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From tillrohrmann <...@git.apache.org>
Subject [GitHub] flink pull request #2608: [FLINK-4512] [FLIP-10] Add option to persist perio...
Date Tue, 11 Oct 2016 14:16:22 GMT
Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2608#discussion_r82796670
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/savepoint/SavepointStore.java
---
    @@ -18,23 +18,105 @@
     
     package org.apache.flink.runtime.checkpoint.savepoint;
     
    +import org.apache.flink.core.fs.FSDataInputStream;
    +import org.apache.flink.core.fs.FSDataOutputStream;
    +import org.apache.flink.core.fs.FileSystem;
    +import org.apache.flink.core.fs.Path;
    +import org.apache.flink.core.memory.DataInputViewStreamWrapper;
    +import org.apache.flink.util.FileUtils;
    +import org.apache.flink.util.Preconditions;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import java.io.DataInputStream;
    +import java.io.DataOutputStream;
    +import java.io.IOException;
    +
    +import static org.apache.flink.util.Preconditions.checkNotNull;
    +
     /**
    - * Savepoint store used to persist {@link Savepoint} instances.
    + * A file system based savepoint store.
      *
    - * <p>The main implementation is the {@link FsSavepointStore}. We also have the
    - * {@link HeapSavepointStore} for historical reasons (introduced in Flink 1.0).
    + * <p>Stored savepoints have the following format:
    + * <pre>
    + * MagicNumber SavepointVersion Savepoint
    + *   - MagicNumber => int
    + *   - SavepointVersion => int (returned by Savepoint#getVersion())
    + *   - Savepoint => bytes (serialized via version-specific SavepointSerializer)
    + * </pre>
      */
    -public interface SavepointStore {
    +public class SavepointStore {
    +
    +	private static final Logger LOG = LoggerFactory.getLogger(SavepointStore.class);
    +
    +	/** Magic number for sanity checks against stored savepoints. */
    +	private static final int MAGIC_NUMBER = 0x4960672d;
    +
    +	/** Prefix for savepoint files. */
    +	private static final String prefix = "savepoint-";
     
     	/**
     	 * Stores the savepoint.
     	 *
    +	 * @param targetDirectory Target directory to store savepoint in
     	 * @param savepoint Savepoint to be stored
     	 * @param <T>       Savepoint type
     	 * @return Path of stored savepoint
     	 * @throws Exception Failures during store are forwarded
     	 */
    -	<T extends Savepoint> String storeSavepoint(T savepoint) throws Exception;
    +	public static <T extends Savepoint> String storeSavepoint(
    +			String targetDirectory,
    +			T savepoint) throws IOException {
    +
    +		checkNotNull(targetDirectory, "Target directory");
    +		checkNotNull(savepoint, "Savepoint");
    +
    +		Exception latestException = null;
    +		Path path = null;
    +		FSDataOutputStream fdos = null;
    +
    +		FileSystem fs = null;
    +
    +		// Try to create a FS output stream
    +		for (int attempt = 0; attempt < 10; attempt++) {
    +			path = new Path(targetDirectory, FileUtils.getRandomFilename(prefix));
    +
    +			if (fs == null) {
    +				fs = FileSystem.get(path.toUri());
    +			}
    +
    +			try {
    +				fdos = fs.create(path, false);
    +				break;
    +			} catch (Exception e) {
    +				latestException = e;
    +			}
    +		}
    +
    +		if (fdos == null) {
    +			throw new IOException("Failed to create file output stream at " + path, latestException);
    +		}
    +
    +		boolean success = false;
    +		try (DataOutputStream dos = new DataOutputStream(fdos)) {
    +			// Write header
    +			dos.writeInt(MAGIC_NUMBER);
    +			dos.writeInt(savepoint.getVersion());
    +
    +			// Write savepoint
    +			SavepointSerializer<T> serializer = SavepointSerializers.getSerializer(savepoint);
    +			serializer.serialize(savepoint, dos);
    +			success = true;
    +		} finally {
    +			if (!success && fs.exists(path)) {
    +				if (!fs.delete(path, true)) {
    +					LOG.warn("Failed to delete file " + path + " after failed write.");
    --- End diff --
    
    Placeholder {}


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