Map eviction, time-to-live and max-idle

[Mikael Ståldal]

If you use IMap.set(K key, V value, long ttl, TimeUnit timeunit), will the entry be evicted

a) X seconds after first put into the map, or 

b) X seconds after last updated?

If (a), is there any way to get the (b) behavior?

What about time-to-live and max-idle in map-config? The documentation is slightly vague:

time-to-live: Maximum time in seconds for each entry to stay in the map. If it is not 0, entries that are older than and not updated for this time are evicted automatically. Valid values are integers between 0 and Integer.MAX VALUE. Default value is 0 and it means infinite. Moreover, if it is not 0, entries are evicted regardless of the set eviction-policy.

max-idle-seconds: Maximum time in seconds for each entry to stay idle in the map. Entries that are idle for more than this time are evicted automatically. An entry is idle if no get, put or containsKey is called. Valid values are integers between 0 and Integer.MAX VALUE. Default value is 0 and it means infinite.

I guess this mean that the time-to-live property will evict entries X seconds after last updated? And max-idle will evict entries X seconds after last updated or fetched? (I assume that put(), replace() and set() count as update, and the asynchronous versions as well.)

What will happen if you mix these map-config properties with IMap.set(K key, V value, long ttl, TimeUnit timeunit)?

[Ahmet Mircik]

Hi Mikael,

Behavior is (a).

Max-idle works against last-access-time.

If you mix ttl & max-idle, entry will be evicted according to nearest one in time.

Some more details here: https://github.com/hazelcast/hazelcast/issues/3920

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[Mikael Ståldal]

So how can I get expiration after latest update? Do I have to use IMap.set() and specify longer TTL value for each update operation? What if I want to use IMap.replace()?

[Ahmet Mircik]

If it fits in your use case, using max-idle seems a better option instead of extending TTL in every set operation.

replace updates last-access-time and only affects max-idle expiration, nothing to do with TTL​

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[Mikael Ståldal]

I don't think that map-config is dynamic enough for my use case.

BTW, why are there no variants of replace() with TTL parameters?

[Ahmet Mircik]

Some reasons;

• IMap extends ConcurrentMap
• and seems no issue has been raised from the community so far. Can you always create an issue for it (better with a good reasoning and use cases)? https://github.com/hazelcast/hazelcast/issues

​

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