eric-maynard commented on code in PR #433: URL: https://github.com/apache/polaris/pull/433#discussion_r1852642029
########## polaris-service/src/main/java/org/apache/polaris/service/persistence/MetadataCacheManager.java: ########## @@ -0,0 +1,143 @@ +/* + * 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.polaris.service.persistence; + +import java.nio.charset.StandardCharsets; +import java.util.function.Supplier; +import org.apache.iceberg.Table; +import org.apache.iceberg.TableMetadata; +import org.apache.iceberg.TableMetadataParser; +import org.apache.iceberg.catalog.TableIdentifier; +import org.apache.polaris.core.PolarisCallContext; +import org.apache.polaris.core.PolarisConfiguration; +import org.apache.polaris.core.entity.PolarisEntity; +import org.apache.polaris.core.entity.PolarisEntitySubType; +import org.apache.polaris.core.entity.TableLikeEntity; +import org.apache.polaris.core.persistence.PolarisMetaStoreManager; +import org.apache.polaris.core.persistence.PolarisResolvedPathWrapper; +import org.apache.polaris.core.persistence.resolver.PolarisResolutionManifestCatalogView; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +public class MetadataCacheManager { + private static final Logger LOGGER = LoggerFactory.getLogger(MetadataCacheManager.class); + + /** + * Load the cached {@link Table} or fall back to `fallback` if one doesn't exist. If the metadata + * is not currently cached, it may be added to the cache. + */ + public static TableMetadata loadTableMetadata( + TableIdentifier tableIdentifier, + long maxBytesToCache, + PolarisCallContext callContext, + PolarisMetaStoreManager metastoreManager, + PolarisResolutionManifestCatalogView resolvedEntityView, + Supplier<TableMetadata> fallback) { + LOGGER.debug(String.format("Loading cached metadata for %s", tableIdentifier)); + PolarisResolvedPathWrapper resolvedEntities = + resolvedEntityView.getResolvedPath(tableIdentifier, PolarisEntitySubType.TABLE); + TableLikeEntity tableLikeEntity = TableLikeEntity.of(resolvedEntities.getRawLeafEntity()); + boolean isCacheValid = + tableLikeEntity.getMetadataCacheLocation() != null + && tableLikeEntity + .getMetadataLocation() + .equals(tableLikeEntity.getMetadataCacheLocation()); + if (isCacheValid) { + LOGGER.debug(String.format("Using cached metadata for %s", tableIdentifier)); + return TableMetadataParser.fromJson(tableLikeEntity.getMetadataCacheContent()); + } else { + TableMetadata metadata = fallback.get(); + PolarisMetaStoreManager.EntityResult cacheResult = + cacheTableMetadata( + tableLikeEntity, + metadata, + maxBytesToCache, + callContext, + metastoreManager, + resolvedEntityView); + if (!cacheResult.isSuccess()) { + LOGGER.debug(String.format("Failed to cache metadata for %s", tableIdentifier)); + } + return metadata; + } + } + + /** + * Attempt to add table metadata to the cache + * + * @return The result of trying to cache the metadata + */ + private static PolarisMetaStoreManager.EntityResult cacheTableMetadata( + TableLikeEntity tableLikeEntity, + TableMetadata metadata, + long maxBytesToCache, + PolarisCallContext callContext, + PolarisMetaStoreManager metaStoreManager, + PolarisResolutionManifestCatalogView resolvedEntityView) { + String json = TableMetadataParser.toJson(metadata); + // We should not reach this method in this case, but check just in case... + if (maxBytesToCache != PolarisConfiguration.METADATA_CACHE_MAX_BYTES_NO_CACHING) { + long sizeInBytes = json.getBytes(StandardCharsets.UTF_8).length; + if (sizeInBytes > maxBytesToCache) { + LOGGER.debug( + String.format( + "Will not cache metadata for %s; metadata is %d bytes and the limit is %d", + tableLikeEntity.getTableIdentifier(), sizeInBytes, maxBytesToCache)); + return new PolarisMetaStoreManager.EntityResult( + PolarisMetaStoreManager.ReturnStatus.SUCCESS, null); + } else { + LOGGER.debug( + String.format("Caching metadata for %s", tableLikeEntity.getTableIdentifier())); + TableLikeEntity newTableLikeEntity = + new TableLikeEntity.Builder(tableLikeEntity) + .setMetadataContent(tableLikeEntity.getMetadataLocation(), json) Review Comment: I think this is probably not a blocker for this initial PR; we can always add another format later on. > Storing JSON uncompressed and as a string Notably, the metastore does exactly this today for properties and internal properties -- This is an automated message from the Apache Git Service. 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