[FIX] S3: Fallback bucket should not apply bucket prefix

docs/modules/servers/partials/configure/blobstore.adoc

@@ -166,6 +166,8 @@ Unless a special case like storing blobs of deleted messages.
 | objectstorage.namespace.read.fallback
 | BlobStore fallback bucket name. Allows to fallback to a previous used bucket when blob is missing from the default one.
 It can be useful when migrating blobs to a new bucket for example.
+This is a read only fallback: James never writes to, nor deletes from, that bucket.
+This bucket name is used as is: `objectstorage.bucketPrefix` is not applied to it.
 |===
 
 ==== SSE-C Configuration

server/apps/distributed-app/helm-chart/james/configs/blob.properties

@@ -42,7 +42,9 @@ cache.sizeThresholdInBytes=16 KiB
 objectstorage.namespace=james-${env:JAMES_BUCKET_SUFFIX}
 
 # Fallback bucket name
-# Optional, read this bucket when default bukcket reads fails if configured
+# Optional, read this bucket when reads on the default bucket fail, if configured.
+# This is a read only fallback: blobs are never written to nor deleted from this bucket.
+# Note: this name is used as is, `objectstorage.bucketPrefix` is not applied to it.
 # objectstorage.namespace.read.fallback=james-fallback
 
 # ========================================= ObjectStorage on S3 =============================================

server/apps/distributed-app/sample-configuration/blob.properties

@@ -88,7 +88,9 @@ cache.enable=false
 # objectstorage.namespace=james
 
 # Fallback bucket name
-# Optional, read this bucket when default bukcket reads fails if configured
+# Optional, read this bucket when reads on the default bucket fail, if configured.
+# This is a read only fallback: blobs are never written to nor deleted from this bucket.
+# Note: this name is used as is, `objectstorage.bucketPrefix` is not applied to it.
 # objectstorage.namespace.read.fallback=james-fallback
 
 # ========================================= ObjectStorage on S3 =============================================

server/apps/distributed-pop3-app/sample-configuration/blob.properties

@@ -58,7 +58,9 @@ cache.enable=false
 # objectstorage.namespace=james
 
 # Fallback bucket name
-# Optional, read this bucket when default bukcket reads fails if configured
+# Optional, read this bucket when reads on the default bucket fail, if configured.
+# This is a read only fallback: blobs are never written to nor deleted from this bucket.
+# Note: this name is used as is, `objectstorage.bucketPrefix` is not applied to it.
 # objectstorage.namespace.read.fallback=james-fallback
 
 # ========================================= ObjectStorage on S3 =============================================

server/apps/postgres-app/sample-configuration-distributed/blob.properties

@@ -50,7 +50,9 @@ encryption.aes.enable=false
 # objectstorage.namespace=james
 
 # Fallback bucket name
-# Optional, read this bucket when default bukcket reads fails if configured
+# Optional, read this bucket when reads on the default bucket fail, if configured.
+# This is a read only fallback: blobs are never written to nor deleted from this bucket.
+# Note: this name is used as is, `objectstorage.bucketPrefix` is not applied to it.
 # objectstorage.namespace.read.fallback=james-fallback
 
 # ========================================= ObjectStorage on S3 =============================================

server/apps/scaling-pulsar-smtp/sample-configuration/blob.properties

@@ -68,7 +68,9 @@ cache.enable=false
 # objectstorage.namespace=james
 
 # Fallback bucket name
-# Optional, read this bucket when default bukcket reads fails if configured
+# Optional, read this bucket when reads on the default bucket fail, if configured.
+# This is a read only fallback: blobs are never written to nor deleted from this bucket.
+# Note: this name is used as is, `objectstorage.bucketPrefix` is not applied to it.
 # objectstorage.namespace.read.fallback=james-fallback
 
 # ========================================= ObjectStorage on S3 =============================================

server/blob/blob-s3/src/main/java/org/apache/james/blob/objectstorage/aws/S3BlobStoreDAO.java

@@ -173,8 +173,7 @@ private Mono<FluxResponse> getObject(BucketName bucketName, BlobId blobId) {
         return getObjectFromStore(bucketName, blobId)
             .onErrorResume(e -> e instanceof NoSuchKeyException || e instanceof NoSuchBucketException, e -> {
                 if (fallbackNamespace.isPresent() && bucketNameResolver.isNameSpace(bucketName)) {
-                    BucketName resolvedFallbackBucketName = bucketNameResolver.resolve(fallbackNamespace.get());
-                    return getObjectFromStore(resolvedFallbackBucketName, blobId);
+                    return getObjectFromStore(fallbackNamespace.get(), blobId);
                 }
                 return Mono.error(e);
             });
@@ -229,8 +228,7 @@ private Mono<ResponseBytes<GetObjectResponse>> getObjectBytes(BucketName bucketN
         return getObjectBytesFromStore(bucketName, blobId)
                 .onErrorResume(e -> e instanceof NoSuchKeyException || e instanceof NoSuchBucketException, e -> {
                     if (fallbackNamespace.isPresent() && bucketNameResolver.isNameSpace(bucketName)) {
-                        BucketName resolvedFallbackBucketName = bucketNameResolver.resolve(fallbackNamespace.get());
-                        return getObjectBytesFromStore(resolvedFallbackBucketName, blobId);
+                        return getObjectBytesFromStore(fallbackNamespace.get(), blobId);
                     }
                     return Mono.error(e);
                 });

server/blob/blob-s3/src/test/java/org/apache/james/blob/objectstorage/aws/S3BlobStoreDAOTest.java

@@ -162,6 +162,30 @@ void readBytesShouldFallbackToDefinedBucketWhenFailingOnDefaultOne() {
         assertThat(bytes).isEqualTo(ELEVEN_KILOBYTES);
     }
 
+    @Test
+    void fallbackBucketNameShouldNotBeAffectedByBucketPrefix(DockerAwsS3Container dockerAwsS3) {
+        S3BlobStoreConfiguration prefixedConfiguration = S3BlobStoreConfiguration.builder()
+            .authConfiguration(AwsS3AuthConfiguration.builder()
+                .endpoint(dockerAwsS3.getEndpoint())
+                .accessKeyId(DockerAwsS3Container.ACCESS_KEY_ID)
+                .secretKey(DockerAwsS3Container.SECRET_ACCESS_KEY)
+                .build())
+            .region(dockerAwsS3.dockerAwsS3().region())
+            .defaultBucketName(BucketName.DEFAULT)
+            .bucketPrefix("prefix-")
+            .fallbackBucketName(Optional.of(fallbackBucket))
+            .build();
+        S3BlobStoreDAO prefixedStore = new S3BlobStoreDAO(s3ClientFactory, prefixedConfiguration, new TestBlobId.Factory(), S3RequestOption.DEFAULT);
+
+        TestBlobId blobId = new TestBlobId("id");
+        // Save in the un-prefixed fallback bucket
+        Mono.from(testee.save(fallbackBucket, blobId, ELEVEN_KILOBYTES)).block();
+
+        InputStream read = prefixedStore.read(BucketName.DEFAULT, blobId).payload();
+
+        assertThat(read).hasSameContentAs(ELEVEN_KILOBYTES.asInputStream().payload());
+    }
+
     @Test
     void shouldNotReadOnFallbackBucketWhenNotReadingOnDefaultOne() {
         BlobStoreDAO store = testee();