presto-resource-group-managers/src/main/java/io/prestosql/plugin/resourcegroups/db/DbResourceGroupConfigurationManager.java/DbResourceGroupConfigurationManager/configureChangedGroups
class DbResourceGroupConfigurationManager:    private synchronized void configureChangedGroups(Set<ResourceGroupIdTemplate> changedSpecs)
    {
        for (ResourceGroupIdTemplate resourceGroupIdTemplate : changedSpecs) {
            for (ResourceGroupId resourceGroupId : configuredGroups(resourceGroupIdTemplate)) {
                synchronized (getRootGroup(resourceGroupId)) {
                    configureGroup(groups.get(resourceGroupId), resourceGroupSpecs.get(resourceGroupIdTemplate));
                }
            }
        }
    }