apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/environment/DefaultPortalMetaServerProvider.java/DefaultPortalMetaServerProvider/getMetaServerAddress
class DefaultPortalMetaServerProvider:    @Override
    public String getMetaServerAddress(Env targetEnv) {
        String metaServerAddress = domains.get(targetEnv);
        return metaServerAddress == null ? null : metaServerAddress.trim();
    }