golang-lru
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hashicorp
Implement LRU cache with TTL
This implements LRU with TTL:
-
Each item is added with
lastAccessedTimewhich is used to remove the items once it meets TTL. -
This ensures eventual consistency. Some items may continue to exists until the cleanup routine or GET call cleans it up. Please note that other calls
Contains,Peek,Len, etc. will continue to include the expired item in their result unless otherwise it is removed by either GET or cleanup routine. -
Cleanup on the GET ensures that the user never access the expired item.
Follow up:
- Move the interface from simple LRU to the top level and make sure lru.go and lru_ttl.go implements the interface. Now, that TTL is at the outer level, interface is not required in simplelru.
- Use the testutils in lru_test.go
Signed-off-by: Yuva Shankar [email protected]
Why is lastAccessTime updated only on Add? I assume what you mean that value to do is instead slide the TTL window for expiry, but the variable name makes it sound like it should be updated by Get.
I think that brings up an open question on the fundamental design: is the right behavior that a value should be expired from the cache after it hasn't been accessed for a period of time, or hasn't been updated for a period of time? I think depending on the use-case you could easily want one or the other.
Another issue I see is that the underlying simplelru still has a size cap, so now you have a cache that actually may expire/remove things prior to the given time because there are too many entries. That seems hard to rely on.
