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_r227706517
##########
File path:
flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java
##########
@@ -1389,6 +1381,109 @@ private void copyStateDataHandleData(
return Tuple2.of(stateInfo.f0, newMetaInfo);
}
+ private <N, S extends State, SV> void migrateStateIfNecessary(
+ RegisteredKeyValueStateBackendMetaInfo<N, SV>
newMetaInfo,
+ StateDescriptor<S, SV> stateDesc,
+ TypeSerializer<N> namespaceSerializer,
+ Tuple2<ColumnFamilyHandle, RegisteredStateMetaInfoBase>
stateInfo) throws Exception {
+
+ StateMetaInfoSnapshot restoredMetaInfoSnapshot =
restoredKvStateMetaInfos.get(stateDesc.getName());
+
+ CompatibilityResult<N> namespaceCompatibility =
CompatibilityUtil.resolveCompatibilityResult(
+
restoredMetaInfoSnapshot.getTypeSerializer(StateMetaInfoSnapshot.CommonSerializerKeys.NAMESPACE_SERIALIZER.toString()),
+ null,
+
restoredMetaInfoSnapshot.getTypeSerializerConfigSnapshot(StateMetaInfoSnapshot.CommonSerializerKeys.NAMESPACE_SERIALIZER.toString()),
+ namespaceSerializer);
+
+ CompatibilityResult<SV> stateCompatibility =
RegisteredKeyValueStateBackendMetaInfo
+ .resolveStateCompatibiliity(restoredMetaInfoSnapshot,
stateDesc, newMetaInfo.getStateSerializer());
+
+ 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()) {
+ migrateStateValues(stateDesc, stateInfo,
restoredMetaInfoSnapshot, 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 migrateStateValues(
+ StateDescriptor<S, SV> stateDesc,
+ Tuple2<ColumnFamilyHandle, RegisteredStateMetaInfoBase>
stateInfo,
+ StateMetaInfoSnapshot restoredMetaInfoSnapshot,
+ RegisteredKeyValueStateBackendMetaInfo<N, SV> newMetaInfo)
throws Exception {
+
+ if (stateDesc.getType() == 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's schema, i.e. serialization format, has changed.",
+ stateDesc);
+
+ // we need to get an actual state instance because migration is
different
+ // for different state types. For example, ListState needs to
deal with
+ // individual elements
+ StateFactory stateFactory =
STATE_FACTORIES.get(stateDesc.getClass());
+ if (stateFactory == null) {
+ String message = String.format("State %s is not
supported by %s",
+ stateDesc.getClass(), this.getClass());
+ throw new FlinkRuntimeException(message);
+ }
+ State state = stateFactory.createState(
+ stateDesc,
+ Tuple2.of(stateInfo.f0, newMetaInfo),
+ RocksDBKeyedStateBackend.this);
+ if (!(state instanceof AbstractRocksDBState)) {
+ throw new FlinkRuntimeException(
+ "State should be an AbstractRocksDBState but is
" + state);
+ }
+
+ @SuppressWarnings("unchecked")
+ AbstractRocksDBState<?, ?, SV, S> rocksDBState =
(AbstractRocksDBState<?, ?, SV, S>) state;
+
+ Snapshot rocksDBSnapshot = db.getSnapshot();
+ try (
+ RocksIteratorWrapper iterator = getRocksIterator(db,
stateInfo.f0);
+ RocksDBWriteBatchWrapper batchWriter = new
RocksDBWriteBatchWrapper(db, getWriteOptions())
+ ) {
+ iterator.seekToFirst();
+
+ @SuppressWarnings("unchecked")
+ TypeSerializerSnapshot<SV> priorValueSerializerSnapshot
= (TypeSerializerSnapshot<SV>)
+
Preconditions.checkNotNull(restoredMetaInfoSnapshot.getTypeSerializerConfigSnapshot(StateMetaInfoSnapshot.CommonSerializerKeys.VALUE_SERIALIZER));
+ TypeSerializer<SV> priorValueSerializer =
priorValueSerializerSnapshot.restoreSerializer();
+
+ DataInputDeserializer serializedValueInput = new
DataInputDeserializer();
+ DataOutputSerializer migratedSerializedValueOutput =
new DataOutputSerializer(1);
Review comment:
I would suggest a higher initial size, because we can already forsee that
`1` is not enough for basically any state. This is also a temporary buffer,
created once, so i suggest to think of an intial size between `128` und `1024`.
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