api: various fixes

src/api/s3/multipart.rs

@@ -114,14 +114,17 @@ pub async fn handle_put_part(
 		extra: request_checksum_value(req.headers())?,
 	};
 
-	// Read first chuck, and at the same time try to get object to see if it exists
 	let key = key.to_string();
 
 	let (req_head, mut req_body) = req.into_parts();
 
+	// Before we stream the body, configure the needed checksums.
 	req_body.add_expected_checksums(expected_checksums.clone());
 	// TODO: avoid parsing encryption headers twice...
 	if !EncryptionParams::new_from_headers(&garage, &req_head.headers)?.is_encrypted() {
+		// For non-encrypted objects, we need to compute the md5sum in all cases
+		// (even if content-md5 is not set), because it is used as an etag of the
+		// part, which is in turn used in the etag computation of the whole object
 		req_body.add_md5();
 	}
 
@@ -130,6 +133,7 @@ pub async fn handle_put_part(
 
 	let mut chunker = StreamChunker::new(stream, garage.config.block_size);
 
+	// Read first chuck, and at the same time try to get object to see if it exists
 	let ((_, object_version, mut mpu), first_block) =
 		futures::try_join!(get_upload(&ctx, &key, &upload_id), chunker.next(),)?;
 
@@ -186,7 +190,6 @@ pub async fn handle_put_part(
 	garage.version_table.insert(&version).await?;
 
 	// Copy data to version
-	// TODO don't duplicate checksums
 	let (total_size, _, _) = read_and_put_blocks(
 		&ctx,
 		&version,
@@ -198,7 +201,7 @@ pub async fn handle_put_part(
 	)
 	.await?;
 
-	// Verify that checksums map
+	// Verify that checksums match
 	let checksums = stream_checksums
 		.await
 		.ok_or_internal_error("checksum calculation")??;

src/api/s3/put.rs

@@ -79,9 +79,14 @@ pub async fn handle_put(
 	// Determine whether object should be encrypted, and if so the key
 	let encryption = EncryptionParams::new_from_headers(&ctx.garage, req.headers())?;
 
+	// The request body is a special ReqBody object (see garage_api_common::signature::body)
+	// which supports calculating checksums while streaming the data.
+	// Before we start streaming, we configure it to calculate all the checksums we need.
 	let mut req_body = req.into_body();
 	req_body.add_expected_checksums(expected_checksums.clone());
 	if !encryption.is_encrypted() {
+		// For non-encrypted objects, we need to compute the md5sum in all cases
+		// (even if content-md5 is not set), because it is used as the object etag
 		req_body.add_md5();
 	}