public List<Endpoint> findEndpoint(final String keyword, final String serviceId,
                                       final int limit, final Duration duration) throws IOException {
        return getMetadataQueryDAO().findEndpoint(keyword, serviceId, limit, duration)
                                    .stream().distinct().collect(Collectors.toList());
    }
@return all services, key is service id, value is services with different layers.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/query/MetadataQueryService.java