[FSSDK-11898] serialize concurrent cmab service calls #1086
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The cmab service caches the results of a cmab prediction retrieve from the server and returns it for subsequent call. This ensures a consistent value is returned for getDecision() within the cache ttl. However, when there is no cached value, if there is concurrent calls to gertDecision() for same userId and ruleId combination, all of these will cause a call to the server and may potentially return different values. The solution is to run concurrent calls for same userId and ruleId combinations one after another. To achieve this, we put each (userId, ruleId) combination in one of the predefined bucktes by hashing the (userId, ruleId) combination and serialize all calls for that particular hash % (num_buckets).
junaed-optimizely
approved these changes
Oct 6, 2025
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Summary
The cmab service caches the results of a cmab prediction retrieved from the server and returns it for subsequent calls. This ensures a consistent value is returned for getDecision() within the cache ttl. However, when there is no cached value, if there are concurrent calls to gertDecision() for same userId and ruleId combination, all of these will cause a call to the server and may potentially return different values.
The solution is to run concurrent calls for same userId and ruleId combinations one after another. To achieve this, we put each (userId, ruleId) combination in one of the predefined bucktes by hashing the (userId, ruleId) combination and serialize all calls for that particular hash % (num_buckets).
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