HTTPTransport test: Deal with limited-size pipe buffers

util/net/http_transport_test_server.py

Index: util/net/http_transport_test_server.py
diff --git a/util/net/http_transport_test_server.py b/util/net/http_transport_test_server.py
index ecf71d702fe7922ef1bef3269f22a40838662bba..4558f0f5820aea415cc4f58587695960c378dcaf 100755
--- a/util/net/http_transport_test_server.py
+++ b/util/net/http_transport_test_server.py
@@ -58,6 +58,14 @@ class BufferedReadFile(object):
     self.file.close()
 
 
+# Everything to be written to stdout is collected into this string. It can’t be
+# written to stdout until after the HTTP transaction is complete, because
+# stdout is a pipe being read by a test program that’s also the HTTP client. The
+# test program expects to complete the entire HTTP transaction before it even
+# starts reading this script’s stdout. If the stdout pipe buffer fills up during
+# an HTTP transaction, deadlock would result.
+to_write_to_stdout = ''

[Mark Mentovai, 2015/08/18 21:26:19]

I don’t like that this is a global, but BaseHTTPServer has this silly interface
where you give it a class instead of an object, so I don’t think there’s really
a better place to put this. Suggestions welcome.

[Robert Sesek, 2015/08/18 21:42:49]

You could move it to RequestHandler.written_response_body, but it'll still be
global state.

+
 class RequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
   response_code = 500
   response_body = ''
@@ -69,9 +77,9 @@ class RequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
     BaseHTTPServer.BaseHTTPRequestHandler.handle_one_request(self)
 
   def do_POST(self):
-    writer = sys.stdout
+    global to_write_to_stdout
 
-    writer.write(self.rfile.buffer)
+    to_write_to_stdout = self.rfile.buffer
     self.rfile.buffer = ''
 
     if self.headers.get('Transfer-Encoding', '') == 'Chunked':
@@ -80,15 +88,14 @@ class RequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
       length = int(self.headers.get('Content-Length', -1))
       body = self.rfile.read(length)
 
+    to_write_to_stdout += body
+
     self.send_response(self.response_code)
     self.end_headers()
     if self.response_code == 200:
       self.wfile.write(self.response_body)
       self.wfile.write('\r\n')
 
-    writer.write(body)
-    writer.flush()
-
   def handle_chunked_encoding(self):
     """This parses a "Transfer-Encoding: Chunked" body in accordance with
     RFC 7230 §4.1. This returns the result as a string.
@@ -146,5 +153,9 @@ def Main():
   # Handle the request.
   server.handle_request()
 
+  # Share the entire request with the test program, which will validate it.
+  sys.stdout.write(to_write_to_stdout)
+  sys.stdout.flush()
+
 if __name__ == '__main__':
   Main()