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3. Google Cloud Datastore

Google Cloud Datastore

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Errors and Error Handling

When a Datastore request is successful, the API will return an HTTP 200 Ok status code along with the requested data in the body of the response.

When a request fails, the Datastore API will return an HTTP 4xx or 5xx status code that generically identifies the failure as well as a JSON response that provides more specific information about the error(s) that caused the failure.

The rest of this page describes the structure of an error, enumerates specific error codes and how to handle them, and shows how to handle errors using the Datastore client libraries.

1. Error Structure
2. Error Codes
3. Error Handling in Client Libraries

Error Structure

{
  "error": {
    "errors": [
     {
       "domain": "global",
       "reason": "INVALID_ARGUMENT",
       "message": "Key path is incomplete: [Person: null]"
     }
    ],
    "code": 400,
    "message": "Key path is incomplete: [Person: null]"
  }
}

Note: The message could change at any time so applications should not depend on the actual message text.

Error Codes

Error Handling in Client Libraries

The following snippet shows how to catch and parse an error using the Datastore client library.

try:
  self.datastore.commit(req)
except datastore.RPCError as e:
  code = e.response.status
  method = e.method
  error = json.loads(e.reason)['error']['errors'][0]
  reason = error['reason']
  message = error['message']
  # ... process error ...

try {
  commitResponse = datastore.commit(commitRequest);
} catch (DatastoreException e) {
  int code = e.getCode();
  String method = e.getMethodName();
  JSONObject json = new JSONObject(new JSONTokener(e.getMessage()));
  JSONObject error = json.getJSONObject("error")
      .getJSONArray("errors")
      .getJSONObject(0);
  String reason = error.getString("reason");
  String message = error.getString("message");
  // ... process error ...
}