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 com.att.eelf.configuration.EELFLogger;
28 import com.att.eelf.configuration.EELFManager;
29 import java.util.concurrent.locks.ReentrantLock;
30 import org.onap.appc.rankingframework.RankedAttributesResolver;
32 abstract class AbstractResolver {
34 private static final EELFLogger logger = EELFManager.getInstance().getLogger(AbstractResolver.class);
36 private long interval;
38 private volatile long lastUpdate = 0l;
39 private volatile boolean isUpdateInProgress = false;
40 private volatile RankedAttributesResolver<FlowKey> dgResolver;
42 private final ReentrantLock INIT_LOCK = new ReentrantLock();
44 AbstractResolver(int interval) {
45 this.interval = interval * 1000l;
48 private RankedAttributesResolver<FlowKey> createResolver(String resolverType) {
49 AbstractResolverDataReader reader = ResolverDataReaderFactory.createResolverDataReader(resolverType);
53 private boolean isExpired() {
54 return (System.currentTimeMillis() - lastUpdate) > interval;
57 protected RankedAttributesResolver<FlowKey> resolver(String resolverType) {
60 * In general case, the method implementation is non-blocking. The first
61 * thread that identifies data expiration will be used to refresh it. In
62 * meanwhile, any other thread will get the old instance without waiting
63 * for the updated one. The only exception is the very first time when
64 * previous instance doesn't exist - in such a cases all the threads
65 * will be waiting on INIT_LOCK while one of them initializes the
66 * resolver instance. NOTE: The initialization is intentionally
67 * implemented in lazy manner to make sure the bundle is initialized
68 * properly on startup regardless whether or not the data is correct.
69 * Afterwards, the resolver may be instantiated as many times as needed.
74 if (dgResolver == null) {
76 if (dgResolver != null) {
81 if (!isUpdateInProgress && isExpired()) {
83 boolean doUpgrade = false;
86 if (!isUpdateInProgress) {
87 isUpdateInProgress = true;
94 logger.info("DG resolver configuration data has expired - initiating refresh");
97 RankedAttributesResolver<FlowKey> temp = createResolver(resolverType);
99 lastUpdate = System.currentTimeMillis();
101 logger.info("DG resolver configuration data has been refreshed successfully");
103 isUpdateInProgress = false;
108 if (INIT_LOCK.isHeldByCurrentThread()) {
116 protected abstract FlowKey resolve(final String... args);