java mongodb-仅在范围内设置字段

Question

In mongodb i have a field that must be from 0 to MAX (an integer final variable). every time the value hits MAX it must return to 0. to perform this i tried this (java):

Document document = coll.findOneAndUpdate(
    filter,
    new Document(//update
        "$inc",
        new Document("counter", 1)
     )
);
int count = (document != null) ? document.getInteger("counter") : 0;
if(count >= MAX) {
    count-= MAX;
    coll.updateOne(filter, new Document("$set", new Document("counter", count));
}

the only problem is that this is not synchronized, and can cause the counter to lose some counts if multiple clients access this at the same time. to make this synchronized i must test that count is in range from count to max before setting it, how can i achieve this?

Answer 1

You could perform two requests : reset the counter to 0 of it is equal to MAX. Then increase the counter by one. All this using mongodb mechanism such as findAndModify, which guarantees atomicity !