fix(http): make the HTTP transport threadsafe

Fix the bug on the `app.lib.http.http_transport.HTTPTransport` class causing the transport to close prematurely when used in concurrent contexts.

app/core/transport.py

@@ -23,7 +23,14 @@
 
 
 class Transport(Disposable, metaclass=ABCMeta):
-    """Represents the flow of data between an IDR Server and this app."""
+    """
+    Represents the flow of data between an IDR Server and this app.
+
+    .. note::
+        It is highly recommended that implementors of this interface make their
+        implementations thread safe as a transport is likely to be used in a
+        concurrent context.
+    """
 
     @abstractmethod
     def fetch_data_source_extracts(

app/lib/transports/http/http_transport.py

@@ -1,4 +1,5 @@
 import logging
+from threading import RLock
 from typing import Any, Mapping, Optional, Sequence
 
 from requests.auth import AuthBase
@@ -53,6 +54,9 @@ class HTTPTransport(Transport):
     An implementation of the :class:`transport <Transport>` interface that uses
     the HTTP protocol for data transmission between an IDR Server and IDR
     client.
+
+    .. note::
+        This implementation is thread safe.
     """
 
     def __init__(
@@ -87,6 +91,9 @@ def __init__(
             }
         )
         self._session.hooks["response"].append(_log_response)
+        self._lock: RLock = RLock()
+        # Mutable state. This properties should be guarded under a lock when
+        # being modified.
         self._auth: AuthBase = _NoAuth()
         self._is_closed: bool = False
 
@@ -96,8 +103,10 @@ def is_disposed(self) -> bool:
 
     def dispose(self) -> None:
         _LOGGER.debug("Closing transport")
-        self._is_closed = True
-        self._session.close()
+        if not self._is_closed:
+            with self._lock:
+                self._is_closed = True
+                self._session.close()
 
     #  FETCH DATA SOURCE EXTRACTS
     # -------------------------------------------------------------------------
@@ -263,15 +272,16 @@ def _make_request(self, request: HTTPRequestParams) -> Response:
             # if the status is among the re-authentication trigger status and
             # if so, re-authenticate and then retry this request.
             if response.status_code in self._api_dialect.auth_trigger_statuses:
-                _LOGGER.debug(
-                    'Encountered an authentication trigger status("%d"), '
-                    "re-authenticating.",
-                    response.status_code,
-                )
-                self._auth = self._authenticate()
-                _LOGGER.debug(
-                    "Re-authentication successful, retrying the request."
-                )
+                with self._lock:
+                    _LOGGER.debug(
+                        'Encountered an authentication trigger status("%d"), '
+                        "re-authenticating.",
+                        response.status_code,
+                    )
+                    self._auth = self._authenticate()
+                    _LOGGER.debug(
+                        "Re-authentication successful, retrying the request."
+                    )
                 # FIXME: This could lead into a stack overflow, revisit this.
                 return self._make_request(request)