Make sure AtMostOnceBarrier only releases once (or never) #4
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I realized the implementation of
incr(self, key, amount, maximum, ttl)assumes a default value of0if the key does not exist. This means, when the backend (e.g. Redis) loses its contents, we would assume everyAtMostOnceBarriernever ran. To fix this, the key is now created with a value of-1(instead of0) and we only release if by incrementing by1we stay under the maximum of0- which can only be true if the previous value was-1and not with the default of0.I also added some tests to confirm this bug existed and to confirm this PR fixes it.