fix(vector_stores): return 400 when a MongoDB TLS file cannot be read

tlsCAFile and tlsCertificateKeyFile are how a self-managed deployment presents a
private CA, so they are the options on-prem operators actually set. pymongo opens
those files itself during TLS setup and lets OSError out, which is neither a
PyMongoError nor a ValueError, so it missed every branch of the translator and
litellm.exception_type turned it into a 500 with a traceback in the body. A
mistyped path, or one that exists on the host but not inside the container, is a
routine mistake and has to read as a 400 naming the file.

Matched on the exception carrying a filename so a socket-level OSError still falls
through to the branches that handle it. Verified against a self-managed mongod with
a missing CA file, a CA path that is a directory, and a missing client certificate.

litellm/llms/mongodb/common_utils.py

@@ -267,6 +267,14 @@ def translate_mongo_error(error: Exception, index_name: str, database: str, coll
         )
     if isinstance(error, InvalidOperation):
         return config_error(f"The MongoDB client was already closed or is unusable. Driver detail: {error}")
+    # A tlsCAFile or tlsCertificateKeyFile the process cannot open raises OSError from the TLS setup
+    # rather than a PyMongoError, and those options are how self-managed deployments present a private CA
+    if isinstance(error, OSError) and error.filename:
+        return config_error(
+            f"'{error.filename}', named by a TLS option in mongodb_connection_string, could not be read. "
+            "Check that tlsCAFile and tlsCertificateKeyFile point at files this process can open; inside "
+            f"a container that is the path in the container, not on the host. Driver detail: {error}"
+        )
     # pymongo raises a plain ValueError, not a PyMongoError, for an unusable port, which an unescaped
     # ':' in a password also produces, and which would otherwise reach the caller as a 500
     if isinstance(error, ValueError):

tests/test_litellm/llms/mongodb/vector_stores/test_mongodb_transformation.py

@@ -1362,3 +1362,46 @@ class TestUnescapedCredentialsAreDiagnosed:
 
         assert isinstance(translated, BadRequestError)
         assert "database name in the URI path" in str(translated)
+
+
+class TestUnreadableTlsFilesAreDiagnosed:
+    """A private CA is how self-managed deployments present TLS, so tlsCAFile and
+    tlsCertificateKeyFile are on-prem options in practice. pymongo opens those files itself and
+    lets OSError out, which is not a PyMongoError, so before this they reached the caller as a 500
+    with a traceback. The errors here come from pymongo's real TLS setup."""
+
+    @staticmethod
+    def _real_tls_error(uri):
+        from pymongo import MongoClient
+
+        try:
+            MongoClient(uri, serverSelectionTimeoutMS=1500).admin.command("ping")
+        except Exception as e:
+            return e
+        raise AssertionError(f"expected {uri!r} to fail")
+
+    def _translated(self, uri):
+        return translate_mongo_error(self._real_tls_error(uri), index_name=INDEX, database="db", collection="c")
+
+    @pytest.mark.parametrize(
+        "path",
+        ["/nonexistent-directory-for-tests/ca.pem", "/tmp"],
+    )
+    def test_an_unreadable_ca_file_is_a_400_naming_the_path(self, path):
+        translated = self._translated(f"mongodb://localhost:27717/?tls=true&tlsCAFile={path}")
+
+        assert isinstance(translated, BadRequestError)
+        assert path in str(translated)
+        assert "tlsCAFile" in str(translated)
+
+    def test_an_unreadable_client_certificate_is_a_400_naming_the_path(self):
+        path = "/nonexistent-directory-for-tests/client.pem"
+        translated = self._translated(f"mongodb://localhost:27717/?tls=true&tlsCertificateKeyFile={path}")
+
+        assert isinstance(translated, BadRequestError)
+        assert path in str(translated)
+
+    def test_an_oserror_carrying_no_filename_is_left_for_the_other_branches(self):
+        translated = translate_mongo_error(OSError("socket hung up"), index_name=INDEX, database="db", collection="c")
+
+        assert not isinstance(translated, BadRequestError)