From d46b56d0c37078efa7e8e166903b6c0dc13c4f33 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=99=BD=E9=B5=BA?= <ocean.wy@alibaba-inc.com>
Date: Mon, 14 Sep 2026 15:36:08 +0800
Subject: [PATCH] [flink] Preserve the configured scan rate with fractional
 subtask quotas

---
 .../orphan/job/ScanAndCleanFunction.java      | 16 ++------
 .../orphan/job/ScanAndCleanFunctionTest.java  | 40 +++++++++++++++++++
 2 files changed, 44 insertions(+), 12 deletions(-)
 create mode 100644 fluss-flink/fluss-flink-common/src/test/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunctionTest.java

diff --git a/fluss-flink/fluss-flink-common/src/main/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunction.java b/fluss-flink/fluss-flink-common/src/main/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunction.java
index 2b541746434..5e40aad6322 100644
--- a/fluss-flink/fluss-flink-common/src/main/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunction.java
+++ b/fluss-flink/fluss-flink-common/src/main/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunction.java
@@ -86,14 +86,9 @@ public void open(org.apache.flink.api.common.functions.OpenContext openContext)
         }
         audit = new AuditLogger();
         int parallelism = getRuntimeContext().getTaskInfo().getNumberOfParallelSubtasks();
-        int subtaskIndex = getRuntimeContext().getTaskInfo().getIndexOfThisSubtask();
-        // Distribute the configured rate as base + 1 extra for the first `remainder` subtasks.
-        // Flink does not provide a cross-JVM limiter here, so this is a best-effort job-level
-        // target. Each subtask gets at least 1/s; if parallelism exceeds the configured rate, the
-        // effective aggregate can exceed the target by that floor.
+        // Each worker owns its limiter; fractional rates preserve the best-effort job-level target.
         remoteFsOpRateLimiter =
-                RateLimiter.create(
-                        perSubtaskRate(remoteFsOpRateLimitPerSecond, parallelism, subtaskIndex));
+                RateLimiter.create(perSubtaskRate(remoteFsOpRateLimitPerSecond, parallelism));
     }
 
     @Override
@@ -241,11 +236,8 @@ private SafeDeleter createSafeDeleter(FileSystem fs, boolean dryRun) {
         return new SafeDeleter(fs, dryRun, audit, remoteFsOpRateLimiter);
     }
 
-    private static double perSubtaskRate(long totalRate, int parallelism, int subtaskIndex) {
-        long base = totalRate / parallelism;
-        long remainder = totalRate % parallelism;
-        long quota = base + (subtaskIndex < remainder ? 1L : 0L);
-        return Math.max(1.0, (double) quota);
+    static double perSubtaskRate(long totalRate, int parallelism) {
+        return ((double) totalRate) / parallelism;
     }
 
     private static final class DirVisit {
diff --git a/fluss-flink/fluss-flink-common/src/test/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunctionTest.java b/fluss-flink/fluss-flink-common/src/test/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunctionTest.java
new file mode 100644
index 00000000000..e697407e889
--- /dev/null
+++ b/fluss-flink/fluss-flink-common/src/test/java/org/apache/fluss/flink/action/orphan/job/ScanAndCleanFunctionTest.java
@@ -0,0 +1,40 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.fluss.flink.action.orphan.job;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/** Tests for scan filesystem rate allocation. */
+class ScanAndCleanFunctionTest {
+    @Test
+    void splitsNonDivisibleRateAcrossSubtasks() {
+        assertThat(ScanAndCleanFunction.perSubtaskRate(100, 16)).isEqualTo(6.25);
+    }
+
+    @Test
+    void doesNotRaiseRateWhenParallelismExceedsLimit() {
+        assertThat(ScanAndCleanFunction.perSubtaskRate(3, 8)).isEqualTo(0.375);
+    }
+
+    @Test
+    void preservesRateWithOneSubtask() {
+        assertThat(ScanAndCleanFunction.perSubtaskRate(100, 1)).isEqualTo(100);
+    }
+}