Timeout for connecting to the Azure app for cron job

src/azure_mail/get_token.py

@@ -0,0 +1,6 @@
+"""Get the app access token for Azure Mail API."""
+
+from azure_mail.main import _get_app_access_token
+
+if __name__ == "__main__":
+    token = _get_app_access_token()  # print(json.dumps(token))

src/azure_mail/main.py

@@ -1,10 +1,13 @@
 """Create an email to send with an Azure app."""
 
 import atexit
-import concurrent.futures
 import datetime
+import json
 import os
 import pathlib
+import subprocess
+import sys
+from concurrent.futures import ThreadPoolExecutor
 
 import dateutil.parser
 import exchangelib
@@ -42,6 +45,16 @@ def _check_or_set_up_cache() -> msal.SerializableTokenCache:
     return cache
 
 
+def initialise_app(
+    client_id: str, authority: str, token_cache: msal.SerializableTokenCache
+) -> msal.PublicClientApplication:
+    return msal.PublicClientApplication(
+        client_id,
+        authority=authority,
+        token_cache=token_cache,
+    )
+
+
 def _get_app_access_token() -> dict:
     """
     Acquire an access token for the Azure app through the MSAL library.
@@ -52,11 +65,25 @@ def _get_app_access_token() -> dict:
 
     """
     authority = "https://login.microsoftonline.com/" + os.environ["TENANT_ID"]
-    global_token_cache = _check_or_set_up_cache()
-    app = msal.PublicClientApplication(
+
+    def check_cache() -> msal.SerializableTokenCache:
+        global_token_cache = _check_or_set_up_cache()
+        if not global_token_cache.has_state_changed:
+            return global_token_cache
+        return None
+
+    with ThreadPoolExecutor() as executor:
+        future = executor.submit(check_cache)
+        try:
+            global_token_cache = future.result(timeout=10)
+        except ThreadPoolExecutor as err:
+            msg = "Token cache check timed out."
+            raise RuntimeError(msg) from err
+
+    app = initialise_app(
         os.environ["CLIENT_ID"],
-        authority=authority,
-        token_cache=global_token_cache,
+        authority,
+        global_token_cache,
     )
 
     accounts = app.get_accounts(username=os.environ["ACCOUNT"])
@@ -70,11 +97,11 @@ def interactive_auth() -> dict:
                 [os.environ["SCOPE"]], login_hint=os.environ["ACCOUNT"]
             )
 
-        with concurrent.futures.ThreadPoolExecutor() as executor:
+        with ThreadPoolExecutor() as executor:
             future = executor.submit(interactive_auth)
             try:
                 result = future.result(timeout=10)  # Timeout set to 10 seconds
-            except concurrent.futures.TimeoutError as err:
+            except ThreadPoolExecutor as err:
                 msg = "Interactive authentication timed out."
                 raise RuntimeError(msg) from err
 
@@ -114,6 +141,30 @@ def _setup_email_account(
     )
 
 
+def get_token_with_timeout(timeout: int) -> dict:
+    try:
+        # Find get_token.py in the same directory as this file
+        script_path = (pathlib.Path(__file__).parent / "get_token.py").resolve()
+        if not script_path.is_file():
+            message = f"Script not found: {script_path}"
+            raise RuntimeError(message)
+        result = subprocess.run(  # noqa: S603
+            [os.sys.executable, str(script_path)],
+            capture_output=True,
+            text=True,
+            timeout=timeout,
+            check=False,
+        )
+        if result.returncode != 0:
+            message = f"Token script failed: {result.stderr}"
+            raise RuntimeError(message)
+        print("DEBUG: result.stdout =", repr(result.stdout), file=sys.stderr)  # noqa: T201
+        return json.loads(result.stdout)
+    except subprocess.TimeoutExpired as err:
+        message = "Token acquisition timed out."
+        raise RuntimeError(message) from err
+
+
 def create_email_list(
     limit: str,
     recipients: list[str],
@@ -124,7 +175,8 @@ def create_email_list(
     If you wish to send an email using the members of the distribution list, you can
     create a list with [member.mailbox for member in distribution_list.members].
     """
-    access_token = _get_app_access_token()
+    access_token = get_token_with_timeout(timeout=10)
+
     account = _setup_email_account(
         access_token=access_token,
     )