@Override
    protected ConfigWatcherRegister initConfigReader() throws ModuleStartException {
        final String apolloCluster = settings.getApolloCluster();

        if (!Strings.isNullOrEmpty(apolloCluster)) {
            System.setProperty("apollo.cluster", apolloCluster);
        }

        final String apolloMeta = settings.getApolloMeta();

        if (!Strings.isNullOrEmpty(apolloMeta)) {
            System.setProperty("apollo.meta", apolloMeta);
        }

        final String appId = settings.getAppId();

        if (!Strings.isNullOrEmpty(appId)) {
            System.setProperty("app.id", appId);
        }

        final String env = settings.getApolloEnv();

        if (!Strings.isNullOrEmpty(env)) {
            System.setProperty("env", env);
        }

        return new ApolloConfigWatcherRegister(settings);
    }
Get configuration from Apollo configuration center.
oap-server/server-configuration/configuration-apollo/src/main/java/org/apache/skywalking/oap/server/configuration/apollo/ApolloConfigurationProvider.java