WIP: try to fix #93, and improve S3 ListObjects (v1 and v2) API calls

src/api/s3_list.rs

@@ -68,26 +68,63 @@ pub async fn handle_list(
 	let mut result_keys = BTreeMap::<String, ListResultInfo>::new();
 	let mut result_common_prefixes = BTreeSet::<String>::new();
 
-	let mut next_chunk_start = if query.is_v2 {
+	// Determine the key from where we want to start fetch objects
+	// from the database, and whether the object at this key must
+	// be included or excluded from the response.
+	// This key can be the prefix in the base case, or intermediate
+	// points in the dataset if we are continuing a previous listing.
+	#[allow(clippy::collapsible_else_if)]
+	let (mut next_chunk_start, mut next_chunk_exclude_start) = if query.is_v2 {
 		if let Some(ct) = &query.continuation_token {
-			String::from_utf8(base64::decode(ct.as_bytes())?)?
+			// In V2 mode, the continuation token is defined as an opaque
+			// string in the spec, so we can do whatever we want with it.
+			// In our case, it is defined as either [ or ] (for include
+			// and exclude, respectively), followed by a base64 string
+			// representing the key to start with.
+			let exclude = match &ct[..1] {
+				"[" => false,
+				"]" => true,
+				_ => return Err(Error::BadRequest("Invalid continuation token".to_string())),
+			};
+			(
+				String::from_utf8(base64::decode(ct[1..].as_bytes())?)?,
+				exclude,
+			)
+		} else if let Some(sa) = &query.start_after {
+			// StartAfter has defined semantics in the spec:
+			// start listing at the first key immediately after.
+			(sa.clone(), true)
 		} else {
-			query
+			// In the case where neither is specified, we start
-				.start_after
+			// listing at the specified prefix. If an object has this
-				.clone()
+			// exact same key, we include it. (TODO is this correct?)
-				.unwrap_or_else(|| query.prefix.clone())
+			(query.prefix.clone(), false)
 		}
 	} else {
-		query.marker.clone().unwrap_or_else(|| query.prefix.clone())
+		if let Some(mk) = &query.marker {
+			// In V1 mode, the spec defines the Marker value to mean
+			// the same thing as the StartAfter value in V2 mode.
+			(mk.clone(), true)
+		} else {
+			// Base case, same as in V2 mode
+			(query.prefix.clone(), false)
+		}
 	};
 
 	debug!(
-		"List request: `{:?}` {} `{}`",
+		"List request: `{:?}` {} `{}`, start from {}, exclude first {}",
-		query.delimiter, query.max_keys, query.prefix
+		query.delimiter, query.max_keys, query.prefix, next_chunk_start, next_chunk_exclude_start
 	);
 
+	// `truncated` is a boolean that determines whether there are
+	// more items to be added.
 	let truncated;
+	// `last_processed_item` is the key of the last item
+	// that was included in the listing before truncating.
+	let mut last_processed_item = None;
+
 	'query_loop: loop {
+		// Fetch objects
 		let objects = garage
 			.object_table
 			.get_range(
@@ -103,38 +140,85 @@ pub async fn handle_list(
 			query.max_keys + 1,
 			objects.len()
 		);
+		let current_chunk_start = next_chunk_start.clone();
 
+		// Iterate on returned objects and add them to the response.
+		// If a delimiter is specified, we take care of grouping objects
+		// into CommonPrefixes.
 		for object in objects.iter() {
+			// If we have retrieved an object that doesn't start with
+			// the prefix, we know we have finished listing our stuff.
 			if !object.key.starts_with(&query.prefix) {
-				truncated = None;
+				truncated = false;
 				break 'query_loop;
 			}
 
-			if query.is_v2 && query.start_after.as_ref() == Some(&object.key) {
+			// Exclude the starting key if we have to.
+			if object.key == next_chunk_start && next_chunk_exclude_start {
 				continue;
 			}
 
