test: cover http pipelining

test/functional/interface_http.py

@@ -105,5 +105,55 @@ class HTTPBasicsTest (BitcoinTestFramework):
         assert_equal(out1.status, http.client.BAD_REQUEST)
 
 
+        self.log.info("Check pipelining")
+        # Requests are responded to in order they were received
+        # See https://www.rfc-editor.org/rfc/rfc7230#section-6.3.2
+        tip_height = self.nodes[2].getblockcount()
+
+        req = "POST / HTTP/1.1\r\n"
+        req += f'Authorization: Basic {str_to_b64str(authpair)}\r\n'
+
+        # First request will take a long time to process
+        body1 = f'{{"method": "waitforblockheight", "params": [{tip_height + 1}]}}'
+        req1 = req
+        req1 += f'Content-Length: {len(body1)}\r\n\r\n'
+        req1 += body1
+
+        # Second request will process very fast
+        body2 = '{"method": "getblockcount"}'
+        req2 = req
+        req2 += f'Content-Length: {len(body2)}\r\n\r\n'
+        req2 += body2
+
+        # Get the underlying socket from HTTP connection so we can send something unusual
+        conn = http.client.HTTPConnection(urlNode2.hostname, urlNode2.port)
+        conn.connect()
+        sock = conn.sock
+        sock.settimeout(1)
+        # Send two requests in a row. The first will block the second indefinitely
+        sock.sendall(req1.encode("utf-8"))
+        sock.sendall(req2.encode("utf-8"))
+        try:
+            # The server should not respond to the fast, second request
+            # until the (very) slow first request has been handled:
+            res = sock.recv(1024)
+            assert not res
+        except TimeoutError:
+            pass
+
+        # Use a separate http connection to generate a block
+        self.generate(self.nodes[2], 1, sync_fun=self.no_op)
+
+        # Wait for two responses to be received
+        res = b""
+        while res.count(b"result") != 2:
+            res += sock.recv(1024)
+
+        # waitforblockheight was responded to first, and then getblockcount
+        # which includes the block added after the request was made
+        chunks = res.split(b'"result":')
+        assert chunks[1].startswith(b'{"hash":')
+        assert chunks[2].startswith(bytes(f'{tip_height + 1}', 'utf8'))
+
 if __name__ == '__main__':
     HTTPBasicsTest(__file__).main()