alluxio.client.file.cache

Interface CacheUsage

All Superinterfaces:

CacheUsageView

All Known Implementing Classes:

CacheUsageView.ImmutableCacheUsageView

public interface CacheUsage
extends CacheUsageView

Cache usage.
Granularity A usage object of this interface is associated with a certain granularity, either global, of a cache directory, of a application-defined scope, or of a particular file. Coarse-grained cache usage objects may be partitioned into a finer-grained one, for example the global usage can be partitioned into usages of each cache directory.
Stats The following cache usage stats are reported for the granularity of the object:

• Used: size of pages currently cached
• Available: size of free space, plus size of evictable pages
• Capacity: total capacity

Snapshot Cache usage object does not offer atomic view of their stats. Two subsequent calls to get the same stats may return different results, as the underlying cached contents may have changed between the calls. To get a snapshot of the cache stats, call snapshot() to obtain an immutable view of the cache usage.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	CacheUsage.DirPartition Partition on a particular cache directory.
static class	CacheUsage.FilePartition Partition on a particular file.
static interface	CacheUsage.PartitionDescriptor<T> Partition descriptor.
static class	CacheUsage.ScopePartition Partition on a cache scope.

Nested classes/interfaces inherited from interface alluxio.client.file.cache.CacheUsageView

CacheUsageView.ImmutableCacheUsageView

Method Summary

Modifier and Type	Method and Description
Optional<CacheUsage>	partitionedBy(CacheUsage.PartitionDescriptor<?> partition) Gets a finer-grained view of cache usage.
default CacheUsageView	snapshot() Creates an immutable snapshot of the current cache usage.

Methods inherited from interface alluxio.client.file.cache.CacheUsageView

available, capacity, used

Method Detail

snapshot

default CacheUsageView snapshot()

Creates an immutable snapshot of the current cache usage.

Returns:

the snapshot

partitionedBy

Optional<CacheUsage> partitionedBy(CacheUsage.PartitionDescriptor<?> partition)

Gets a finer-grained view of cache usage.
Example of getting cache usage of a particular file:

 cacheManager.getUsage()
     .flatMap(usage -> usage.partitionedBy(PartitionDescriptor.file(fileId))
     .map(CacheUsage::used)
     .orElse(0)
 

Parameters:

partition - how to partition the cache

Returns:

partitioned view of cache usage, none if this usage object does not support partitioning, or usage info for the specified partition is not found