Remove Exists Check from S3 Repository Deletes (elastic#40931)

* The check doesn't add much if anything practically, since the S3 repository is eventually consistent and we only log the non-existence of a blob anyway
  * We don't do the check on writes for this very reason and documented it as such
  * Removing the check saves one API call per single delete speeding up the deletion process and lowering costs

plugins/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobContainer.java

@@ -119,9 +119,6 @@ public void writeBlobAtomic(String blobName, InputStream inputStream, long blobS
 
     @Override
     public void deleteBlob(String blobName) throws IOException {
-        if (blobExists(blobName) == false) {
-            throw new NoSuchFileException("Blob [" + blobName + "] does not exist");
-        }
         deleteBlobIgnoringIfNotExists(blobName);
     }
 

plugins/repository-s3/src/test/java/org/elasticsearch/repositories/s3/S3BlobStoreContainerTests.java

@@ -65,6 +65,11 @@ protected BlobStore newBlobStore() {
         return randomMockS3BlobStore();
     }
 
+    @Override
+    public void testDeleteBlob() {
+        assumeFalse("not implemented because of S3's weak consistency model", true);
+    }
+
     @Override
     public void testVerifyOverwriteFails() {
         assumeFalse("not implemented because of S3's weak consistency model", true);

server/src/main/java/org/elasticsearch/common/blobstore/BlobContainer.java

@@ -100,7 +100,7 @@ public interface BlobContainer {
 
     /**
      * Deletes the blob with the given name, if the blob exists. If the blob does not exist,
-     * this method throws a NoSuchFileException.
+     * this method may throw a {@link NoSuchFileException} if the underlying implementation supports an existence check before delete.
      *
      * @param   blobName
      *          The name of the blob to delete.
@@ -120,9 +120,7 @@ default void deleteBlobsIgnoringIfNotExists(List<String> blobNames) throws IOExc
         IOException ioe = null;
         for (String blobName : blobNames) {
             try {
-                deleteBlob(blobName);
-            } catch (NoSuchFileException e) {
-                // ignored
+                deleteBlobIgnoringIfNotExists(blobName);
             } catch (IOException e) {
                 if (ioe == null) {
                     ioe = e;