While looking to the HDFS related changes, I noticed that a new custom
eviction feature was also added related to those changes. Unlike the
already existing CustomExpiry which returns an expiration time for a single
key, this takes an EvictionCriteria that is polled periodically and returns
return a list of keys to evict.
I noticed we currently have no tests for this so I'm not sure if it
actually works or not. Is this something we actually want in geode or
should it get removed? My inclination is to move to the HDFS branch,
asssuming we create one, since it came in with that functionality. And then
not merge it back to develop until there are tests associated with it.
-Dan
/**
* Set custom {@link EvictionCriteria} for the region with start time and
* interval of evictor task to be run in milliseconds, or evict incoming
rows
* in case both start and frequency are specified as zero.
*
* @param criteria
* an {@link EvictionCriteria} to be used for eviction for HDFS
* persistent regions
* @param start
* the start time at which periodic evictor task should be first
* fired to apply the provided {@link EvictionCriteria}; if this
is
* zero then current time is used for the first invocation of
evictor
* @param interval
* the periodic frequency at which to run the evictor task after
the
* initial start; if this is if both start and frequency are zero
* then {@link EvictionCriteria} is applied on incoming
insert/update
* to determine whether it is to be retained
*/
public RegionFactory<K, V> setCustomEvictionAttributes(
EvictionCriteria<K, V> criteria, long start, long interval) {
/**
* Interface implemented by an EVICTION BY CRITERIA of
* {@link CustomEvictionAttributes}. This will be invoked by periodic
evictor
* task that will get the keys to be evicted using this and then destroy
from
* the region to which this is attached.
*
* @author swale
* @since gfxd 1.0
*/
public interface EvictionCriteria<K, V> {
/**
* Get the (key, routing object) of the entries to be evicted from region
* satisfying EVICTION BY CRITERIA at this point of time.
* <p>
* The returned Map.Entry object by the Iterator may be reused internally
so
* caller must extract the key, routing object from the entry on each
* iteration.
*/
Iterator<Map.Entry<K, Object>> getKeysToBeEvicted(long currentMillis,
Region<K, V> region);
/**
* Last moment check if an entry should be evicted or not applying the
* EVICTION BY CRITERIA again under the region entry lock in case the
entry
* has changed after the check in {@link #getKeysToBeEvicted}.
*/
boolean doEvict(EntryEvent<K, V> event);
/**
* Return true if this eviction criteria is equivalent to the other one.
This
* is used to ensure that custom eviction is configured identically on
all the
* nodes of a cluster hosting the region to which this eviction criteria
has
* been attached.
*/
boolean isEquivalent(EvictionCriteria<K, V> other);
}
