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* [PATCH] proxy_http_response: workaround non-terminated backends
@ 2016-04-06  6:25 Eric Wong
  2016-04-16  8:17 ` Eric Wong
  0 siblings, 1 reply; 3+ messages in thread
From: Eric Wong @ 2016-04-06  6:25 UTC (permalink / raw)
  To: yahns-public

Without this, we could only support persistent connections if
the backend gives a valid Content-Length or set
"Transfer-Encoding: chunked" in the response header.

Being good netizens, we want to use persistent connections as
much as possible if a remote client supports it; so perform
chunking ourselves when our remote clients are HTTP/1.1 and
able to decode chunked responses.

This is necessary to support some non-Rack HTTP/1.0-only
backend servers which rely on connection termination to
terminate responses.

Tested manually with a Perl PSGI application running under
"plackup".  Unlike Rack, the PSGI spec does not specify whether
the PSGI application or PSGI server should handle response
termination: git clone https://github.com/plack/psgi-specs.git
---
 lib/yahns/proxy_http_response.rb | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/lib/yahns/proxy_http_response.rb b/lib/yahns/proxy_http_response.rb
index 0a7e722..0e72d3a 100644
--- a/lib/yahns/proxy_http_response.rb
+++ b/lib/yahns/proxy_http_response.rb
@@ -68,6 +68,7 @@ def proxy_response_start(res, tip, kcar, req_res)
                 env['REQUEST_METHOD'] != 'HEAD'.freeze
     flags = MSG_DONTWAIT
     alive = @hs.next? && self.class.persistent_connections
+    term = false
     response_headers = env['yahns.proxy_pass.response_headers']
 
     res = "HTTP/1.1 #{msg ? %Q(#{code} #{msg}) : status}\r\n".dup
@@ -76,7 +77,10 @@ def proxy_response_start(res, tip, kcar, req_res)
       when /\A(?:Connection|Keep-Alive)\z/i
         next # do not let some upstream headers leak through
       when %r{\AContent-Length\z}i
+        term = true
         flags |= MSG_MORE if have_body && value.to_i > 0
+      when %r{\ATransfer-Encoding\z}i
+        term = true if value =~ /\bchunked\b/i
       end
 
       # response header mapping
@@ -92,6 +96,13 @@ def proxy_response_start(res, tip, kcar, req_res)
 
     # For now, do not add a Date: header, assume upstream already did it
     # but do not care if they did not
+
+    # chunk the response ourselves if the client supports it,
+    # but the backend does not terminate properly
+    if alive && ! term && (env['HTTP_VERSION'] == 'HTTP/1.1'.freeze)
+      res << "Transfer-Encoding: chunked\r\n".freeze
+      alive = true
+    end
     res << (alive ? "Connection: keep-alive\r\n\r\n".freeze
                   : "Connection: close\r\n\r\n".freeze)
 
@@ -154,6 +165,7 @@ def proxy_response_start(res, tip, kcar, req_res)
 
         case tmp = tip.shift || req_res.kgio_tryread(0x2000, rbuf)
         when String
+          tmp = chunk_out(tmp) if alive
           wbuf = proxy_write(wbuf, tmp, alive)
         when nil
           req_res.shutdown
@@ -174,7 +186,8 @@ def proxy_response_start(res, tip, kcar, req_res)
 
   def proxy_response_finish(kcar, wbuf, req_res)
     rbuf = Thread.current[:yahns_rbuf]
-    if len = kcar.body_bytes_left
+    alive = wbuf.wbuf_persist
+    if len = kcar.body_bytes_left # known Content-Length
 
       case tmp = req_res.kgio_tryread(0x2000, rbuf)
       when String
@@ -186,7 +199,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
         return :wait_readable # self remains in :ignore, wait on upstream
       end while len != 0
 
