service-registry-curator/src/main/java/com/rackspacecloud/client/service_registry/curator/Utils.java
public static String sanitizeTag(String s) {
        // if > 55 chars, assume max entropy is at the end (like a class name).
        if (s.length() > MAX_TAG_LENGTH) {
            s = s.substring(s.length() - MAX_TAG_LENGTH);
        }
        return s;
    }
public static String sanitizeTag(String s) {
        // if > 55 chars, assume max entropy is at the end (like a class name).
        if (s.length() > MAX_TAG_LENGTH) {
            s = s.substring(s.length() - MAX_TAG_LENGTH);
        }
        return s;
    }
1..55 chars. anything goes.