[Kernel]Generalize the actions after commit(like checkpoint) by intro…

…ducing post commit action to kernel (#4115)

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#### Which Delta project/connector is this regarding?
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- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [X] Kernel
- [ ] Other (fill in here)

## Description

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- Describe what this PR changes.
- Describe why we need the change.
 
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correctly link and close the issue upon merge.
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This PR doesn't make any functional changes, but abstract checkpoint
into post commit action. This is prepared adding more post commit
actions such as CRC write (#4116)
## How was this patch tested?
Existing unit test, manual test using
delta/kernel/examples/run-kernel-examples.py --use-local

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## Does this PR introduce _any_ user-facing changes?

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No

kernel/examples/kernel-examples/src/main/java/io/delta/kernel/examples/CreateTableAndInsertData.java

@@ -17,13 +17,16 @@
 
 import java.io.IOException;
 import java.util.*;
+import java.util.concurrent.CompletableFuture;
 
 import org.apache.commons.cli.Options;
 
 import io.delta.kernel.*;
 import io.delta.kernel.data.FilteredColumnarBatch;
 import io.delta.kernel.data.Row;
 import io.delta.kernel.expressions.Literal;
+import io.delta.kernel.hook.PostCommitHook;
+import io.delta.kernel.hook.PostCommitHook.PostCommitHookType;
 import io.delta.kernel.utils.*;
 import static io.delta.kernel.examples.utils.Utils.parseArgs;
 
@@ -409,11 +412,17 @@ public void insertWithOptionalCheckpoint(String tablePath) throws IOException {
         // for every 10 versions.
         for (int i = 0; i < 12; i++) {
             TransactionCommitResult commitResult = insertDataIntoUnpartitionedTable(tablePath);
-            if (commitResult.isReadyForCheckpoint()) {
+            for(PostCommitHook hook: commitResult.getPostCommitHooks())
                 // Checkpoint the table
-                Table.forPath(engine, tablePath).checkpoint(engine, commitResult.getVersion());
-                didCheckpoint = true;
-            }
+                didCheckpoint = didCheckpoint || CompletableFuture.supplyAsync(() -> {
+                    // run the code async
+                    try{
+                        hook.threadSafeInvoke(engine);
+                    } catch (IOException e) {
+                        return false;
+                    }
+                    return hook.getType().equals(PostCommitHookType.CHECKPOINT);
+                }).join(); // wait async finish.
         }
 
         if (!didCheckpoint) {

kernel/kernel-api/src/main/java/io/delta/kernel/TransactionCommitResult.java

@@ -17,7 +17,9 @@
 
 import io.delta.kernel.annotation.Evolving;
 import io.delta.kernel.engine.Engine;
+import io.delta.kernel.hook.PostCommitHook;
 import io.delta.kernel.utils.CloseableIterable;
+import java.util.List;
 
 /**
  * Contains the result of a successful transaction commit. Returned by {@link
@@ -28,11 +30,11 @@
 @Evolving
 public class TransactionCommitResult {
   private final long version;
-  private final boolean isReadyForCheckpoint;
+  private final List<PostCommitHook> postCommitHooks;
 
-  public TransactionCommitResult(long version, boolean isReadyForCheckpoint) {
+  public TransactionCommitResult(long version, List<PostCommitHook> postCommitHooks) {
     this.version = version;
-    this.isReadyForCheckpoint = isReadyForCheckpoint;
+    this.postCommitHooks = postCommitHooks;
   }
 
   /**
@@ -45,13 +47,19 @@ public long getVersion() {
   }
 
   /**
-   * Is the table ready for checkpoint (i.e. there are enough commits since the last checkpoint)? If
-   * yes the connector can choose to checkpoint as the version the transaction is committed as using
-   * {@link Table#checkpoint(Engine, long)}
+   * Operations for connector to trigger post-commit.
    *
-   * @return Is the table ready for checkpointing?
+   * <p>Usage:
+   *
+   * <ul>
+   *   <li>Async: Call {@link PostCommitHook#threadSafeInvoke(Engine)} in separate thread.
+   *   <li>Sync: Direct call {@link PostCommitHook#threadSafeInvoke(Engine)} and block until
+   *       operation ends.
+   * </ul>
+   *
+   * @return list of post-commit operations
    */
-  public boolean isReadyForCheckpoint() {
-    return isReadyForCheckpoint;
+  public List<PostCommitHook> getPostCommitHooks() {
+    return postCommitHooks;
   }
 }

