Room State Management #44

Manually merged
projectmoon merged 11 commits from room-state-management into master 2020-11-10 20:58:50 +00:00
4 changed files with 253 additions and 49 deletions
Showing only changes of commit fb24090952 - Show all commits

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@ -25,12 +25,18 @@ impl Database {
fn new_db(db: sled::Db) -> Result<Database, DataError> {
let migrations = db.open_tree("migrations")?;
Ok(Database {
let database = Database {
db: db.clone(),
variables: Variables::new(&db)?,
migrations: Migrations(migrations),
rooms: Rooms::new(&db)?,
})
};
//Start any event handlers.
database.rooms.start_handler();
info!("Opened database.");
Ok(database)
}
pub fn new<P: AsRef<Path>>(path: P) -> Result<Database, DataError> {

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@ -26,6 +26,9 @@ pub enum DataError {
#[error("expected i32, but i32 schema was violated")]
I32SchemaViolation,
#[error("unexpected or corruptd data bytes")]
InvalidValue,
#[error("expected string, but utf8 schema was violated: {0}")]
Utf8chemaViolation(#[from] std::str::Utf8Error),

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@ -1,9 +1,16 @@
use crate::db::errors::DataError;
use crate::db::schema::convert_u64;
use byteorder::BigEndian;
use log::{error, log_enabled, trace};
use sled::transaction::TransactionalTree;
use sled::Transactional;
use sled::Tree;
use sled::{CompareAndSwapError, Tree};
use std::collections::HashSet;
use std::str;
use std::time::{SystemTime, UNIX_EPOCH};
use tokio::task::JoinHandle;
use zerocopy::byteorder::U64;
use zerocopy::AsBytes;
#[derive(Clone)]
pub struct Rooms {
@ -15,8 +22,23 @@ pub struct Rooms {
/// Username -> list of room IDs user is in.
pub(in crate::db) username_roomids: Tree,
/// Room ID(str) 0xff event ID(str) -> timestamp. Records event
/// IDs that we have received, so we do not process twice.
pub(in crate::db) roomeventid_timestamp: Tree,
/// Room ID(str) 0xff timestamp(u64) -> event ID. Records event
/// IDs with timestamp as the primary key instead. Exists to allow
/// easy scanning of old roomeventid_timestamp records for
/// removal. Be careful with u64, it can have 0xff and 0xfe bytes.
/// A simple split on 0xff will not work with this key. Instead,
/// it is meant to be split on the first 0xff byte only, and
/// separated into room ID and timestamp.
pub(in crate::db) roomtimestamp_eventid: Tree,
}
/// An enum that can hold either a regular sled Tree, or a
/// Transactional tree.
#[derive(Clone, Copy)]
enum TxableTree<'a> {
Tree(&'a Tree),
@ -35,39 +57,107 @@ impl<'a> Into<TxableTree<'a>> for &'a TransactionalTree {
}
}
fn get_set<'a, T: Into<TxableTree<'a>>>(tree: T, key: &[u8]) -> Result<HashSet<String>, DataError> {
let set: HashSet<String> = match tree.into() {
TxableTree::Tree(tree) => tree.get(key)?,
TxableTree::Tx(tx) => tx.get(key)?,
/// A set of functions that can be used with a sled::Tree that stores
/// HashSets as its values. Atomicity is partially handled. If the
/// Tree is a transactional tree, operations will be atomic.
/// Otherwise, there is a potential non-atomic step.
mod hashset_tree {
projectmoon marked this conversation as resolved
Review

Perhaps move this and TxableTree into a common part of the database code. Maybe also convert it to a trait. The atomicity issues with Tree instances also should be addressed. Use fetch_and_update when it's a regular Tree, and the existing code if it's a TransactionalTree (since the atomicity is controlled by the transaction).

Perhaps move this and `TxableTree` into a common part of the database code. Maybe also convert it to a trait. The atomicity issues with `Tree` instances also should be addressed. Use `fetch_and_update` when it's a regular Tree, and the existing code if it's a `TransactionalTree` (since the atomicity is controlled by the transaction).
Review

Deferring to a future changeset.

