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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9377) Remove writing serializers as part of the checkpoint meta information
Date Mon, 08 Oct 2018 11:11:01 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9377?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16641663#comment-16641663
] 

ASF GitHub Bot commented on FLINK-9377:
---------------------------------------

dawidwys commented on a change in pull request #6711: [FLINK-9377] [core, state backends]
Remove serializers from checkpoints
URL: https://github.com/apache/flink/pull/6711#discussion_r223302936
 
 

 ##########
 File path: flink-core/src/main/java/org/apache/flink/api/common/typeutils/TypeSerializer.java
 ##########
 @@ -215,5 +216,32 @@
 	 *
 	 * @return the determined compatibility result (cannot be {@code null}).
 	 */
-	public abstract CompatibilityResult<T> ensureCompatibility(TypeSerializerConfigSnapshot
configSnapshot);
+	@Deprecated
+	public CompatibilityResult<T> ensureCompatibility(TypeSerializerConfigSnapshot<?>
configSnapshot) {
+		throw new IllegalStateException(
+			"Seems like that you are still using TypeSerializerConfigSnapshot; if so, this method
must be implemented. " +
+				"Once you change to directly use TypeSerializerSnapshot, then you can safely remove the
implementation " +
+				"of this method.");
+	}
+
+	@Internal
+	public final CompatibilityResult<T> ensureCompatibility(TypeSerializerSnapshot<?>
configSnapshot) {
+		if (configSnapshot instanceof TypeSerializerConfigSnapshot) {
+			return ensureCompatibility((TypeSerializerConfigSnapshot<?>) configSnapshot);
+		} else {
+			@SuppressWarnings("unchecked")
+			TypeSerializerSnapshot<T> casted = (TypeSerializerSnapshot<T>) configSnapshot;
+
+			TypeSerializerSchemaCompatibility<T, ? extends TypeSerializer<T>> compat =
casted.resolveSchemaCompatibility(this);
+			if (compat.isCompatibleAsIs()) {
+				return CompatibilityResult.compatible();
+			} else if (compat.isCompatibleAfterMigration()) {
+				return CompatibilityResult.requiresMigration();
+			} else if (compat.isIncompatible()) {
+				throw new IllegalStateException("The new serializer is incompatible.");
+			} else {
+				throw new IllegalStateException("Guard for future.");
 
 Review comment:
   Maybe let's change the message to a bit more meaningful. I know it should not happen, but
better be safe. How about something like: "Corrupted schema compatibility. This is a bug,
please file a JIRA."?

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> Remove writing serializers as part of the checkpoint meta information
> ---------------------------------------------------------------------
>
>                 Key: FLINK-9377
>                 URL: https://issues.apache.org/jira/browse/FLINK-9377
>             Project: Flink
>          Issue Type: Sub-task
>          Components: State Backends, Checkpointing
>            Reporter: Tzu-Li (Gordon) Tai
>            Assignee: Tzu-Li (Gordon) Tai
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 1.7.0
>
>
> When writing meta information of a state in savepoints, we currently write both the state
serializer as well as the state serializer's configuration snapshot.
> Writing both is actually redundant, as most of the time they have identical information.
>  Moreover, the fact that we use Java serialization to write the serializer and rely on
it to be re-readable on the restore run, already poses problems for serializers such as the
{{AvroSerializer}} (see discussion in FLINK-9202) to perform even a compatible upgrade.
> The proposal here is to leave only the config snapshot as meta information, and use that
as the single source of truth of information about the schema of serialized state.
>  The config snapshot should be treated as a factory (or provided to a factory) to re-create
serializers capable of reading old, serialized state.



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