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https://issues.apache.org/jira/browse/FLINK-9808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16656955#comment-16656955
]
ASF GitHub Bot commented on FLINK-9808:
---------------------------------------
StefanRRichter commented on a change in pull request #6875: [FLINK-9808] [state
backends] Migrate state when necessary in state backends
URL: https://github.com/apache/flink/pull/6875#discussion_r226680634
##########
File path:
flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java
##########
@@ -1389,6 +1388,149 @@ private void copyStateDataHandleData(
return Tuple2.of(stateInfo.f0, newMetaInfo);
}
+ private <N, S extends State, SV>
RegisteredKeyValueStateBackendMetaInfo<N, SV> migrateStateIfNecessary(
+ StateDescriptor<S, SV> stateDesc,
+ TypeSerializer<N> namespaceSerializer,
+ Tuple2<ColumnFamilyHandle, RegisteredStateMetaInfoBase>
stateInfo,
+ @Nullable StateSnapshotTransformer<SV>
snapshotTransformer) throws Exception {
+
+ StateMetaInfoSnapshot restoredMetaInfoSnapshot =
restoredKvStateMetaInfos.get(stateDesc.getName());
+
+ Preconditions.checkState(
+ restoredMetaInfoSnapshot != null,
+ "Requested to check compatibility of a restored
RegisteredKeyedBackendStateMetaInfo," +
+ " but its corresponding restored snapshot
cannot be found.");
+
+
Preconditions.checkState(restoredMetaInfoSnapshot.getBackendStateType()
+ ==
StateMetaInfoSnapshot.BackendStateType.KEY_VALUE,
+ "Incompatible state types. " +
+ "Was [" +
restoredMetaInfoSnapshot.getBackendStateType() + "], " +
+ "registered as [" +
StateMetaInfoSnapshot.BackendStateType.KEY_VALUE + "].");
+
+ Preconditions.checkState(
+ Objects.equals(stateDesc.getName(),
restoredMetaInfoSnapshot.getName()),
+ "Incompatible state names. " +
+ "Was [" + restoredMetaInfoSnapshot.getName() +
"], " +
+ "registered with [" + stateDesc.getName() +
"].");
+
+ final StateDescriptor.Type restoredType =
+ StateDescriptor.Type.valueOf(
+ restoredMetaInfoSnapshot.getOption(
+
StateMetaInfoSnapshot.CommonOptionsKeys.KEYED_STATE_TYPE));
+
+ if (!Objects.equals(stateDesc.getType(),
StateDescriptor.Type.UNKNOWN)
+ && !Objects.equals(restoredType,
StateDescriptor.Type.UNKNOWN)) {
+
+ Preconditions.checkState(
+ stateDesc.getType() == restoredType,
+ "Incompatible key/value state types. " +
+ "Was [" + restoredType + "], " +
+ "registered with [" +
stateDesc.getType() + "].");
+ }
+
+ TypeSerializer<SV> stateSerializer = stateDesc.getSerializer();
+
+ RegisteredKeyValueStateBackendMetaInfo<N, SV> newMetaInfo = new
RegisteredKeyValueStateBackendMetaInfo<>(
+ stateDesc.getType(),
+ stateDesc.getName(),
+ namespaceSerializer,
+ stateSerializer,
+ snapshotTransformer);
+
+ CompatibilityResult<N> namespaceCompatibility =
CompatibilityUtil.resolveCompatibilityResult(
+
restoredMetaInfoSnapshot.getTypeSerializer(StateMetaInfoSnapshot.CommonSerializerKeys.NAMESPACE_SERIALIZER.toString()),
+ null,
+
restoredMetaInfoSnapshot.getTypeSerializerConfigSnapshot(StateMetaInfoSnapshot.CommonSerializerKeys.NAMESPACE_SERIALIZER.toString()),
+ namespaceSerializer);
+
+ CompatibilityResult<SV> stateCompatibility =
CompatibilityUtil.resolveCompatibilityResult(
+
restoredMetaInfoSnapshot.getTypeSerializer(StateMetaInfoSnapshot.CommonSerializerKeys.VALUE_SERIALIZER.toString()),
+ null,
+
restoredMetaInfoSnapshot.getTypeSerializerConfigSnapshot(StateMetaInfoSnapshot.CommonSerializerKeys.VALUE_SERIALIZER.toString()),
+ stateSerializer);
+
+ if (namespaceCompatibility.isRequiresMigration()) {
+ throw new UnsupportedOperationException("The new
namespace serializer requires state migration in order for the job to proceed."
+
+ " However, migration for state namespace
currently isn't supported.");
+ }
+
+ if (stateCompatibility.isRequiresMigration()) {
+ migrateStateValue(stateDesc, stateInfo,
restoredMetaInfoSnapshot, newMetaInfo);
+ } else {
+ newMetaInfo = new
RegisteredKeyValueStateBackendMetaInfo<>(
+ newMetaInfo.getStateType(),
+ newMetaInfo.getName(),
+ newMetaInfo.getNamespaceSerializer(),
+ stateSerializer,
+ snapshotTransformer);
+ }
+
+ stateInfo.f1 = newMetaInfo;
+ return newMetaInfo;
+ }
+
+ /**
+ * Migrate only the state value, that is the "value" that is stored in
RocksDB. We don't migrate
+ * the key here, which is made up of key group, key, namespace and map
key
+ * (in case of MapState).
+ */
+ private <N, S extends State, SV> void migrateStateValue(
+ StateDescriptor<S, SV> stateDesc,
+ Tuple2<ColumnFamilyHandle, RegisteredStateMetaInfoBase>
stateInfo,
+ StateMetaInfoSnapshot restoredMetaInfoSnapshot,
+ RegisteredKeyValueStateBackendMetaInfo<N, SV> newMetaInfo)
throws Exception {
+
+ if (stateDesc.getType().equals(StateDescriptor.Type.MAP)) {
+ throw new StateMigrationException("The new serializer
for a MapState requires state migration in order for the job to proceed." +
+ " However, migration for MapState currently
isn't supported.");
+ }
+
+ LOG.info(
+ "Performing state migration for state {} because the
state serializer changed in an incompatible way.",
Review comment:
Maybe rather important to point out that the serialization format changed?
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> Implement state conversion procedure in state backends
> ------------------------------------------------------
>
> Key: FLINK-9808
> URL: https://issues.apache.org/jira/browse/FLINK-9808
> Project: Flink
> Issue Type: Sub-task
> Components: State Backends, Checkpointing
> Reporter: Tzu-Li (Gordon) Tai
> Assignee: Aljoscha Krettek
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.7.0
>
>
> With FLINK-9377 in place and that config snapshots serve as the single source
> of truth for recreating restore serializers, the next step would be to
> utilize this when performing a full-pass state conversion (i.e., read with
> old / restore serializer, write with new serializer).
> For Flink's heap-based backends, it can be seen that state conversion
> inherently happens, since all state is always deserialized after restore with
> the restore serializer, and written with the new serializer on snapshots.
> For the RocksDB state backend, since state is lazily deserialized, state
> conversion needs to happen for per-registered state on their first access if
> the registered new serializer has a different serialization schema than the
> previous serializer.
> This task should consist of three parts:
> 1. Allow {{CompatibilityResult}} to correctly distinguish between whether the
> new serializer's schema is a) compatible with the serializer as it is, b)
> compatible after the serializer has been reconfigured, or c) incompatible.
> 2. Introduce state conversion procedures in the RocksDB state backend. This
> should occur on the first state access.
> 3. Make sure that all other backends no longer do redundant serializer
> compatibility checks. That is not required because those backends always
> perform full-pass state conversions.
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