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https://issues.apache.org/jira/browse/FLINK-6425?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15999769#comment-15999769
]
ASF GitHub Bot commented on FLINK-6425:
---------------------------------------
Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/3834#discussion_r115139044
--- Diff:
flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java
---
@@ -1473,22 +1481,92 @@ void restore(Collection<KeyedStateHandle>
restoreStateHandles) throws Exception
protected <N, S> ColumnFamilyHandle getColumnFamily(
StateDescriptor<?, S> descriptor, TypeSerializer<N>
namespaceSerializer) throws IOException {
- Tuple2<ColumnFamilyHandle, RegisteredBackendStateMetaInfo<?,
?>> stateInfo =
+ Tuple2<ColumnFamilyHandle,
RegisteredKeyedBackendStateMetaInfo<?, ?>> stateInfo =
kvStateInformation.get(descriptor.getName());
- RegisteredBackendStateMetaInfo<N, S> newMetaInfo = new
RegisteredBackendStateMetaInfo<>(
- descriptor.getType(),
- descriptor.getName(),
- namespaceSerializer,
- descriptor.getSerializer());
+ RegisteredKeyedBackendStateMetaInfo<N, S> newMetaInfo = new
RegisteredKeyedBackendStateMetaInfo<>(
+ descriptor.getType(),
+ descriptor.getName(),
+ namespaceSerializer,
+ descriptor.getSerializer());
if (stateInfo != null) {
- if (newMetaInfo.canRestoreFrom(stateInfo.f1)) {
+ // TODO with eager registration in place, these checks
should be moved to restore()
+
+ RegisteredKeyedBackendStateMetaInfo.Snapshot<N, S>
restoredMetaInfo =
+
restoredKvStateMetaInfos.get(descriptor.getName());
+
+ Preconditions.checkState(
+
newMetaInfo.getName().equals(restoredMetaInfo.getName()),
+ "Incompatible state names. " +
+ "Was [" + restoredMetaInfo.getName() +
"], " +
+ "registered with [" +
newMetaInfo.getName() + "].");
+
+ if
(!newMetaInfo.getStateType().equals(StateDescriptor.Type.UNKNOWN)
+ &&
!restoredMetaInfo.getStateType().equals(StateDescriptor.Type.UNKNOWN)) {
+
+ Preconditions.checkState(
+
newMetaInfo.getStateType().equals(restoredMetaInfo.getStateType()),
+ "Incompatible state types. " +
+ "Was [" +
restoredMetaInfo.getStateType() + "], " +
+ "registered with [" +
newMetaInfo.getStateType() + "].");
+ }
+
+ // check serializer migration strategies to determine
if state migration is required
+
+ boolean requireMigration = false;
+
+ // only check migration strategy if there is a restored
configuration snapshot;
+ // there wouldn't be one if we were restored from an
older version checkpoint,
+ // in which case we can only simply assume that
migration is not required
+
+ if
(restoredMetaInfo.getNamespaceSerializerConfigSnapshot() != null) {
+ MigrationStrategy<N> namespaceMigrationStrategy
= newMetaInfo.getNamespaceSerializer()
+
.getMigrationStrategyFor(restoredMetaInfo.getNamespaceSerializerConfigSnapshot());
+
+ TypeSerializer<N> finalOldNamespaceSerializer;
+ if
(namespaceMigrationStrategy.requireMigration()) {
+ requireMigration = true;
+
+ if
(namespaceMigrationStrategy.getFallbackDeserializer() != null) {
+ finalOldNamespaceSerializer =
namespaceMigrationStrategy.getFallbackDeserializer();
+ } else if
(restoredMetaInfo.getNamespaceSerializer() != null
+ &&
!(restoredMetaInfo.getNamespaceSerializer() instanceof
MigrationNamespaceSerializerProxy)) {
+ finalOldNamespaceSerializer =
restoredMetaInfo.getNamespaceSerializer();
+ } else {
+ throw new RuntimeException(
+ "State migration
required, but there is no available serializer capable of reading previous
namespace.");
+ }
+ }
+ }
+
+ if (restoredMetaInfo.getStateSerializerConfigSnapshot()
!= null) {
--- End diff --
This almost looks like duplicated code from the previous `if`. Maybe we can
create a common helper method to do this and avoid (partial) code duplication.
> Integrate serializer reconfiguration into state restore flow to activate
> serializer upgrades
> --------------------------------------------------------------------------------------------
>
> Key: FLINK-6425
> URL: https://issues.apache.org/jira/browse/FLINK-6425
> Project: Flink
> Issue Type: Sub-task
> Components: State Backends, Checkpointing
> Reporter: Tzu-Li (Gordon) Tai
> Assignee: Tzu-Li (Gordon) Tai
>
> With FLINK-6191, {{TypeSerializer}} will be reconfigurable.
> From the state backends' point of view, serializer reconfiguration doubles as
> a mechanism to determine how serializer upgrades should be handled.
> The general idea is that state checkpoints should contain the following as
> the state's metainfo:
> - the previous serializer
> - snapshot of the previous serializer's configuration
> The upgrade flow is as follows:
> 1. On restore, try to deserialize the previous old serializer.
> Deserialization may fail if a) the serializer no longer exists in classpath,
> or b) the serializer class is not longer valid (i.e., implementation changed
> and resulted in different serialVersionUID). In this case, use a dummy
> serializer as a placeholder. This dummy serializer is currently the
> {{ClassNotFoundProxySerializer}} in the code.
> 2. Deserialize the configuration snapshot of the previous old serializer. The
> configuration snapshot must be successfully deserialized, otherwise the state
> restore fails.
> 3. When we get the new registered serializer for the state (could be a
> completely new serializer, the same serializer with different
> implementations, or the exact same serializer untouched; either way they are
> seen as a new serializer), we use the configuration snapshot of the old
> serializer to reconfigure the new serializer.
> This completes the upgrade of the old serializer. However, depending on the
> result of the upgrade, state conversion needs to take place (for now, if
> state conversion is required, we just fail the job as this functionality
> isn't available yet). The results could be:
> - Compatible: restore success + serializer upgraded.
> - Compatible, but serialization schema changed: serializer upgraded but
> requires state conversion, without the requirement that the old serializer
> needs to be present.
> - Incompatible: serializer upgraded requires state conversion, but requires
> the old serializer to be present (i.e., can not be the dummy
> {{ClassNotFoundProxySerializer}}).
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