[GitHub] [flink] masteryhx commented on a diff in pull request #19679: [FLINK-23143][state/changelog] Support state migration for ChangelogS…

[GitBox <gi...@apache.org>]

masteryhx commented on code in PR #19679:
URL: https://github.com/apache/flink/pull/19679#discussion_r902140260


##########
flink-state-backends/flink-statebackend-changelog/src/main/java/org/apache/flink/state/changelog/restore/ChangelogRestoreTarget.java:
##########
@@ -21,52 +21,143 @@
 import org.apache.flink.api.common.state.State;
 import org.apache.flink.api.common.state.StateDescriptor;
 import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.runtime.state.AbstractKeyedStateBackend;
 import org.apache.flink.runtime.state.CheckpointableKeyedStateBackend;
 import org.apache.flink.runtime.state.KeyGroupRange;
 import org.apache.flink.runtime.state.KeyGroupedInternalPriorityQueue;
 import org.apache.flink.runtime.state.Keyed;
-import org.apache.flink.runtime.state.KeyedStateBackend;
 import org.apache.flink.runtime.state.PriorityComparable;
-import org.apache.flink.runtime.state.PriorityQueueSetFactory;
 import org.apache.flink.runtime.state.heap.HeapPriorityQueueElement;
+import org.apache.flink.runtime.state.internal.InternalKvState;
+import org.apache.flink.runtime.state.metainfo.StateMetaInfoSnapshot;
 import org.apache.flink.runtime.state.metainfo.StateMetaInfoSnapshot.BackendStateType;
+import org.apache.flink.state.changelog.ChangelogKeyGroupedPriorityQueue;
 import org.apache.flink.state.changelog.ChangelogState;
+import org.apache.flink.state.changelog.ChangelogStateFactory;
+import org.apache.flink.state.changelog.KvStateChangeLogger;
+import org.apache.flink.state.changelog.StateChangeLogger;
 
 import javax.annotation.Nonnull;
 
 /** Maintains metadata operation related to Changelog recovery. */
 @Internal
-public interface ChangelogRestoreTarget<K> {
+public abstract class ChangelogRestoreTarget<K> {
+
+    protected final AbstractKeyedStateBackend<K> keyedStateBackend;
+
+    protected final ChangelogStateFactory changelogStateFactory;
+
+    protected final FunctionDelegationHelper functionDelegationHelper;
+
+    public ChangelogRestoreTarget(
+            AbstractKeyedStateBackend<K> keyedStateBackend,
+            ChangelogStateFactory changelogStateFactory) {
+        this.keyedStateBackend = keyedStateBackend;
+        this.changelogStateFactory = changelogStateFactory;
+        this.functionDelegationHelper = new FunctionDelegationHelper();
+    }
 
     /** Returns the key groups which this restore procedure covers. */
-    KeyGroupRange getKeyGroupRange();
+    public KeyGroupRange getKeyGroupRange() {
+        return keyedStateBackend.getKeyGroupRange();
+    }
+
+    /**
+     * Returns the existing state created by {@link #createKeyedState(TypeSerializer,
+     * StateDescriptor)} or {@link #createPqState(String, TypeSerializer)} in the restore procedure.
+     */
+    public ChangelogState getExistingState(
+            String name, StateMetaInfoSnapshot.BackendStateType type) {
+        return changelogStateFactory.getExistingState(name, type);
+    }
 
     /**
      * Creates a keyed state which could be retrieved by {@link #getExistingState(String,
-     * BackendStateType)} in the restore procedure. The interface comes from {@link
-     * KeyedStateBackend#getOrCreateKeyedState(TypeSerializer, StateDescriptor)}.
+     * BackendStateType)} in the restore procedure.
      */
-    <N, S extends State, V> S createKeyedState(
+    @SuppressWarnings("unchecked")
+    public <N, S extends State, V> S createKeyedState(
             TypeSerializer<N> namespaceSerializer, StateDescriptor<S, V> stateDescriptor)
-            throws Exception;
+            throws Exception {
+        ChangelogState existingState =
+                changelogStateFactory.getExistingState(
+                        stateDescriptor.getName(),
+                        StateMetaInfoSnapshot.BackendStateType.KEY_VALUE);
+        if (existingState == null
+                || !isCompleteCompatible(
+                        (InternalKvState<K, N, V>) existingState,
+                        namespaceSerializer,
+                        stateDescriptor)) {
+            S keyedState =
+                    keyedStateBackend.upgradeKeyedState(namespaceSerializer, stateDescriptor);
+            functionDelegationHelper.addOrUpdate(stateDescriptor);
+            final InternalKvState<K, N, V> kvState = (InternalKvState<K, N, V>) keyedState;
+            return (S)
+                    changelogStateFactory.create(
+                            stateDescriptor,
+                            kvState,
+                            getKvStateChangeLogger(kvState, stateDescriptor),
+                            keyedStateBackend);
+        }
+        return (S) existingState;
+    }
+
+    private <N, S extends State, V> boolean isCompleteCompatible(
+            InternalKvState<K, N, V> existingState,
+            TypeSerializer<N> namespaceSerializer,
+            StateDescriptor<S, V> stateDescriptor) {
+        return isCompleteCompatible(existingState.getNamespaceSerializer(), namespaceSerializer)
+                && isCompleteCompatible(
+                        existingState.getValueSerializer(), stateDescriptor.getSerializer());
+    }
+
+    private <T> boolean isCompleteCompatible(
+            TypeSerializer<T> originalSerializer, TypeSerializer<T> newSerializer) {
+        return originalSerializer.equals(newSerializer);

Review Comment:
   I think `TypeSerializerSchemaCompatibility.Type.COMPATIBLE_AS_IS` is not enough for the case.
   We may also need to update the serializer in RocksDB/HashMap even if the compatibility is `COMPATIBLE_AS_IS` as you could see in [https://github.com/apache/flink/blob/99c2a415e9eeefafacf70762b6f54070f7911ceb/flink-runtime/src/main/java/org/apache/flink/runtime/state/StateSerializerProvider.java#L314](url).
   Using equals because IIUC:
   1. If one serializer is equals the other, they must be `COMPATIBLE_AS_IS`, and no need to update the serializer.
   2. If one serializer `COMPATIBLE_AS_IS` with the other, they are not necessarily equal, and we need to update the serializer.
   
   WDYT?



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