[PATCH] explain 11 byte magic number for self-pipe

[PATCH] explain 11 byte magic number for self-pipe

[Eric Wong]

Oops, this should've been explained long ago but apparently not.

In response to a comment on
http://www.sitepoint.com/the-self-pipe-trick-explained/

> Does anybody know why both unicorn and foreman read 11 bytes from
> self-pipe?

Unfortunately I couldn't find a way to comment on the site on a
JavaScript-free browser nor does it seem possible without
registering.

Again, anybody can send plain-text mail to:
unicorn-public@bogomips.org

No registration, no real name policy, no terms-of-service, just
plain-text.  Feel free to use Tor, mixmaster or any anonymity
service, too.
---
 lib/unicorn/http_server.rb | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb
index 015bd94..683eb82 100644
--- a/lib/unicorn/http_server.rb
+++ b/lib/unicorn/http_server.rb
@@ -370,6 +370,10 @@ class Unicorn::HttpServer
   # wait for a signal hander to wake us up and then consume the pipe
   def master_sleep(sec)
     IO.select([ @self_pipe[0] ], nil, nil, sec) or return
+    # 11 bytes is the maximum string length which can be embedded within
+    # the Ruby itself and not require a separate malloc (on 32-bit MRI 1.9+).
+    # Most reads are only one byte here and uncommon, so it's not worth a
+    # persistent buffer, either:
     @self_pipe[0].kgio_tryread(11)
   end
 
-- 
EW