DefaultNodeCache.java

/*
 * Copyright 2016 Kevin Herron
 *
 * 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 com.digitalpetri.opcua.sdk.client.nodes;

import java.time.Duration;
import java.util.Collections;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

import com.digitalpetri.opcua.sdk.client.api.nodes.NodeCache;
import com.digitalpetri.opcua.stack.core.AttributeId;
import com.digitalpetri.opcua.stack.core.types.builtin.DataValue;
import com.digitalpetri.opcua.stack.core.types.builtin.NodeId;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheStats;
import com.google.common.collect.Maps;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DefaultNodeCache implements NodeCache {

    private final Logger logger = LoggerFactory.getLogger(getClass());

    private volatile long expireAfterNanos = Duration.ofMinutes(2).toNanos();
    private volatile long maximumSize = 1024;

    private volatile Cache<NodeId, Map<AttributeId, DataValue>> cache = buildCache();

    @Override
    @SuppressWarnings("unchecked")
    public Optional<DataValue> getAttribute(NodeId nodeId, AttributeId attributeId) {
        Map<AttributeId, DataValue> attributes = cache.getIfPresent(nodeId);

        try {
            return attributes == null ?
                    Optional.empty() :
                    Optional.ofNullable(attributes.get(attributeId));
        } catch (ClassCastException e) {
            return Optional.empty();
        }
    }

    @Override
    public void putAttribute(NodeId nodeId, AttributeId attributeId, DataValue attribute) {
        try {
            Map<AttributeId, DataValue> attributes = cache.get(nodeId,
                    () -> Collections.synchronizedMap(Maps.newEnumMap(AttributeId.class)));

            attributes.put(attributeId, attribute);
        } catch (ExecutionException e) {
            logger.error("Error loading value: {}", e.getMessage(), e);
        }
    }

    @Override
    public void invalidate(NodeId nodeId) {
        cache.invalidate(nodeId);
    }

    @Override
    public void invalidate(NodeId nodeId, AttributeId attributeId) {
        Optional.ofNullable(cache.getIfPresent(nodeId))
                .ifPresent(attributes -> attributes.remove(attributeId));
    }

    @Override
    public void invalidateAll() {
        cache.invalidateAll();
    }

    public CacheStats getStats() {
        return cache.stats();
    }

    public synchronized void setExpireAfter(long duration, TimeUnit unit) {
        this.expireAfterNanos = unit.toNanos(duration);

        Cache<NodeId, Map<AttributeId, DataValue>> newCache = buildCache();

        newCache.putAll(cache.asMap());

        cache = newCache;
    }

    public synchronized void setMaximumSize(long maximumSize) {
        this.maximumSize = maximumSize;

        Cache<NodeId, Map<AttributeId, DataValue>> newCache = buildCache();

        newCache.putAll(cache.asMap());

        cache = newCache;
    }

    private Cache<NodeId, Map<AttributeId, DataValue>> buildCache() {
        return CacheBuilder.newBuilder()
                .expireAfterWrite(expireAfterNanos, TimeUnit.NANOSECONDS)
                .maximumSize(maximumSize)
                .recordStats()
                .build();
    }

}