Class FederationAccessManagerWithHierarchicalCache

java.lang.Object

se.liu.ida.hefquin.federation.access.impl.FederationAccessManagerWithCache

se.liu.ida.hefquin.federation.access.impl.FederationAccessManagerWithHierarchicalCache

All Implemented Interfaces:

StatsProvider, FederationAccessManager

public class FederationAccessManagerWithHierarchicalCache
extends FederationAccessManagerWithCache

A federation access manager that uses a hierarchical cache to store federation access results and cardinality estimates.

The cache consists of two cache layers arranged hierarchically. Requests are first looked up in the primary cache layer. If no cached entry is found, the secondary cache layer is consulted. Entries retrieved from the secondary layer are promoted to the primary layer to improve the performance of future lookups.

Both data retrieval requests and cardinality requests are cached. Cache keys are represented by PersistentCacheKey objects, which uniquely identify a request, the targeted federation member, and the type of cached response.

To reduce duplicate request execution, this class stores CompletableFuture instances in the cache whenever possible. If the underlying cache layers preserve the cached futures, concurrent requests for the same data may share both the same future and the same underlying request execution. However, some cache implementations may store serialized or reconstructed representations of cached values rather than the original future instance. In such cases, the degree to which concurrent requests can be coalesced depends on the behavior of the underlying cache layers.

Cache replacement and invalidation behavior are determined by the policies configured for the underlying cache layers.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	FederationAccessManagerWithHierarchicalCache.DefaultHierarchicalMapCachePolicies	Default cache policies for HierarchicalCache.

Nested classes/interfaces inherited from class se.liu.ida.hefquin.federation.access.impl.FederationAccessManagerWithCache

FederationAccessManagerWithCache.Key, FederationAccessManagerWithCache.MyDefaultCachePolicies

Field Summary

Fields

Modifier and Type	Field	Description
protected final HierarchicalCache<PersistentCacheKey,CompletableFuture<? extends DataRetrievalResponse<?>>,PersistentCacheEntry>	cache

Fields inherited from class se.liu.ida.hefquin.federation.access.impl.FederationAccessManagerWithCache

cacheHitsBRTPF, cacheHitsBRTPFCardinality, cacheHitsOther, cacheHitsSPARQL, cacheHitsSPARQLCardinality, cacheHitsTPF, cacheHitsTPFCardinality, cacheMap, cacheRequestsBRTPF, cacheRequestsOther, cacheRequestsSPARQL, cacheRequestsTPF, fedAccMan

Constructor Summary

Constructors

Constructor	Description
FederationAccessManagerWithHierarchicalCache(FederationAccessManager fedAccMan, Cache<PersistentCacheKey,CompletableFuture<? extends DataRetrievalResponse<?>>> l1Cache, Cache<PersistentCacheKey,CompletableFuture<? extends DataRetrievalResponse<?>>> l2Cache)	Creates a federation access manager with a ChronicleMap-backed persistent cache using the given capacity and cache policies.

Method Summary

Modifier and Type	Method	Description
<ReqType extends DataRetrievalRequest, RespType extends DataRetrievalResponse<?>, MemberType extends FederationMember> CompletableFuture<CardinalityResponse>	issueCardinalityRequest(ReqType req, MemberType fm)	Issues a cardinality request for the given request and federation member.
<ReqType extends DataRetrievalRequest, RespType extends DataRetrievalResponse<?>, MemberType extends FederationMember> CompletableFuture<RespType>	issueRequest(ReqType req, MemberType fm)	Issues a request for the given request and federation member.
void	shutdown()	Shuts down all thread pools associated with this federation access manager.

Methods inherited from class se.liu.ida.hefquin.federation.access.impl.FederationAccessManagerWithCache

getStats, resetStats

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

cache

protected final HierarchicalCache<PersistentCacheKey,CompletableFuture<? extends DataRetrievalResponse<?>>,PersistentCacheEntry> cache

Constructor Details

FederationAccessManagerWithHierarchicalCache

public FederationAccessManagerWithHierarchicalCache(FederationAccessManager fedAccMan,
 Cache<PersistentCacheKey,CompletableFuture<? extends DataRetrievalResponse<?>>> l1Cache,
 Cache<PersistentCacheKey,CompletableFuture<? extends DataRetrievalResponse<?>>> l2Cache)
                                             throws IOException

Creates a federation access manager with a ChronicleMap-backed persistent cache using the given capacity and cache policies.

Parameters:

fedAccMan - the wrapped federation access manager

l1Cache -

l2Cache -

Throws:

IOException

Method Details

issueRequest

public <ReqType extends DataRetrievalRequest,
RespType extends DataRetrievalResponse<?>,
MemberType extends FederationMember>
CompletableFuture<RespType> issueRequest(ReqType req,
 MemberType fm)
                                  throws FederationAccessException

Issues a request for the given request and federation member.

Checks the cache first and returns a cached response if available. Otherwise, delegates the request to the wrapped federation access manager and caches the result asynchronously.

Specified by:

issueRequest in interface FederationAccessManager

Overrides:

issueRequest in class FederationAccessManagerWithCache

Parameters:

req - the data retrieval request (TPF, BRTPF, or SPARQL)

fm - the federation member handling the request

Returns:

a CompletableFuture with the response

Throws:

FederationAccessException - if the request fails

IllegalStateException - if the request/member combination is unsupported

issueCardinalityRequest

public <ReqType extends DataRetrievalRequest,
RespType extends DataRetrievalResponse<?>,
MemberType extends FederationMember>
CompletableFuture<CardinalityResponse> issueCardinalityRequest(ReqType req,
 MemberType fm)
                                                        throws FederationAccessException

Issues a cardinality request for the given request and federation member.

Checks the cache first and returns a cached response if available. Otherwise, delegates the request to the wrapped federation access manager and caches the result asynchronously.

Specified by:

issueCardinalityRequest in interface FederationAccessManager

Overrides:

issueCardinalityRequest in class FederationAccessManagerWithCache

Parameters:

req - the data retrieval request (TPF, BRTPF, or SPARQL)

fm - the federation member handling the request

Returns:

a CompletableFuture with the cardinality response

Throws:

FederationAccessException - if the request fails

IllegalStateException - if the request/member combination is unsupported

shutdown

public void shutdown()

Description copied from class: FederationAccessManagerWithCache

Shuts down all thread pools associated with this federation access manager.

Specified by:

shutdown in interface FederationAccessManager

Overrides:

shutdown in class FederationAccessManagerWithCache