From 1ae7c03e864cecc2f0059555a07d5d2cb0c5f24e Mon Sep 17 00:00:00 2001
From: chaokunyang <shawn.ck.yang@gmail.com>
Date: Thu, 20 Feb 2020 20:38:51 +0800
Subject: [PATCH] fix concurrently extract file (#7225)

---
 .../org/ray/runtime/util/BinaryFileUtil.java  | 49 +++++++++++++------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/java/runtime/src/main/java/org/ray/runtime/util/BinaryFileUtil.java b/java/runtime/src/main/java/org/ray/runtime/util/BinaryFileUtil.java
index 4c5cc402f..df8cb8a6f 100644
--- a/java/runtime/src/main/java/org/ray/runtime/util/BinaryFileUtil.java
+++ b/java/runtime/src/main/java/org/ray/runtime/util/BinaryFileUtil.java
@@ -4,6 +4,8 @@ import com.google.common.base.Preconditions;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.RandomAccessFile;
+import java.nio.channels.FileLock;
 import java.nio.file.Files;
 import java.nio.file.Paths;
 import org.apache.commons.io.FileUtils;
@@ -22,27 +24,42 @@ public class BinaryFileUtil {
   public static final String CORE_WORKER_JAVA_LIBRARY =
       System.mapLibraryName("core_worker_library_java");
 
+  /**
+   * Extract a resource file to <code>destDir</code>.
+   * Note that this a process-safe operation. If multi processes extract the file to same
+   * directory concurrently, this operation will be protected by a file lock.
+   *
+   * @param destDir  a directory to extract resource file to
+   * @param fileName resource file name
+   * @return extracted resource file
+   */
   public static File getFile(String destDir, String fileName) {
-    File file = new File(String.format("%s/%s", destDir, fileName));
-    if (file.exists()) {
-      return file;
-    }
-
-    final File dir = file.getParentFile();
-    try {
-      if (!dir.exists()) {
+    final File dir = new File(destDir);
+    if (!dir.exists()) {
+      try {
         FileUtils.forceMkdir(dir);
+      } catch (IOException e) {
+        throw new RuntimeException("Couldn't make directory: " + dir.getAbsolutePath(), e);
       }
-    } catch (IOException e) {
-      throw new RuntimeException("Couldn't make directory: " + dir.getAbsolutePath(), e);
     }
-    // File does not exist.
-    try (InputStream is = BinaryFileUtil.class.getResourceAsStream("/" + fileName)) {
-      Preconditions.checkNotNull(is, "{} doesn't exist.", fileName);
-      Files.copy(is, Paths.get(file.getCanonicalPath()));
+    String lockFilePath = destDir + File.separator + "file_lock";
+    try (FileLock ignored = new RandomAccessFile(lockFilePath, "rw")
+        .getChannel().lock()) {
+      File file = new File(String.format("%s/%s", destDir, fileName));
+      if (file.exists()) {
+        return file;
+      }
+
+      // File does not exist.
+      try (InputStream is = BinaryFileUtil.class.getResourceAsStream("/" + fileName)) {
+        Preconditions.checkNotNull(is, "{} doesn't exist.", fileName);
+        Files.copy(is, Paths.get(file.getCanonicalPath()));
+      } catch (IOException e) {
+        throw new RuntimeException("Couldn't get temp file from resource " + fileName, e);
+      }
+      return file;
     } catch (IOException e) {
-      throw new RuntimeException("Couldn't get temp file from resource " + fileName, e);
+      throw new RuntimeException(e);
     }
-    return file;
   }
 }