com.streamsets.extra.DockerMetadataCache.java Source code

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Here is the source code for com.streamsets.extra.DockerMetadataCache.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 com.streamsets.extra;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.nio.charset.Charset;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class DockerMetadataCache {
    private static final Logger LOG = LoggerFactory.getLogger(DockerMetadataCache.class);
    private final LoadingCache<String, Map> cache;

    private final String basePath;
    private final String filename;

    public DockerMetadataCache(String base, String file) {
        this.basePath = base;
        this.filename = file;
        CacheLoader<String, Map> loader = new CacheLoader<String, Map>() {
            private final ObjectMapper mapper = new ObjectMapper();

            @Override
            public Map load(String key) throws Exception {
                FileSystem fs = FileSystems.getDefault();
                Path path = fs.getPath(basePath, key, filename);
                final String contents = new String(Files.readAllBytes(path), Charset.forName("UTF-8"));
                return mapper.readValue(contents, HashMap.class);
            }
        };

        cache = CacheBuilder.newBuilder().expireAfterAccess(10, TimeUnit.MINUTES).maximumSize(1000).build(loader);
    }

    public Object get(String key) {
        try {
            return cache.get(key);
        } catch (ExecutionException e) {
            LOG.error("Failed to get cached object for key: '{}'", key);
            return null;
        }
    }
}