feat(ingest): support __from_env__ special server value (#11569)

metadata-ingestion/src/datahub/cli/config_utils.py

@@ -84,6 +84,13 @@ def _get_config_from_env() -> Tuple[Optional[str], Optional[str]]:
     return url or host, token
 
 
+def require_config_from_env() -> Tuple[str, Optional[str]]:
+    host, token = _get_config_from_env()
+    if host is None:
+        raise MissingConfigError("No GMS host was provided in env variables.")
+    return host, token
+
+
 def load_client_config() -> DatahubClientConfig:
     gms_host_env, gms_token_env = _get_config_from_env()
     if gms_host_env:

metadata-ingestion/src/datahub/emitter/rest_emitter.py

@@ -76,6 +76,12 @@ def __init__(
     ):
         if not gms_server:
             raise ConfigurationError("gms server is required")
+        if gms_server == "__from_env__" and token is None:
+            # HACK: similar to what we do with system auth, we transparently
+            # inject the config in here. Ideally this should be done in the
+            # config loader or by the caller, but it gets the job done for now.
+            gms_server, token = config_utils.require_config_from_env()
+
         self._gms_server = fixup_gms_url(gms_server)
         self._token = token
         self.server_config: Dict[str, Any] = {}