private void addQueryService(List<Class> classes) {
        classes.add(TopologyQueryService.class);
        classes.add(MetricsMetadataQueryService.class);
        classes.add(MetricsQueryService.class);
        classes.add(TraceQueryService.class);
        classes.add(LogQueryService.class);
        classes.add(MetadataQueryService.class);
        classes.add(AggregationQueryService.class);
        classes.add(AlarmQueryService.class);
        classes.add(TopNRecordsQueryService.class);
        classes.add(BrowserLogQueryService.class);
        classes.add(EventQueryService.class);
        classes.add(TagAutoCompleteQueryService.class);
        classes.add(RecordQueryService.class);
        classes.add(HierarchyQueryService.class);
        classes.add(TTLStatusQuery.class);
    }
Core module definition. Define all open services to other modules.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/CoreModule.java