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Common utilities for providers.
/*
* Copyright (c) 2018 Oracle and/or its affiliates. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.helidon.security.providers;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Supplier;
/**
* Generic cache with eviction and max size.
*
* @param type of keys in this cache
* @param type of values in this cache
*/
public final class EvictableCache {
/**
* Number of threads in the scheduled thread pool to evict records.
*/
public static final int EVICT_THREAD_COUNT = 1;
/**
* Default timeout of records in minutes (inactivity timeout).
*/
public static final long CACHE_TIMEOUT_MINUTES = 60;
/**
* Default eviction period in minutes (how often to evict records).
*/
public static final long CACHE_EVICT_PERIOD_MINUTES = 5;
/**
* Default eviction delay in minutes (how long to wait after the cache is started).
*/
public static final long CACHE_EVICT_DELAY_MINUTES = 1;
/**
* Maximal number of records in the cache.
* If the cache is full, no caching is done and the supplier of value is called for every uncached value.
*/
public static final long CACHE_MAX_SIZE = 100_000;
/**
* Parameter to {@link ConcurrentHashMap#forEachKey(long, Consumer)} used for eviction.
*/
public static final long EVICT_PARALLELISM_THRESHOLD = 10000;
private static final ScheduledThreadPoolExecutor EXECUTOR;
static {
ThreadFactory jf = new ThreadFactory() {
private final AtomicInteger counter = new AtomicInteger(1);
@Override
public Thread newThread(Runnable r) {
return new Thread(r, getClass().getSimpleName() + "-cachePurge_" + counter.getAndIncrement());
}
};
EXECUTOR = new ScheduledThreadPoolExecutor(EVICT_THREAD_COUNT, jf);
}
private final ConcurrentHashMap> cacheMap = new ConcurrentHashMap<>();
private final long cacheTimoutNanos;
private final long cacheMaxSize;
private final long evictParallelismThreshold;
private final ScheduledFuture evictionFuture;
private final BiFunction evictor;
private EvictableCache(Builder builder) {
cacheMaxSize = builder.cacheMaxSize;
cacheTimoutNanos = TimeUnit.NANOSECONDS.convert(builder.cacheTimeout, builder.cacheTimeoutUnit);
evictParallelismThreshold = builder.parallelismThreshold;
evictor = builder.evictor;
evictionFuture = EXECUTOR.scheduleAtFixedRate(
this::evict,
builder.cacheEvictDelay,
builder.cacheEvictPeriod,
builder.cacheEvictTimeUnit);
EXECUTOR.setRemoveOnCancelPolicy(true);
}
/**
* Create a new builder for a cache.
*
* @param type of keys in the cache
* @param type of values in the cache
* @return a builder to build the cache
*/
public static Builder builder() {
return new Builder<>();
}
/**
* Create a new cache with default values.
*
* @param type of keys in the cache
* @param type of values in the cache
* @return new cache built with default values
*/
public static EvictableCache create() {
Builder builder = builder();
return builder.build();
}
void evict() {
cacheMap.forEachKey(evictParallelismThreshold, key -> cacheMap.compute(key, (key1, cacheRecord) -> {
if ((null == cacheRecord) || evictor.apply(cacheRecord.getKey(), cacheRecord.getValue())) {
return null;
} else {
if (cacheRecord.isValid(cacheTimoutNanos)) {
return cacheRecord;
} else {
return null;
}
}
}));
}
/**
* Remove a key from the cache. Return the value if it was cached and valid.
*
* @param key key to remove
* @return value if it was removed and valid, empty otherwise
*/
public Optional remove(K key) {
CacheRecord removed = cacheMap.remove(key);
if (null == removed) {
return Optional.empty();
}
return validate(removed).map(CacheRecord::getValue);
}
/**
* Get current cached value if valid.
*
* @param key key to use
* @return current value in the cache or empty if not present (or invalid)
*/
public Optional get(K key) {
return getRecord(key).flatMap(this::validate).map(CacheRecord::getValue);
}
private Optional> validate(CacheRecord record) {
if (record.isValid(cacheTimoutNanos) && !evictor.apply(record.getKey(), record.getValue())) {
return Optional.of(record);
}
cacheMap.remove(record.key);
return Optional.empty();
}
/**
* Current size of the cache.
* As this cache is using {@link ConcurrentHashMap} as backing store, be aware that this value is not
* guaranteed to be consistent, as puts and removed may be happening in parallel.
*
* @return current size of the cache (including valid and invalid - not yet evicted - values)
*/
public int size() {
return cacheMap.size();
}
/**
* Either return a cached value or compute it and cache it.
