mongrel unicorn - Apr 2011 - Rails streaming example video

Aaron Patterson gladly provided us with a streaming video which I''ve
agreed to host:

http://unicorn.bogomips.org/streaming.ogv

If anybody has more Unicorn/Rainbows!-related videos/slides/etc in Free
Software-friendly formats, I''d be more than glad to host or mirror
them.

Thanks Aaron!

-- 
Eric Wong

Since streaming responses is becoming a topic nowadays, I figure we
should attempt to clarify configuration options relevant to it.

In general, I think the defaults for both Unicorn and Rainbows!  in
their targeted environments are reasonable and do not need more tuning.

I''ve pushed out the following two patches to
git://bogomips.org/unicorn.git:

* [PATCH 1/2] examples/nginx.conf: clarify proxy_buffering for Rails
* [PATCH 2/2] configurator: attempt to clarify

Feedback is greatly appreciated as always.

-- 
Eric Wong

I''ve tested with nginx 1.0.0 and confirmed "proxy_buffering
off;"
can cause Unicorn to block on a slow client reading a
large response.  While there''s a potential (client-visible)
performance improvement with Rails 3.1 streaming responses, it
can also hurt the server with slow clients.

Rainbows! with (ThreadSpawn or ThreadPool) is probably the best
way to do streaming responses efficiently from all angles (from
a server, client and programmer time perspective).
---
 examples/nginx.conf |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/examples/nginx.conf b/examples/nginx.conf
index 52ec245..9f245c8 100644
--- a/examples/nginx.conf
+++ b/examples/nginx.conf
@@ -125,10 +125,15 @@ http {
       proxy_redirect off;
 
       # set "proxy_buffering off" *only* for Rainbows! when doing
-      # Comet/long-poll stuff.  It''s also safe to set if
you''re
-      # using only serving fast clients with Unicorn + nginx.
-      # Otherwise you _want_ nginx to buffer responses to slow
-      # clients, really.
+      # Comet/long-poll/streaming.  It''s also safe to set if
you''re using
+      # only serving fast clients with Unicorn + nginx, but not slow
+      # clients.  You normally want nginx to buffer responses to slow
+      # clients, even with Rails 3.1 streaming because otherwise a slow
+      # client can become a bottleneck of Unicorn.
+      #
+      # The Rack application may also set "X-Accel-Buffering
(yes|no)"
+      # in the response headers do disable/enable buffering on a
+      # per-response basis.
       # proxy_buffering off;
 
       proxy_pass http://app_server;
-- 
Eric Wong

These options will probably be more important as interest in
streaming responses in Rails 3.1 develops.

I consider the respective defaults for Unicorn (designed to run
behind nginx) and Rainbows! (designed to run standalone) to be
the best choices in their respective environments.
---
 lib/unicorn/configurator.rb |   22 +++++++++++++++-------
 1 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/lib/unicorn/configurator.rb b/lib/unicorn/configurator.rb
index 73869de..bed3abe 100644
--- a/lib/unicorn/configurator.rb
+++ b/lib/unicorn/configurator.rb
@@ -253,24 +253,32 @@ class Unicorn::Configurator
   #
   # [:tcp_nodelay => true or false]
   #
-  #   Disables Nagle''s algorithm on TCP sockets if +true+
+  #   Disables Nagle''s algorithm on TCP sockets if +true+.
+  #
+  #   Setting this to +true+ can make streaming responses in Rails 3.1
+  #   appear more quickly at the cost of slightly higher bandwidth usage.
+  #   The effect of this option is most visible if nginx is not used,
+  #   but nginx remains highly recommended with \Unicorn.
   #
   #   This has no effect on UNIX sockets.
   #
-  #   Default: operating system defaults (usually Nagle''s algorithm
enabled)
+  #   Default: +false+ (Nagle''s algorithm enabled) in \Unicorn,
+  #   +true+ in Rainbows!
   #
   # [:tcp_nopush => true or false]
   #
   #   Enables/disables TCP_CORK in Linux or TCP_NOPUSH in FreeBSD
   #
-  #   This is enabled by default as of Unicorn 3.4.  This prevents partial
-  #   TCP frames from being sent out and reduces wakeups in nginx if it is
-  #   on a different machine.  Since Unicorn is only designed for applications
-  #   that send the response body quickly without keepalive, sockets will
-  #   always be flushed on close to prevent delays.
+  #   This prevents partial TCP frames from being sent out and reduces
+  #   wakeups in nginx if it is on a different machine.  Since \Unicorn
+  #   is only designed for applications that send the response body
+  #   quickly without keepalive, sockets will always be flushed on close
+  #   to prevent delays.
   #
   #   This has no effect on UNIX sockets.
   #
+  #   Default: +true+ in \Unicorn 3.4+, +false+ in Rainbows!
+  #
   # [:tries => Integer]
   #
   #   Times to retry binding a socket if it is already in use
-- 
Eric Wong