TokenCache.java

package com.rackspacecloud.blueflood.cache;

import com.codahale.metrics.Gauge;
import com.codahale.metrics.MetricRegistry;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.rackspacecloud.blueflood.types.Token;
import com.rackspacecloud.blueflood.utils.Metrics;

import java.util.concurrent.TimeUnit;

public class TokenCache {

    // this collection is used to reduce the number of tokens that get written.
    // Simply, if a token has been seen within the last 10 minutes, don't bother.
    private final Cache<String, Boolean> insertedTokens;

    private static TokenCache instance = new TokenCache(10, TimeUnit.MINUTES,
                                                        3, TimeUnit.DAYS);


    static {
        Metrics.getRegistry().register(MetricRegistry.name(TokenCache.class, "Current Tokens Count"),
                (Gauge<Long>) instance::getCurrentLocatorCount);
    }

    public static TokenCache getInstance() {
        return instance;
    }

    protected TokenCache(long expireAfterAccessDuration, TimeUnit expireAfterAccessTimeUnit,
                         long expireAfterWriteDuration, TimeUnit expireAfterWriteTimeUnit) {

        insertedTokens =
                CacheBuilder.newBuilder()
                        .expireAfterAccess(expireAfterAccessDuration, expireAfterAccessTimeUnit)
                        .expireAfterWrite(expireAfterWriteDuration, expireAfterWriteTimeUnit)
                        .concurrencyLevel(16)
                        .build();
    }

    @VisibleForTesting
    public static TokenCache getInstance(long expireAfterAccessDuration, TimeUnit expireAfterAccessTimeUnit,
                                           long expireAfterWriteDuration, TimeUnit expireAfterWriteTimeUnit) {

        return new TokenCache(expireAfterAccessDuration, expireAfterAccessTimeUnit,
                                expireAfterWriteDuration, expireAfterWriteTimeUnit);
    }

    public long getCurrentLocatorCount() {
        return insertedTokens.size();
    }

    /**
     * Checks if token is recently inserted
     *
     */
    public synchronized boolean isTokenCurrent(Token token) {
        return insertedTokens.getIfPresent(token.getId()) != null;
    }

    /**
     * Marks the token as recently inserted
     */
    public synchronized void setTokenCurrent(Token token) {
        insertedTokens.put(token.getId(), Boolean.TRUE);
    }

    @VisibleForTesting
    public synchronized void resetCache() {
        insertedTokens.invalidateAll();
    }

}