-			if let Some(version) = object.versions().iter().find(|x| x.is_data()) {
+			// Find if this object has a currently valid (non-deleted,
-				if result_keys.len() + result_common_prefixes.len() >= query.max_keys {
+			// non-still-uploading) version. If not, skip it.
-					truncated = Some(object.key.to_string());
+			let version = match object.versions().iter().find(|x| x.is_data()) {
-					break 'query_loop;
+				Some(v) => v,
-				}
+				None => continue,
-				let common_prefix = if let Some(delimiter) = &query.delimiter {
+			};
-					let relative_key = &object.key[query.prefix.len()..];
+
-					relative_key
+			// If we don't have space to add this object to our response,
+			// we will need to stop here and mark the key of this object
+			// as the marker from where
+			// we want to start again in the next list call.
+			let cannot_add = result_keys.len() + result_common_prefixes.len() >= query.max_keys;
+
+			// Determine whether this object should be grouped inside
+			// a CommonPrefix because it contains the delimiter,
+			// or if it should be returned as an object.
+			let common_prefix = match &query.delimiter {
+				Some(delimiter) => object.key[query.prefix.len()..]
 					.find(delimiter)
-						.map(|i| &object.key[..query.prefix.len() + i + delimiter.len()])
+					.map(|i| &object.key[..query.prefix.len() + i + delimiter.len()]),
-				} else {
+				None => None,
-					None
 			};
 			if let Some(pfx) = common_prefix {
+				// In the case where this object must be grouped in a
+				// common prefix, handle it here.
+				if !result_common_prefixes.contains(pfx) {
+					// Determine the first listing key that starts after
+					// the common prefix, by finding the next possible
+					// string by alphabetical order.
+					let mut first_key_after_prefix = pfx.to_string();
+					let tail = first_key_after_prefix.pop().unwrap();
+					first_key_after_prefix.push(((tail as u8) + 1) as char);
+
+					// If this were the end of the chunk,
+					// the next chunk should start after this prefix
+					next_chunk_start = first_key_after_prefix;
+					next_chunk_exclude_start = false;
+
+					if cannot_add {
+						truncated = true;
+						break 'query_loop;
+					}
 					result_common_prefixes.insert(pfx.to_string());
-				} else {
+				}
+				last_processed_item = Some(object.key.clone());
+				continue;
+			};
+
+			// This is not a common prefix, we want to add it to our
+			// response directly.
+			next_chunk_start = object.key.clone();
+
+			if cannot_add {
+				truncated = true;
+				next_chunk_exclude_start = false;
+				break 'query_loop;
+			}
+
 			let meta = match &version.state {
 				ObjectVersionState::Complete(ObjectVersionData::Inline(meta, _)) => meta,
-						ObjectVersionState::Complete(ObjectVersionData::FirstBlock(meta, _)) => {
+				ObjectVersionState::Complete(ObjectVersionData::FirstBlock(meta, _)) => meta,
-							meta
-						}
 				_ => unreachable!(),
 			};
 			let info = match result_keys.get(&object.key) {
@@ -145,22 +229,31 @@ pub async fn handle_list(
 				},
 				Some(_lri) => {
 					return Err(Error::InternalError(GarageError::Message(format!(
-								"Duplicate key?? {}",
+						"Duplicate key?? {} (this is a bug, please report it)",
 						object.key
 					))))
 				}
 			};
 			result_keys.insert(object.key.clone(), info);
-				};
+			last_processed_item = Some(object.key.clone());
-			}
+			next_chunk_exclude_start = true;
 		}
+
+		// If our database returned less objects than what we were asking for,
+		// it means that no more objects are in the bucket. So we stop here.
 		if objects.len() < query.max_keys + 1 {
-			truncated = None;
+			truncated = false;
 			break 'query_loop;
 		}
-		if !objects.is_empty() {
+
-			next_chunk_start = objects[objects.len() - 1].key.clone();
+		// Sanity check: we should have added at least an object
+		// or a prefix to our returned result.
+		if next_chunk_start == current_chunk_start || last_processed_item.is_none() {
+			return Err(Error::InternalError(GarageError::Message(format!(
+							"S3 ListObject: made no progress, still starting at {} (this is a bug, please report it)", next_chunk_start))));
 		}
+
+		// Loop and fetch more objects
 	}
 
 	let mut result = s3_xml::ListBucketResult {
@@ -181,11 +274,10 @@ pub async fn handle_list(
 			true => Some(s3_xml::Value("url".to_string())),
 			false => None,
 		},
-
 		key_count: Some(s3_xml::IntValue(
 			result_keys.len() as i64 + result_common_prefixes.len() as i64,
 		)),
-		is_truncated: s3_xml::Value(format!("{}", truncated.is_some())),
+		is_truncated: s3_xml::Value(format!("{}", truncated)),
 		contents: vec![],
 		common_prefixes: vec![],
 	};
@@ -197,16 +289,27 @@ pub async fn handle_list(
 		if let Some(sa) = &query.start_after {
 			result.start_after = Some(uriencode_maybe(sa, query.urlencode_resp));
 		}
-		if let Some(nct) = truncated {
+		if truncated {
-			result.next_continuation_token = Some(s3_xml::Value(base64::encode(nct.as_bytes())));
+			let b64 = base64::encode(next_chunk_start.as_bytes());
+			let nct = if next_chunk_exclude_start {
+				format!("]{}", b64)
+			} else {
+				format!("[{}", b64)
+			};
+			result.next_continuation_token = Some(s3_xml::Value(nct));
 		}
 	} else {
 		// TODO: are these supposed to be urlencoded when encoding-type is URL??
 		if let Some(mkr) = &query.marker {
 			result.marker = Some(uriencode_maybe(mkr, query.urlencode_resp));
 		}
-		if let Some(next_marker) = truncated {
+		if truncated {
-			result.next_marker = Some(uriencode_maybe(&next_marker, query.urlencode_resp));
+			if let Some(lpi) = last_processed_item {
+				result.next_marker = Some(uriencode_maybe(&lpi, query.urlencode_resp));
+			} else {
+				return Err(Error::InternalError(GarageError::Message(
+								"S3 ListObject: last_processed_item is None but the response was truncated, indicating that many items were processed (this is a bug, please report it)".to_string())));
+			}
 		}
 	}
 
@@ -221,7 +324,6 @@ pub async fn handle_list(
 	}
 
 	for pfx in result_common_prefixes.iter() {
-		//TODO: in V1, are these urlencoded when urlencode_resp is true ?? (proably)
 		result.common_prefixes.push(s3_xml::CommonPrefix {
 			prefix: uriencode_maybe(pfx, query.urlencode_resp),
 		});