public List<Process> listProcesses(final Duration duration, final String instanceId) throws IOException {
        if (duration.getEndTimeBucket() < duration.getStartTimeBucket()) {
            return Collections.emptyList();
        }
        return getMetadataQueryDAO().listProcesses(instanceId, duration, true);
    }
@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