use data_encoding::BASE64;
use std::collections::HashSet;
use std::collections::VecDeque;
use std::path::PathBuf;
use tokio::sync::mpsc::channel;
use tokio::sync::mpsc::Sender;
use prost::Message;
use tokio::task;
use tokio_stream::wrappers::ReceiverStream;
use crate::proto::directory_service_server::DirectoryService;
use crate::proto::get_directory_request::ByWhat;
use crate::proto::Directory;
use crate::proto::GetDirectoryRequest;
use crate::proto::PutDirectoryResponse;
use tonic::{Request, Response, Result, Status, Streaming};
use tracing::{debug, instrument, warn};
pub struct SledDirectoryService {
db: sled::Db,
}
impl SledDirectoryService {
pub fn new(p: PathBuf) -> Result<Self, anyhow::Error> {
let config = sled::Config::default().use_compression(true).path(p);
let db = config.open()?;
Ok(Self { db })
}
}
/// Lookup a directory, optionally recurse, and send the result to the passed sender.
/// We pass in a txn, that has been opened on the outside.
/// It's up to the user to wrap this in a TransactionError appropriately.
/// This will open a sled txn to ensure a consistent view.
fn send_directories(
txn: &sled::transaction::TransactionalTree,
tx: &Sender<Result<Directory>>,
req: GetDirectoryRequest,
) -> Result<(), Status> {
// keep the list of directories to traverse
let mut deq: VecDeque<Vec<u8>> = VecDeque::new();
// look at the digest in the request and put it in the top of the queue.
match &req.by_what {
None => return Err(Status::invalid_argument("by_what needs to be specified")),
Some(ByWhat::Digest(digest)) => {
if digest.len() != 32 {
return Err(Status::invalid_argument("invalid digest length"));
}
deq.push_back(digest.clone());
}
}
// keep a list of all the Directory messages already sent, so we can omit sending the same.
let mut sent_directory_dgsts: HashSet<Vec<u8>> = HashSet::new();
// look up the directory at the top of the queue
while let Some(ref digest) = deq.pop_front() {
let digest_b64: String = BASE64.encode(digest);
match txn.get(digest) {
// The directory was not found, abort
Ok(None) => {
return Err(Status::not_found(format!(
"directory {} not found",
digest_b64
)))
}
// The directory was found, try to parse the data as Directory message
Ok(Some(data)) => match Directory::decode(&*data) {
Err(e) => {
warn!("unable to parse directory {}: {}", digest_b64, e);
return Err(Status::internal(format!(
"unable to parse directory {}",
digest_b64
)));
}
Ok(directory) => {
// Validate the retrieved Directory indeed has the
// digest we expect it to have, to detect corruptions.
let actual_digest = directory.digest();
if actual_digest != digest.clone() {
return Err(Status::data_loss(format!(
"requested directory with digest {}, but got {}",
digest_b64,
BASE64.encode(&actual_digest)
)));
}
// if recursion was requested, all its children need to be added to the queue.
// If a Directory message with the same digest has already
// been sent previously, we can skip enqueueing it.
// Same applies to when it already is in the queue.
if req.recursive {
for child_directory_node in &directory.directories {
if !sent_directory_dgsts.contains(&child_directory_node.digest)
&& !deq.contains(&child_directory_node.digest)
{
deq.push_back(child_directory_node.digest.clone());
}
}
}
// send the directory message to the client
if let Err(e) = tx.blocking_send(Ok(directory)) {
debug!("error sending: {}", e);
return Err(Status::internal("error sending"));
}
sent_directory_dgsts.insert(digest.to_vec());
}
},
// some storage error?
Err(e) => {
// TODO: check what this error really means
warn!("storage error: {}", e);
return Err(Status::internal("storage error"));
}
};
}
// nothing left, we're done
Ok(())
}
/// Consume directories, and insert them into the database.
/// Reject directory messages that refer to Directories not sent in the same stream.
fn insert_directories(
txn: &sled::transaction::TransactionalTree,
directories: &Vec<Directory>,
) -> Result<Vec<u8>, Status> {
// This keeps track of the seen directory keys.
