@Override
        void onResponse(final ClientResponse response) {
            long currentTimeMs = response.receivedTimeMs();
            OffsetFetchResponse fetchResponse = (OffsetFetchResponse) response.responseBody();
            Errors responseError = fetchResponse.groupLevelError(groupId);
            if (responseError != Errors.NONE) {
                onFailure(currentTimeMs, responseError);
                return;
            }
            onSuccess(currentTimeMs, fetchResponse);
        }
Handle OffsetFetch response, including successful and failed.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/CommitRequestManager.java