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_r226688632
##########
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.",
+ 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)) {
+
+ iterator.seekToFirst();
+ while (iterator.isValid()) {
+ byte[] serializedValue = iterator.value();
+ byte[] migratedSerializedValue =
rocksDBState.migrateSerializedValue(
+ serializedValue,
+ (TypeSerializer<SV>)
restoredMetaInfoSnapshot.getTypeSerializerConfigSnapshot(StateMetaInfoSnapshot.CommonSerializerKeys.VALUE_SERIALIZER).restoreSerializer(),
+ stateDesc.getSerializer());
+ db.put(stateInfo.f0, iterator.key(),
migratedSerializedValue);
Review comment:
You should insert the values using a `RocksDBWriteBatchWrapper`. This will
result in bulk writes and better performance.
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