rescue Errno::EINVAL
           # old kernel
+        rescue Errno::EPERM
+          # resizes fail if Linux is close to the pipe limit for the user
+          # or if the user does not have permissions to resize
         end
       end
     end
-- 
2.7.4