From c7bfbffd31afcd78b783df3d1068d0707d140e3c Mon Sep 17 00:00:00 2001
From: Vishesh Garg <gargvishesh@gmail.com>
Date: Mon, 11 Mar 2024 18:30:34 +0530
Subject: [PATCH] Correct the API used to fetch the version for a GCS object
 (#16097)

Current API used to fetch the version for a GCS object is incorrect. This PR fixes that API.

(cherry picked from commit 2dd8b16467e97fb51fd6d3985424f9521ef6cb36)
---
 .../apache/druid/storage/google/GoogleStorage.java  | 13 +++++++++++--
 .../google/GoogleTimestampVersionedDataFinder.java  |  2 +-
 .../druid/storage/google/GoogleStorageTest.java     |  6 +++---
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleStorage.java b/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleStorage.java
index 57c2ac1843bf..6a5d17f7c242 100644
--- a/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleStorage.java
+++ b/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleStorage.java
@@ -198,13 +198,22 @@ public long size(final String bucket, final String path) throws IOException
     return blob.getSize();
   }
 
+  /**
+   * Return the etag for an object. This is a value that changes whenever the object's data or metadata changes and is
+   * typically but not always the MD5 hash of the object. Ref:
+   * <a href="https://cloud.google.com/storage/docs/hashes-etags#etags">ETags</a>
+   * @param bucket
+   * @param path
+   * @return
+   * @throws IOException
+   */
   public String version(final String bucket, final String path) throws IOException
   {
-    Blob blob = storage.get().get(bucket, path, Storage.BlobGetOption.fields(Storage.BlobField.GENERATION));
+    Blob blob = storage.get().get(bucket, path, Storage.BlobGetOption.fields(Storage.BlobField.ETAG));
     if (blob == null) {
       throw new IOE("Failed to fetch google cloud storage object from bucket [%s] and path [%s].", bucket, path);
     }
-    return blob.getGeneratedId();
+    return blob.getEtag();
   }
 
   /***
diff --git a/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleTimestampVersionedDataFinder.java b/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleTimestampVersionedDataFinder.java
index 01ae094912cf..d95577d5be6e 100644
--- a/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleTimestampVersionedDataFinder.java
+++ b/extensions-core/google-extensions/src/main/java/org/apache/druid/storage/google/GoogleTimestampVersionedDataFinder.java
@@ -76,7 +76,7 @@ public URI getLatestVersion(URI descriptorBase, @Nullable Pattern pattern)
       return latest;
     }
     catch (IOException e) {
-      throw new RuntimeException();
+      throw new RuntimeException(e);
     }
   }
 }
diff --git a/extensions-core/google-extensions/src/test/java/org/apache/druid/storage/google/GoogleStorageTest.java b/extensions-core/google-extensions/src/test/java/org/apache/druid/storage/google/GoogleStorageTest.java
index 0a6d346d1c40..15fbde3c5211 100644
--- a/extensions-core/google-extensions/src/test/java/org/apache/druid/storage/google/GoogleStorageTest.java
+++ b/extensions-core/google-extensions/src/test/java/org/apache/druid/storage/google/GoogleStorageTest.java
@@ -203,18 +203,18 @@ public void testSize() throws IOException
   @Test
   public void testVersion() throws IOException
   {
-    final String version = "7";
+    final String etag = "abcd";
     EasyMock.expect(mockStorage.get(
         EasyMock.eq(BUCKET),
         EasyMock.eq(PATH),
         EasyMock.anyObject(Storage.BlobGetOption.class)
     )).andReturn(blob);
 
-    EasyMock.expect(blob.getGeneratedId()).andReturn(version);
+    EasyMock.expect(blob.getEtag()).andReturn(etag);
 
     EasyMock.replay(mockStorage, blob);
 
-    assertEquals(version, googleStorage.version(BUCKET, PATH));
+    assertEquals(etag, googleStorage.version(BUCKET, PATH));
   }
 
   @Test