kernel/kernel-api/src/main/java/io/delta/kernel/hook/PostCommitHook.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (2025) The Delta Lake Project Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.delta.kernel.hook;
+
+import io.delta.kernel.engine.Engine;
+import java.io.IOException;
+
+/**
+ * A hook for executing operation after a transaction commit. Hooks are added in the Transaction and
+ * engine need to invoke the hook explicitly for executing the operation. Supported operations are
+ * listed in {@link PostCommitHookType}.
+ */
+public interface PostCommitHook {
+
+  enum PostCommitHookType {
+    /**
+     * Writes a new checkpoint at the version committed by the transaction. This hook is present
+     * when the table is ready for checkpoint according to its configured checkpoint interval. To
+     * perform this operation, reading previous checkpoint + logs is required to construct a new
+     * checkpoint, with latency scaling based on log size (typically seconds to minutes).
+     */
+    CHECKPOINT
+  }
+
+  /** Invokes the post commit operation whose implementation must be thread safe. */
+  void threadSafeInvoke(Engine engine) throws IOException;
+
+  PostCommitHookType getType();
+}

kernel/kernel-api/src/main/java/io/delta/kernel/internal/TransactionImpl.java

@@ -27,9 +27,11 @@
 import io.delta.kernel.engine.Engine;
 import io.delta.kernel.exceptions.ConcurrentWriteException;
 import io.delta.kernel.expressions.Column;
+import io.delta.kernel.hook.PostCommitHook;
 import io.delta.kernel.internal.actions.*;
 import io.delta.kernel.internal.data.TransactionStateRow;
 import io.delta.kernel.internal.fs.Path;
+import io.delta.kernel.internal.hook.CheckpointHook;
 import io.delta.kernel.internal.metrics.TransactionMetrics;
 import io.delta.kernel.internal.metrics.TransactionReportImpl;
 import io.delta.kernel.internal.replay.ConflictChecker;
@@ -354,7 +356,12 @@ private TransactionCommitResult doCommit(
           "Write file actions to JSON log file `%s`",
           FileNames.deltaFile(logPath, commitAsVersion));
 
-      return new TransactionCommitResult(commitAsVersion, isReadyForCheckpoint(commitAsVersion));
+      List<PostCommitHook> postCommitHooks = new ArrayList<>();
+      if (isReadyForCheckpoint(commitAsVersion)) {
+        postCommitHooks.add(new CheckpointHook(dataPath, commitAsVersion));
+      }
+
+      return new TransactionCommitResult(commitAsVersion, postCommitHooks);
     } catch (FileAlreadyExistsException e) {
       throw e;
     } catch (IOException ioe) {

kernel/kernel-api/src/main/java/io/delta/kernel/internal/hook/CheckpointHook.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (2025) The Delta Lake Project Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.delta.kernel.internal.hook;
+
+import io.delta.kernel.Table;
+import io.delta.kernel.engine.Engine;
+import io.delta.kernel.hook.PostCommitHook;
+import io.delta.kernel.internal.fs.Path;
+import java.io.IOException;
+
+/** Write a new checkpoint at the version committed by the txn. */
+public class CheckpointHook implements PostCommitHook {
+
+  private final Path tablePath;
+  private final long checkpointVersion;
+
+  public CheckpointHook(Path tablePath, long checkpointVersion) {
+    this.tablePath = tablePath;
+    this.checkpointVersion = checkpointVersion;
+  }
+
+  @Override
+  public void threadSafeInvoke(Engine engine) throws IOException {
+    Table.forPath(engine, tablePath.toString()).checkpoint(engine, checkpointVersion);
+  }
+
+  @Override
+  public PostCommitHookType getType() {
+    return PostCommitHookType.CHECKPOINT;
+  }
+}

kernel/kernel-defaults/src/test/scala/io/delta/kernel/defaults/DeltaTableWriteSuiteBase.scala

