Close urllib3 pool before swapping the server into the "inactive" list

Author: amotl

src/crate/client/http.py

@@ -568,6 +568,15 @@ def _drop_server(self, server, message):
         """
         Drop server from active list and adds it to the inactive ones.
         """
+
+        # Try to close resource first.
+        try:
+            self.server_pool[server].close()
+        except Exception as ex:
+            logger.warning("When removing server from active pool, "
+                           "resource could not be closed: %s", ex)
+
+        # Apply bookkeeping.
         try:
             self._active_servers.remove(server)
         except ValueError:
@@ -576,7 +585,7 @@ def _drop_server(self, server, message):
             heapq.heappush(self._inactive_servers, (time(), server, message))
             logger.warning("Removed server %s from active pool", server)
 
-        # if this is the last server raise exception, otherwise try next
+        # If this is the last server, raise an exception.
         if not self._active_servers:
             raise ConnectionError(
                 ("No more Servers available, "