From a9c77cef49fc88205584e063b736d655ab7cb2e2 Mon Sep 17 00:00:00 2001
From: limu <limu@dewu.com>
Date: Sat, 13 Jun 2026 17:39:29 +0800
Subject: [PATCH] [core] Rewrite OSSFileIO.tryToWriteAtomic using atomic
 putObject API of the OSS SDK (#8226)

Paimon's existing OSSFileIO inherits from HadoopCompliantFileIO, with
file operations implemented underneath via Hadoop's AliyunOSSFileSystem.
In object storage scenarios, the default implementation of tryToWriteAtomic
follows the pattern of 'writing a temporary file followed by renaming'.
However, renaming on OSS is essentially a copy-then-delete process and
not an atomic operation.

Rewrite the implementation of tryToWriteAtomic, and directly call the
conditional write API (put-if-absent) of the OSS SDK, so as to implement
the atomic 'write if not exists' semantics without relying on external locks.
---
 .../org/apache/paimon/fs/PluginFileIO.java    |  5 +++
 .../java/org/apache/paimon/oss/OSSFileIO.java | 32 +++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/paimon-common/src/main/java/org/apache/paimon/fs/PluginFileIO.java b/paimon-common/src/main/java/org/apache/paimon/fs/PluginFileIO.java
index 2af4919f0815..d5b62a2944cf 100644
--- a/paimon-common/src/main/java/org/apache/paimon/fs/PluginFileIO.java
+++ b/paimon-common/src/main/java/org/apache/paimon/fs/PluginFileIO.java
@@ -91,6 +91,11 @@ public boolean rename(Path src, Path dst) throws IOException {
         return wrap(() -> fileIO(src).rename(src, dst));
     }
 
+    @Override
+    public boolean tryToWriteAtomic(Path path, String content) throws IOException {
+        return wrap(() -> fileIO(path).tryToWriteAtomic(path, content));
+    }
+
     private FileIO fileIO(Path path) throws IOException {
         if (lazyFileIO == null) {
             synchronized (this) {
diff --git a/paimon-filesystems/paimon-oss-impl/src/main/java/org/apache/paimon/oss/OSSFileIO.java b/paimon-filesystems/paimon-oss-impl/src/main/java/org/apache/paimon/oss/OSSFileIO.java
index 85d7e8cf9ec8..c5e54dac48a6 100644
--- a/paimon-filesystems/paimon-oss-impl/src/main/java/org/apache/paimon/oss/OSSFileIO.java
+++ b/paimon-filesystems/paimon-oss-impl/src/main/java/org/apache/paimon/oss/OSSFileIO.java
@@ -28,7 +28,9 @@
 import org.apache.paimon.utils.ReflectionUtils;
 
 import com.aliyun.oss.OSSClient;
+import com.aliyun.oss.OSSException;
 import com.aliyun.oss.common.comm.ServiceClient;
+import com.aliyun.oss.model.ObjectMetadata;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.aliyun.oss.AliyunOSSFileSystem;
@@ -36,9 +38,11 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -180,6 +184,34 @@ protected AliyunOSSFileSystem createFileSystem(org.apache.hadoop.fs.Path path) {
         }
     }
 
+    @Override
+    public boolean tryToWriteAtomic(Path path, String content) throws IOException {
+        URI uri = path.toUri();
+        String bucket = uri.getHost();
+        String objectKey = uri.getPath().substring(1);
+        byte[] bytes = content.getBytes(StandardCharsets.UTF_8);
+
+        ObjectMetadata metadata = new ObjectMetadata();
+        metadata.setContentLength(bytes.length);
+        metadata.setHeader("x-oss-forbid-overwrite", "true");
+
+        AliyunOSSFileSystem fs = (AliyunOSSFileSystem) getFileSystem(path(path));
+        AliyunOSSFileSystemStore store = fs.getStore();
+        try {
+            OSSClient ossClient = ReflectionUtils.getPrivateFieldValue(store, "ossClient");
+            ossClient.putObject(bucket, objectKey, new ByteArrayInputStream(bytes), metadata);
+            return true;
+        } catch (OSSException e) {
+            if ("FileAlreadyExists".equals(e.getErrorCode())) {
+                LOG.warn("Failed to atomic write {}: object already exists", path);
+                return false;
+            }
+            throw new IOException("Failed to atomic write " + path, e);
+        } catch (Exception e) {
+            throw new IOException("Failed to atomic write " + path, e);
+        }
+    }
+
     @Override
     public void close() {
         if (!allowCache) {