-    elsif kcar.chunked? # nasty chunked body
+    elsif kcar.chunked? # nasty chunked response body
       buf = ''.dup
 
       unless req_res.proxy_trailers
@@ -221,8 +234,10 @@ def proxy_response_finish(kcar, wbuf, req_res)
 
       case tmp = req_res.kgio_tryread(0x2000, rbuf)
       when String
+        tmp = chunk_out(tmp) if alive
         wbuf.wbuf_write(self, tmp)
       when nil
+        wbuf.wbuf_write(self, "0\r\n\r\n".freeze) if alive
         req_res.shutdown
         break
       when :wait_readable
@@ -232,7 +247,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
     end
 
     busy = wbuf.busy and return proxy_busy_mod_blocked(wbuf, busy)
-    proxy_busy_mod_done(wbuf.wbuf_persist) # returns nil
+    proxy_busy_mod_done(alive) # returns nil
   end
 
   def proxy_wait_next(qflags)
-- 
EW


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] proxy_http_response: workaround non-terminated backends
  2016-04-06  6:25 [PATCH] proxy_http_response: workaround non-terminated backends Eric Wong
@ 2016-04-16  8:17 ` Eric Wong
  2016-04-22  0:13   ` [PATCH] proxy_pass: honor wbuf_persist when ending response Eric Wong
  0 siblings, 1 reply; 3+ messages in thread
From: Eric Wong @ 2016-04-16  8:17 UTC (permalink / raw)
  To: yahns-public

Eric Wong <e@80x24.org> wrote:
> @@ -232,7 +247,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
>      end
>  
>      busy = wbuf.busy and return proxy_busy_mod_blocked(wbuf, busy)
> -    proxy_busy_mod_done(wbuf.wbuf_persist) # returns nil
> +    proxy_busy_mod_done(alive) # returns nil
>    end
>  
>    def proxy_wait_next(qflags)

Hm... that seems wrong,  The following fixup commit may be necessary.
Letting it run on our site for a few days before writing a commit
message and committing.  (Not really in a state of mind to be hacking
this time of year, but I noticed some high FD usage...)

--- a/lib/yahns/proxy_http_response.rb
+++ b/lib/yahns/proxy_http_response.rb
@@ -247,7 +247,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
     end
 
     busy = wbuf.busy and return proxy_busy_mod_blocked(wbuf, busy)
-    proxy_busy_mod_done(alive) # returns nil
+    proxy_busy_mod_done(alive && wbuf.wbuf_persist) # returns nil
   end
 
   def proxy_wait_next(qflags)

^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH] proxy_pass: honor wbuf_persist when ending response
  2016-04-16  8:17 ` Eric Wong
@ 2016-04-22  0:13   ` Eric Wong
  0 siblings, 0 replies; 3+ messages in thread
From: Eric Wong @ 2016-04-22  0:13 UTC (permalink / raw)
  To: yahns-public

If a static file response gets truncated while writing, we
set wbuf_persist to false in wbuf_flush of lib/yahns/wbuf_common.rb
Thus, we must check wbuf_persist attribute as late as possible
before yielding control back to the caller in proxy_response_finish
---
  A hopefully better version of what I proposed in:
  https://yhbt.net/yahns-public/20160416081712.GA21868@dcvr.yhbt.net/

 lib/yahns/proxy_http_response.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/yahns/proxy_http_response.rb b/lib/yahns/proxy_http_response.rb
index d0e3e41..c8a2a42 100644
--- a/lib/yahns/proxy_http_response.rb
+++ b/lib/yahns/proxy_http_response.rb
@@ -187,7 +187,6 @@ def proxy_response_start(res, tip, kcar, req_res)
 
   def proxy_response_finish(kcar, wbuf, req_res)
     rbuf = Thread.current[:yahns_rbuf]
-    alive = wbuf.wbuf_persist
     if len = kcar.body_bytes_left # known Content-Length
 
       case tmp = req_res.kgio_tryread(0x2000, rbuf)
@@ -233,6 +232,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
 
     else # no Content-Length or Transfer-Encoding: chunked, wait on EOF!
 
+      alive = wbuf.wbuf_persist
       case tmp = req_res.kgio_tryread(0x2000, rbuf)
       when String
         tmp = chunk_out(tmp) if alive
@@ -248,7 +248,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
     end
 
     busy = wbuf.busy and return proxy_busy_mod_blocked(wbuf, busy)
-    proxy_busy_mod_done(alive) # returns nil
+    proxy_busy_mod_done(wbuf.wbuf_persist) # returns nil
   end
 
   def proxy_wait_next(qflags)
-- 
EW

^ permalink raw reply	[flat|nested] 3+ messages in thread

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Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2016-04-06  6:25 [PATCH] proxy_http_response: workaround non-terminated backends Eric Wong
2016-04-16  8:17 ` Eric Wong
2016-04-22  0:13   ` [PATCH] proxy_pass: honor wbuf_persist when ending response Eric Wong

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