2 * ============LICENSE_START=======================================================
4 * ================================================================================
5 * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
6 * ================================================================================
7 * Copyright (C) 2017 Amdocs
8 * =============================================================================
9 * Licensed under the Apache License, Version 2.0 (the "License");
10 * you may not use this file except in compliance with the License.
11 * You may obtain a copy of the License at
13 * http://www.apache.org/licenses/LICENSE-2.0
15 * Unless required by applicable law or agreed to in writing, software
16 * distributed under the License is distributed on an "AS IS" BASIS,
17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 * See the License for the specific language governing permissions and
19 * limitations under the License.
21 * ECOMP is a trademark and service mark of AT&T Intellectual Property.
22 * ============LICENSE_END=========================================================
25 package org.onap.appc.dg.common.impl;
27 import org.onap.appc.rankingframework.RankedAttributesResolver;
28 import com.att.eelf.configuration.EELFLogger;
29 import com.att.eelf.configuration.EELFManager;
31 import java.util.concurrent.locks.ReentrantLock;
33 abstract class AbstractResolver {
35 private static final EELFLogger logger = EELFManager.getInstance().getLogger(AbstractResolver.class);
37 private long interval;
39 private volatile long lastUpdate = 0l;
40 private volatile boolean isUpdateInProgress = false;
41 private volatile RankedAttributesResolver<FlowKey> dgResolver;
43 private final ReentrantLock INIT_LOCK = new ReentrantLock();
45 AbstractResolver(int interval) {
46 this.interval = interval * 1000l;
49 private RankedAttributesResolver<FlowKey> createResolver(String resolverType) {
50 AbstractResolverDataReader reader = ResolverDataReaderFactory.createResolverDataReader(resolverType);
54 private boolean isExpired() {
55 return (System.currentTimeMillis() - lastUpdate) > interval;
58 protected RankedAttributesResolver<FlowKey> resolver(String resolverType) {
61 * In general case, the method implementation is non-blocking. The first
62 * thread that identifies data expiration will be used to refresh it. In
63 * meanwhile, any other thread will get the old instance without waiting
64 * for the updated one. The only exception is the very first time when
65 * previous instance doesn't exist - in such a cases all the threads
66 * will be waiting on INIT_LOCK while one of them initializes the
67 * resolver instance. NOTE: The initialization is intentionally
68 * implemented in lazy manner to make sure the bundle is initialized
69 * properly on startup regardless whether or not the data is correct.
70 * Afterwards, the resolver may be instantiated as many times as needed.
75 if (dgResolver == null) {
77 if (dgResolver != null) {
82 if (!isUpdateInProgress && isExpired()) {
84 boolean doUpgrade = false;
87 if (!isUpdateInProgress) {
88 isUpdateInProgress = true;
95 logger.info("DG resolver configuration data has expired - initiating refresh");
98 RankedAttributesResolver<FlowKey> temp = createResolver(resolverType);
100 lastUpdate = System.currentTimeMillis();
102 logger.info("DG resolver configuration data has been refreshed successfully");
104 isUpdateInProgress = false;
109 if (INIT_LOCK.isHeldByCurrentThread()) {
116 protected abstract FlowKey resolve(final String...args);