*
* @param key key to check/insert value for
* @param valueSupplier supplier called if the value is not yet cached, or is invalid
* @return current value from the cache, or computed value from the supplier
*/
public Optional computeValue(K key, Supplier> valueSupplier) {
try {
return doComputeValue(key, valueSupplier);
} catch (CacheFullException e) {
return valueSupplier.get();
}
}
/**
* Close this cache.
* Cancels eviction future and clears the cache.
*/
public void close() {
evictionFuture.cancel(true);
cacheMap.clear();
}
private Optional doComputeValue(K key, Supplier> valueSupplier) {
CacheRecord record = cacheMap.compute(key, (s, cacheRecord) -> {
if ((null != cacheRecord) && cacheRecord.isValid(cacheTimoutNanos)) {
cacheRecord.accessed();
return cacheRecord;
}
if (cacheMap.size() >= cacheMaxSize) {
throw new CacheFullException();
}
return valueSupplier.get()
.map(v -> new CacheRecord<>(key, v))
.orElse(null);
});
if (null == record) {
return Optional.empty();
} else {
return Optional.of(record.value);
}
}
private Optional> getRecord(K key) {
return Optional.ofNullable(cacheMap.get(key));
}
private static final class CacheRecord {
private final K key;
private final V value;
private volatile long lastAccess = System.nanoTime();
private CacheRecord(K key, V value) {
this.key = key;
this.value = value;
}
private void accessed() {
lastAccess = System.nanoTime();
}
private boolean isValid(long timeoutNanos) {
return (System.nanoTime() - lastAccess) < timeoutNanos;
}
private K getKey() {
return key;
}
private V getValue() {
return value;
}
}
/**
* Builder to create instances of {@link EvictableCache}.
*
* @param types of keys used in the cache
* @param types of values used in the cache
*/
public static class Builder {
private long cacheTimeout = CACHE_TIMEOUT_MINUTES;
private long cacheMaxSize = CACHE_MAX_SIZE;
private TimeUnit cacheTimeoutUnit = TimeUnit.MINUTES;
private long cacheEvictDelay = CACHE_EVICT_DELAY_MINUTES;
private long cacheEvictPeriod = CACHE_EVICT_PERIOD_MINUTES;
private TimeUnit cacheEvictTimeUnit = TimeUnit.MINUTES;
private long parallelismThreshold = EVICT_PARALLELISM_THRESHOLD;
private BiFunction evictor = (key, value) -> false;
/**
* Build a new instance of the cache configured from this builder.
*
* @param types of keys used in the cache
* @param types of values used in the cache
* @return new cache instance
*/
@SuppressWarnings("unchecked")
public EvictableCache build() {
return new EvictableCache(this);
}
/**
* Configure record timeout since last modification.
*
* @param timeout timeout value
* @param timeoutUnit timeout unit
* @return updated builder instance
*/
public Builder timeout(long timeout, TimeUnit timeoutUnit) {
this.cacheTimeout = timeout;
this.cacheTimeoutUnit = timeoutUnit;
return this;
}
/**
* Configure maximal cache size.
*
* @param cacheMaxSize maximal number of records to store in the cache
* @return updated builder instance
*/
public Builder maxSize(long cacheMaxSize) {
this.cacheMaxSize = cacheMaxSize;
return this;
}
/**
* Configure eviction scheduling.
*
* @param evictDelay delay from the creation of the cache to first eviction
* @param evictPeriod how often to evict records
* @param evictTimeUnit time unit to use for these values
* @return updated builder instance
*/
public Builder evictSchedule(long evictDelay, long evictPeriod, TimeUnit evictTimeUnit) {
this.cacheEvictDelay = evictDelay;
this.cacheEvictPeriod = evictPeriod;
this.cacheEvictTimeUnit = evictTimeUnit;
return this;
}
/**
* Configure parallelism threshold.
*
* @param parallelismThreshold see {@link ConcurrentHashMap#forEachKey(long, Consumer)}
* @return updated builder instance
*/
public Builder parallelismThreshold(long parallelismThreshold) {
this.parallelismThreshold = parallelismThreshold;
return this;
}
/**
* Configure evictor to check if a records is still valid.
* This should be a fast way to check, as it is happening in a {@link ConcurrentHashMap#forEachKey(long, Consumer)}.
* This is also called during all get and remove operations to only return valid records.
*
* @param evictor evictor to use, return {@code true} for records that should be evicted, {@code false} for records
* that should stay in cache
* @return updated builder instance
*/
public Builder evictor(BiFunction evictor) {
this.evictor = evictor;
return this;
}
}
private static final class CacheFullException extends RuntimeException {
private CacheFullException() {
}
}
}
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