senders: resolve and use a random address on websockets connect

Resolve websocket remote address and pick a random one as an explicit
host to connect. The combination of asyncio websockets and asyncio
create_connect() have some overlapping timeouts that lead to connection
attempts to run through the whole list of targets returned by
getaddrinfo(). This breaks connectivity in some dual stack IPv6/IPv4
cases, when either one of the address family has e.g. routing problems.

We can fairly safely pick one at random here; we have retry logic built
around the connections anyway that eventually lead to connected state.

Author: hnousiainen

journalpump/senders/websocket.py

@@ -12,11 +12,13 @@
 import contextlib
 import enum
 import logging
+import random
 import snappy  # pylint: disable=import-error
 import socket
 import ssl
 import time
-import websockets
+import websockets.client
+import websockets.exceptions
 
 
 @enum.unique
@@ -163,6 +165,8 @@ async def websocket_connect_coro(self):
 
         sock = None
         url_parsed = urlparse(self.websocket_uri)
+        preferred_host = None
+
         if self.socks5_proxy:
             socks_url_parsed = urlparse(self.socks5_proxy_url)
             self.log.info(
@@ -176,10 +180,27 @@ async def websocket_connect_coro(self):
                 socks_url_parsed.hostname,
                 socks_url_parsed.port,
             )
+        else:
+            # Resolve hostname and pick one address at random
+            # Websockets.connect() and underlying asyncio.loop.create_connection() have some overlapping timeouts
+            # that lead to little bit difficulties with working through all addresses returned by getaddrinfo.
+            # We pick one at random here, and rely our own outer loops to handle retries.
+            present_addrs = [
+                gai_result[4][0]
+                for gai_result in await self.websocket_loop.getaddrinfo(
+                    url_parsed.hostname, 0, type=socket.SOCK_STREAM, proto=socket.IPPROTO_TCP
+                )
+            ]
+            if present_addrs:
+                preferred_host = random.choice(present_addrs)
+            else:
+                # We couldn't resolve a suitable name, fallback to async.loop.create_connection() name handling
+                preferred_host = url_parsed.hostname
 
         ws_compr = None if self.websocket_compression == WebsocketCompression.none else str(self.websocket_compression)
-        return await websockets.connect(  # pylint:disable=no-member
+        return await websockets.client.connect(
             self.websocket_uri,
+            host=preferred_host,
             ssl=ssl_context,
             compression=ws_compr,
             extra_headers=headers,