com.palantir.atlasdb.impl.TableMetadataCache.java Source code

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Here is the source code for com.palantir.atlasdb.impl.TableMetadataCache.java

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/**
 * Copyright 2015 Palantir Technologies
 *
 * Licensed under the BSD-3 License (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://opensource.org/licenses/BSD-3-Clause
 *
 * 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.palantir.atlasdb.impl;

import java.util.concurrent.TimeUnit;

import javax.annotation.CheckForNull;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.palantir.atlasdb.keyvalue.api.KeyValueService;
import com.palantir.atlasdb.table.description.TableMetadata;

public class TableMetadataCache {
    private final LoadingCache<String, TableMetadata> cache;
    private static final TableMetadata EMPTY = new TableMetadata();

    public TableMetadataCache(final KeyValueService kvs) {
        this.cache = CacheBuilder.newBuilder().expireAfterAccess(15, TimeUnit.MINUTES)
                .build(new CacheLoader<String, TableMetadata>() {
                    @Override
                    public TableMetadata load(String tableName) throws Exception {
                        byte[] rawMetadata = kvs.getMetadataForTable(tableName);
                        if (rawMetadata == null || rawMetadata.length == 0) {
                            return EMPTY;
                        }
                        return TableMetadata.BYTES_HYDRATOR.hydrateFromBytes(rawMetadata);
                    }
                });
    }

    @CheckForNull
    public TableMetadata getMetadata(String tableName) {
        TableMetadata ret = cache.getUnchecked(tableName);
        if (ret == EMPTY) {
            return null;
        }
        return ret;
    }
}