@@ -26,8 +26,15 @@ import io.delta.kernel.internal.util.FileNames
 import io.delta.kernel.internal.util.Utils.singletonCloseableIterator
 import io.delta.kernel.internal.{SnapshotImpl, TableConfig, TableImpl}
 import io.delta.kernel.utils.FileStatus
-import io.delta.kernel.{Meta, Operation, Table, Transaction, TransactionBuilder, TransactionCommitResult}
-import io.delta.kernel.data.{ColumnarBatch, ColumnVector, FilteredColumnarBatch, Row}
+import io.delta.kernel.{
+  Meta,
+  Operation,
+  Table,
+  Transaction,
+  TransactionBuilder,
+  TransactionCommitResult
+}
+import io.delta.kernel.data.{ColumnVector, ColumnarBatch, FilteredColumnarBatch, Row}
 import io.delta.kernel.defaults.internal.data.DefaultColumnarBatch
 import io.delta.kernel.expressions.Literal
 import io.delta.kernel.expressions.Literal.ofInt
@@ -39,6 +46,7 @@ import io.delta.kernel.types.StructType
 import io.delta.kernel.utils.CloseableIterable.{emptyIterable, inMemoryIterable}
 import io.delta.kernel.utils.CloseableIterator
 import io.delta.kernel.Operation.CREATE_TABLE
+import io.delta.kernel.hook.PostCommitHook.PostCommitHookType
 import org.apache.commons.io.FileUtils
 import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.fs.Path
@@ -139,10 +147,14 @@ trait DeltaTableWriteSuiteBase extends AnyFunSuite with TestUtils {
     tablePath: String,
     result: TransactionCommitResult,
     expSize: Long): Unit = {
-    if (result.isReadyForCheckpoint) {
-      Table.forPath(engine, tablePath).checkpoint(engine, result.getVersion)
-      verifyLastCheckpointMetadata(tablePath, checkpointAt = result.getVersion, expSize)
-    }
+    result.getPostCommitHooks.forEach(
+      hook => {
+        if (hook.getType == PostCommitHookType.CHECKPOINT) {
+          hook.threadSafeInvoke(engine)
+          verifyLastCheckpointMetadata(tablePath, checkpointAt = result.getVersion, expSize)
+        }
+      }
+    )
   }
 
   /**
@@ -399,7 +411,7 @@ trait DeltaTableWriteSuiteBase extends AnyFunSuite with TestUtils {
     expVersion: Long,
     expIsReadyForCheckpoint: Boolean): Unit = {
     assert(result.getVersion === expVersion)
-    assert(result.isReadyForCheckpoint === expIsReadyForCheckpoint)
+    assertCheckpointReadiness(result, expIsReadyForCheckpoint)
   }
 
   def verifyTableProperties(
@@ -421,4 +433,16 @@ trait DeltaTableWriteSuiteBase extends AnyFunSuite with TestUtils {
     builder.append("]")
     checkAnswer(resultProperties, Seq(builder.toString()).map(TestRow(_)))
   }
+
+  def assertCheckpointReadiness(
+      txnResult: TransactionCommitResult,
+      isReadyForCheckpoint: Boolean): Unit = {
+    assert(
+      txnResult.getPostCommitHooks
+        .stream()
+        .anyMatch(
+          hook => hook.getType == PostCommitHookType.CHECKPOINT
+        ) === isReadyForCheckpoint
+    )
+  }
 }

kernel/kernel-defaults/src/test/scala/io/delta/kernel/defaults/DeltaTableWritesSuite.scala

@@ -25,6 +25,7 @@ import io.delta.kernel.engine.Engine
 import io.delta.kernel.exceptions._
 import io.delta.kernel.expressions.Literal
 import io.delta.kernel.expressions.Literal._
+import io.delta.kernel.hook.PostCommitHook.PostCommitHookType
 import io.delta.kernel.internal.checkpoints.CheckpointerSuite.selectSingleElement
 import io.delta.kernel.internal.util.SchemaUtils.casePreservingPartitionColNames
 import io.delta.kernel.internal.{SnapshotImpl, TableConfig}
@@ -131,7 +132,7 @@ class DeltaTableWritesSuite extends DeltaTableWriteSuiteBase with ParquetSuiteBa
       val txnResult = txn.commit(engine, emptyIterable())
 
       assert(txnResult.getVersion === 0)
-      assert(!txnResult.isReadyForCheckpoint)
+      assertCheckpointReadiness(txnResult, isReadyForCheckpoint = false)
 
       verifyCommitInfo(tablePath = tablePath, version = 0)
       verifyWrittenContent(tablePath, testSchema, Seq.empty)
@@ -350,7 +351,7 @@ class DeltaTableWritesSuite extends DeltaTableWriteSuiteBase with ParquetSuiteBa
       val txnResult = txn.commit(engine, emptyIterable())
 
       assert(txnResult.getVersion === 0)
-      assert(!txnResult.isReadyForCheckpoint)
+      assertCheckpointReadiness(txnResult, isReadyForCheckpoint = false)
 
       verifyCommitInfo(tablePath, version = 0, Seq("Part1", "part2"))
       verifyWrittenContent(tablePath, schema, Seq.empty)
@@ -368,7 +369,7 @@ class DeltaTableWritesSuite extends DeltaTableWriteSuiteBase with ParquetSuiteBa
       val txnResult = txn.commit(engine, emptyIterable())
 
       assert(txnResult.getVersion === 0)
-      assert(!txnResult.isReadyForCheckpoint)
+      assertCheckpointReadiness(txnResult, isReadyForCheckpoint = false)
 
       verifyCommitInfo(tablePath, version = 0)
       verifyWrittenContent(tablePath, schema, Seq.empty)