org.apache.druid.common.aws.LazyFileSessionCredentialsProvider.java Source code

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Here is the source code for org.apache.druid.common.aws.LazyFileSessionCredentialsProvider.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.druid.common.aws;

import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.AWSCredentialsProvider;
import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;

public class LazyFileSessionCredentialsProvider implements AWSCredentialsProvider {
    private final AWSCredentialsConfig config;

    /**
     * The field is declared volatile in order to ensure safe publication of the object
     * in {@link #getUnderlyingProvider()} without worrying about final modifiers
     * on the fields of the created object
     *
     * @see <a href="https://github.com/apache/incubator-druid/pull/6662#discussion_r237013157">
     *     https://github.com/apache/incubator-druid/pull/6662#discussion_r237013157</a>
     */
    @MonotonicNonNull
    private volatile FileSessionCredentialsProvider provider;

    public LazyFileSessionCredentialsProvider(AWSCredentialsConfig config) {
        this.config = config;
    }

    @EnsuresNonNull("provider")
    private FileSessionCredentialsProvider getUnderlyingProvider() {
        FileSessionCredentialsProvider syncedProvider = provider;
        if (syncedProvider == null) {
            synchronized (config) {
                syncedProvider = provider;
                if (syncedProvider == null) {
                    syncedProvider = new FileSessionCredentialsProvider(config.getFileSessionCredentials());
                    provider = syncedProvider;
                }
            }
        }
        return syncedProvider;
    }

    @Override
    public AWSCredentials getCredentials() {
        return getUnderlyingProvider().getCredentials();
    }

    @Override
    public void refresh() {
        getUnderlyingProvider().refresh();
    }
}