// We don't need to keep the contents around, they're stored in the DB.
let mut seen_directory_dgsts: HashSet<Vec<u8>> = HashSet::new();
let mut last_directory_dgst: Option<Vec<u8>> = None;
for directory in directories {
// for each child directory this directory refers to, we need
// to ensure it has been seen already in this stream.
for child_directory in &directory.directories {
if !seen_directory_dgsts.contains(&child_directory.digest) {
return Err(Status::invalid_argument(format!(
"referred child directory {} not seen yet",
BASE64.encode(&child_directory.digest)
)));
}
}
// TODO: do we want to verify this somehow is connected to the current graph?
// theoretically, this currently allows uploading multiple
// disconnected graphs at the same time…
let dgst = directory.digest();
seen_directory_dgsts.insert(dgst.clone());
last_directory_dgst = Some(dgst.clone());
// check if the directory already exists in the database. We can skip
// inserting if it's already there, as that'd be a no-op.
match txn.get(dgst.clone()) {
Ok(None) => {
// insert the directory into the database
if let Err(e) = txn.insert(dgst, directory.encode_to_vec()) {
match e {
// TODO: conflict is a problem, as the whole transaction closure is retried?
sled::transaction::UnabortableTransactionError::Conflict => todo!(),
sled::transaction::UnabortableTransactionError::Storage(e) => {
warn!("storage error: {}", e);
return Err(Status::internal("storage error"));
}
}
}
}
Ok(Some(_)) => continue,
Err(e) => {
warn!("storage error: {}", e);
return Err(Status::internal("storage error"));
}
}
}
// no more directories to be send. Return the digest of the
// last (root) node, or an error if we don't receive a single one.
match last_directory_dgst {
Some(last_directory_dgst) => Ok(last_directory_dgst),
None => Err(Status::invalid_argument("no directories received")),
}
}
#[tonic::async_trait]
impl DirectoryService for SledDirectoryService {
type GetStream = ReceiverStream<Result<Directory>>;
#[instrument(skip(self))]
async fn get(
&self,
request: Request<GetDirectoryRequest>,
) -> Result<Response<Self::GetStream>, Status> {
let (tx, rx) = channel(5);
let req_inner = request.into_inner();
// clone self.db (cheap), so we don't refer to self in the thread.
let db = self.db.clone();
// kick off a thread
task::spawn_blocking(move || {
// open a DB transaction.
let txn_res = db.transaction(|txn| {
send_directories(txn, &tx, req_inner.clone())
.map_err(sled::transaction::ConflictableTransactionError::Abort)
});
// handle transaction errors
match txn_res {
Ok(()) => Ok(()),
Err(sled::transaction::TransactionError::Abort(status)) => {
// if the transaction was aborted, there was an error. Send it to the client
tx.blocking_send(Err(status))
}
Err(sled::transaction::TransactionError::Storage(e)) => {
warn!("storage error: {}", e);
tx.blocking_send(Err(Status::internal("storage error")))
}
}
});
// NOTE: this always returns an Ok response, with the first item in the
// stream being a potential error, instead of directly returning the
// first error.
// Peeking on the first element seems to be extraordinarily hard,
// and client code considers these two equivalent anyways.
let receiver_stream = ReceiverStream::new(rx);
Ok(Response::new(receiver_stream))
}
#[instrument(skip(self, request))]
async fn put(
&self,
request: Request<Streaming<Directory>>,
) -> Result<Response<PutDirectoryResponse>> {
let mut req_inner = request.into_inner();
// TODO: for now, we collect all Directory messages into a Vec, and
// pass it to the helper function.
// Ideally, we would validate things as we receive it, and have a way
// to reject early - but the semantics of transactions (and its
// retries) don't allow us to discard things that early anyways.
let mut directories: Vec<Directory> = Vec::new();
while let Some(directory) = req_inner.message().await? {
directories.push(directory)
}
let txn_res = self.db.transaction(|txn| {
insert_directories(txn, &directories)
.map_err(sled::transaction::ConflictableTransactionError::Abort)
});
match txn_res {
Ok(last_directory_dgst) => Ok(Response::new(PutDirectoryResponse {
root_digest: last_directory_dgst,
})),
Err(sled::transaction::TransactionError::Storage(e)) => {
warn!("storage error: {}", e);
Err(Status::internal("storage error"))
}
Err(sled::transaction::TransactionError::Abort(e)) => Err(e),
}
}
}
