* [PATCH] proxy_pass: simplify writing request bodies upstream
@ 2016-05-04 3:51 Eric Wong
0 siblings, 0 replies; only message in thread
From: Eric Wong @ 2016-05-04 3:51 UTC (permalink / raw)
To: spew
The cost of extra branches inside is negligible compared to
the cost of all the other method calls we make. Favor
smaller code instead and inline some (now) single-use methods.
Furthermore, this allows us to reuse the request header buffer
instead of relying on thread-local storage and potentially
having to to swap buffers.
In retrospect, there may be no such thing as a tight read-write
I/O loop where removing branches is beneficial given the cost of
reads and writes.
---
lib/yahns/proxy_pass.rb | 112 +++++++++++++++++++++---------------------------
1 file changed, 49 insertions(+), 63 deletions(-)
diff --git a/lib/yahns/proxy_pass.rb b/lib/yahns/proxy_pass.rb
index 148957b..a2d7d81 100644
--- a/lib/yahns/proxy_pass.rb
+++ b/lib/yahns/proxy_pass.rb
@@ -22,12 +22,6 @@ def req_start(c, req, input, chunked)
Thread.current[:yahns_queue].queue_add(self, Yahns::Queue::QEV_WR)
end
- # we must reinitialize the thread-local rbuf if it may get beyond the
- # current thread
- def detach_rbuf!
- Thread.current[:yahns_rbuf] = ''.dup
- end
-
def yahns_step # yahns event loop entry point
c = @yahns_client
case req = @rrstate
@@ -42,7 +36,9 @@ def yahns_step # yahns event loop entry point
if res = req.headers(@hdr = [], rv)
return c.proxy_response_start(res, rv, req, self)
else # ugh, big headers or tricked response
- buf = detach_rbuf!
+ # we must reinitialize the thread-local rbuf if it may
+ # live beyond the current thread
+ buf = Thread.current[:yahns_rbuf] = ''.dup
@resbuf = rv
end
# continue looping in middle "case @resbuf" loop
@@ -83,64 +79,63 @@ def yahns_step # yahns event loop entry point
c.proxy_err_response(502, self, e, wbuf)
end
- # returns :wait_readable if complete, :wait_writable if not
- def send_req_body(req)
- buf, input, chunked = req
-
- # get the first buffered chunk or vector
+ def send_req_body_chunk(buf)
case rv = String === buf ? kgio_trywrite(buf) : kgio_trywritev(buf)
when String, Array
- buf = rv # retry inner loop
- when :wait_writable
- req[0] = buf
- return :wait_writable
- when nil
- break # onto writing body
+ buf.replace(rv) # retry loop on partial write
+ when :wait_writable, nil
+ # :wait_writable = upstream is reading slowly and making us wait
+ return rv
+ else
+ abort "BUG: #{rv.inspect} from kgio_trywrite*"
end while true
+ end
- buf = Thread.current[:yahns_rbuf]
+ # returns :wait_readable if complete, :wait_writable if not
+ def send_req_body(req) # @rrstate == [ (str|vec), rack.input, chunked? ]
+ buf, input, chunked = req
- # Note: input (env['rack.input']) is fully-buffered by default so
- # we should not be waiting on a slow network resource when reading
- # input. However, some weird configs may disable this on LANs
+ # send the first buffered chunk or vector
+ rv = send_req_body_chunk(buf) and return rv # :wait_writable
+ # yay, sent the first chunk, now read the body!
+ rbuf = buf
if chunked
- while input.read(0x2000, buf)
- vec = [ "#{buf.size.to_s(16)}\r\n", buf, "\r\n".freeze ]
- case rv = kgio_trywritev(vec)
- when Array
- vec = rv # partial write, retry in case loop
- when :wait_writable
- detach_rbuf!
- req[0] = vec
- return :wait_writable
- when nil
- break # continue onto reading next chunk
- end while true
+ if String === buf # initial body
+ req[0] = buf = []
+ else
+ # try to reuse the biggest non-frozen buffer we just wrote;
+ rbuf = buf.max_by(&:size)
+ rbuf = ''.dup if rbuf.frozen? # unlikely...
end
- close_req_body(input)
-
- # note: we do not send any trailer, they are folded into the header
- # because this relies on full request buffering
- send_req_buf("0\r\n\r\n".freeze)
- # prepare_wait_readable already called by send_req_buf
- else # identity request, easy:
- while input.read(0x2000, buf)
- case rv = kgio_trywrite(buf)
- when String
- buf = rv # partial write, retry in case loop
- when :wait_writable
- detach_rbuf!
- req[0] = buf
- return :wait_writable
- when nil
- break # continue onto reading next block
- end while true
+ end
+
+ # Note: input (env['rack.input']) is fully-buffered by default so
+ # we should not be waiting on a slow network resource when reading
+ # input. However, some weird configs may disable this on LANs
+ # and we may wait indefinitely on input.read here...
+ while input.read(0x2000, rbuf)
+ if chunked
+ buf[0] = "#{rbuf.size.to_s(16)}\r\n".freeze
+ buf[1] = rbuf
+ buf[2] = "\r\n".freeze
end
+ rv = send_req_body_chunk(buf) and return rv # :wait_writable
+ end
+
+ rbuf.clear # all done, clear the big buffer
- close_req_body(input)
- prepare_wait_readable
+ # we cannot use respond_to?(:close) here since Rack::Lint::InputWrapper
+ # tries to prevent that (and hijack means all Rack specs go out the door)
+ case input
+ when Yahns::TeeInput, IO
+ input.close
end
+
+ # note: we do not send any trailer, they are folded into the header
+ # because this relies on full request buffering
+ # prepare_wait_readable is called by send_req_buf
+ chunked ? send_req_buf("0\r\n\r\n".freeze) : prepare_wait_readable
rescue Errno::EPIPE, Errno::ECONNRESET, Errno::ENOTCONN
# no more reading off the client socket, just prepare to forward
# the rejection response from the upstream (if any)
@@ -153,15 +148,6 @@ def prepare_wait_readable
:wait_readable # all done sending the request, wait for response
end
- def close_req_body(input)
- # we cannot use respond_to?(:close) here since Rack::Lint::InputWrapper
- # tries to prevent that (and hijack means all Rack specs go out the door)
- case input
- when Yahns::TeeInput, IO
- input.close
- end
- end
-
# n.b. buf must be a detached string not shared with
# Thread.current[:yahns_rbuf] of any thread
def send_req_buf(buf)
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2016-05-04 3:51 [PATCH] proxy_pass: simplify writing request bodies upstream Eric Wong
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