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From: Eric Wong <e@80x24.org>
To: yahns-public@yhbt.net
Subject: [PATCH] proxy_http_response: workaround non-terminated backends
Date: Wed,  6 Apr 2016 06:25:56 +0000	[thread overview]
Message-ID: <20160406062556.10988-1-e@80x24.org> (raw)

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
       # 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
@@ -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
       when :wait_readable
@@ -232,7 +247,7 @@ def proxy_response_finish(kcar, wbuf, req_res)
     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
   def proxy_wait_next(qflags)

             reply	other threads:[~2016-04-06  6:25 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-06  6:25 Eric Wong [this message]
2016-04-16  8:17 ` [PATCH] proxy_http_response: workaround non-terminated backends Eric Wong
2016-04-22  0:13   ` [PATCH] proxy_pass: honor wbuf_persist when ending response Eric Wong

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