[GitHub] flink pull request: Out-of-core state backend for JDBC databases

[tillrohrmann <gi...@git.apache.org>]

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1305#discussion_r46264109
  
    --- Diff: flink-contrib/flink-streaming-contrib/src/main/java/org/apache/flink/contrib/streaming/state/DbStateBackend.java ---
    @@ -0,0 +1,248 @@
    +/*
    + * 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.flink.contrib.streaming.state;
    +
    +import java.io.IOException;
    +import java.io.Serializable;
    +import java.sql.Connection;
    +import java.sql.PreparedStatement;
    +import java.sql.SQLException;
    +import java.util.Random;
    +import java.util.concurrent.Callable;
    +
    +import org.apache.flink.api.common.typeutils.TypeSerializer;
    +import org.apache.flink.runtime.execution.Environment;
    +import org.apache.flink.runtime.state.StateBackend;
    +import org.apache.flink.runtime.state.StateHandle;
    +import org.apache.flink.util.InstantiationUtil;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import static org.apache.flink.contrib.streaming.state.SQLRetrier.retry;
    +
    +/**
    + * {@link StateBackend} for storing checkpoints in JDBC supporting databases.
    + * Key-Value state is stored out-of-core and is lazily fetched using the
    + * {@link LazyDbKvState} implementation. A different backend can also be
    + * provided in the constructor to store the non-partitioned states. A common use
    + * case would be to store the key-value states in the database and store larger
    + * non-partitioned states on a distributed file system.
    + * <p>
    + * This backend implementation also allows the sharding of the checkpointed
    + * states among multiple database instances, which can be enabled by passing
    + * multiple database urls to the {@link DbBackendConfig} instance.
    + * <p>
    + * By default there are multiple tables created in the given databases: 1 table
    + * for non-partitioned checkpoints and 1 table for each key-value state in the
    + * streaming program.
    + * <p>
    + * To control table creation, insert/lookup operations and to provide
    + * compatibility for different SQL implementations, a custom
    + * {@link MySqlAdapter} can be supplied in the {@link DbBackendConfig}.
    + *
    + */
    +public class DbStateBackend extends StateBackend<DbStateBackend> {
    +
    +	private static final long serialVersionUID = 1L;
    +	private static final Logger LOG = LoggerFactory.getLogger(DbStateBackend.class);
    +
    +	private Random rnd;
    +
    +	// ------------------------------------------------------
    +
    +	private Environment env;
    --- End diff --
    
    `env` is not serializable


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