Deferring to a future changeset.
use super::*;
fn insert_set<'a, T: Into<TxableTree<'a>>>(
tree: T,
key: &[u8],
set: HashSet<String>,
) -> Result<(), DataError> {
let serialized = bincode::serialize(&set)?;
match tree.into() {
TxableTree::Tree(tree) => tree.insert(key, serialized)?,
TxableTree::Tx(tx) => tx.insert(key, serialized)?,
};
Ok(())
}
.map(|bytes| bincode::deserialize::<HashSet<String>>(&bytes))
.unwrap_or(Ok(HashSet::new()))?;
Ok(set)
pub(super) fn get_set<'a, T: Into<TxableTree<'a>>>(
tree: T,
key: &[u8],
) -> Result<HashSet<String>, DataError> {
let set: HashSet<String> = match tree.into() {
TxableTree::Tree(tree) => tree.get(key)?,
TxableTree::Tx(tx) => tx.get(key)?,
}
.map(|bytes| bincode::deserialize::<HashSet<String>>(&bytes))
.unwrap_or(Ok(HashSet::new()))?;
Ok(set)
}
pub(super) fn remove_from_set<'a, T: Into<TxableTree<'a>> + Copy>(
tree: T,
key: &[u8],
value_to_remove: &str,
) -> Result<(), DataError> {
let mut set = get_set(tree, key)?;
set.remove(value_to_remove);
insert_set(tree, key, set)?;
Ok(())
}
pub(super) fn add_to_set<'a, T: Into<TxableTree<'a>> + Copy>(
tree: T,
key: &[u8],
value_to_add: String,
) -> Result<(), DataError> {
let mut set = get_set(tree, key)?;
set.insert(value_to_add);
insert_set(tree, key, set)?;
Ok(())
}
}
fn remove_from_set<'a, T: Into<TxableTree<'a>> + Copy>(
tree: T,
key: &[u8],
value_to_remove: &str,
) -> Result<(), DataError> {
let mut set = get_set(tree, key)?;
set.remove(value_to_remove);
insert_set(tree, key, set)?;
Ok(())
}
/// Functions that specifically relate to the "timestamp index" tree,
/// which is stored on the Room sinstance as a tree called
/// roomtimestamp_eventid. Tightly coupled to the event watcher in the
/// Rooms impl, and only factored out for unit testing.
mod timestamp_index {
use super::*;
fn insert_set<'a, T: Into<TxableTree<'a>>>(
tree: T,
key: &[u8],
set: HashSet<String>,
) -> Result<(), DataError> {
let serialized = bincode::serialize(&set)?;
match tree.into() {
TxableTree::Tree(tree) => tree.insert(key, serialized)?,
TxableTree::Tx(tx) => tx.insert(key, serialized)?,
};
Ok(())
/// Insert an entry from the main roomeventid_timestamp Tree into
/// the timestamp index. Keys in this Tree are stored as room ID
/// 0xff timestamp, with the value being a hashset of event IDs
/// received at the time. The parameters come from an insert to
/// that Tree, where the key is room ID 0xff event ID, and the
/// value is the timestamp.
pub(super) fn insert(
roomtimestamp_eventid: &Tree,
key: &[u8],
timestamp_bytes: &[u8],
) -> Result<(), DataError> {
let parts: Vec<&[u8]> = key.split(|&b| b == 0xff).collect();
if let [room_id, event_id] = parts[..] {
let mut ts_key = room_id.to_vec();
ts_key.push(0xff);
ts_key.extend_from_slice(&timestamp_bytes);
trace_index_record(room_id, event_id, &timestamp_bytes);
let event_id = str::from_utf8(event_id)?;
hashset_tree::add_to_set(roomtimestamp_eventid, &ts_key, event_id.to_owned())?;
Ok(())
} else {
Err(DataError::InvalidValue)
}
}
/// Log a trace message.
fn trace_index_record(room_id: &[u8], event_id: &[u8], timestamp: &[u8]) {
if log_enabled!(log::Level::Trace) {
trace!(
"Recording event {} | {} received at {} in timestamp index.",
str::from_utf8(room_id).unwrap_or("[invalid room id]"),
str::from_utf8(event_id).unwrap_or("[invalid event id]"),
convert_u64(timestamp).unwrap_or(0)
);
}
}
}
impl Rooms {
@ -76,29 +166,81 @@ impl Rooms {
roomid_roominfo: db.open_tree("roomid_roominfo")?,
roomid_usernames: db.open_tree("roomid_usernames")?,
username_roomids: db.open_tree("username_roomids")?,
roomeventid_timestamp: db.open_tree("roomeventid_timestamp")?,
roomtimestamp_eventid: db.open_tree("roomtimestamp_eventid")?,
})
}
/// Start an event subscriber that listens for inserts made by the
/// `should_process` function. This event handler duplicates the
/// entry by timestamp instead of event ID.
pub(in crate::db) fn start_handler(&self) -> JoinHandle<()> {
//Clone due to lifetime requirements.
let roomeventid_timestamp = self.roomeventid_timestamp.clone();
let roomtimestamp_eventid = self.roomtimestamp_eventid.clone();
tokio::spawn(async move {
let mut subscriber = roomeventid_timestamp.watch_prefix(b"");
// TODO make this handler receive kill messages somehow so
// we can unit test it and gracefully shut it down.
while let Some(event) = (&mut subscriber).await {
if let sled::Event::Insert { key, value } = event {
match timestamp_index::insert(&roomtimestamp_eventid, &key, &value) {
Err(e) => {
error!("Unable to update the timestamp index: {}", e);
}
_ => (),
}
}
}
})
}
/// Determine if an event in a room should be processed. The event
/// is atomically recorded and true returned if the database has
/// not seen tis event yet. If the event already exists in the
/// database, the function returns false. Events are recorded by
/// this function by inserting the (system-local) timestamp in
/// epoch seconds.
pub fn should_process(&self, room_id: &str, event_id: &str) -> Result<bool, DataError> {
let mut key = room_id.as_bytes().to_vec();
key.push(0xff);
key.extend_from_slice(event_id.as_bytes());
let timestamp: U64<BigEndian> = U64::new(
SystemTime::now()
.duration_since(UNIX_EPOCH)
.expect("Clock has gone backwards")
.as_secs(),
);
match self.roomeventid_timestamp.compare_and_swap(
key,
None as Option<&[u8]>,
Some(timestamp.as_bytes()),
)? {
Ok(()) => Ok(true),
Err(CompareAndSwapError { .. }) => Ok(false),
}
}
pub fn get_rooms_for_user(&self, username: &str) -> Result<HashSet<String>, DataError> {
get_set(&self.username_roomids, username.as_bytes())
hashset_tree::get_set(&self.username_roomids, username.as_bytes())
}
pub fn get_users_in_room(&self, room_id: &str) -> Result<HashSet<String>, DataError> {
get_set(&self.roomid_usernames, room_id.as_bytes())
hashset_tree::get_set(&self.roomid_usernames, room_id.as_bytes())
}
pub fn add_user_to_room(&self, username: &str, room_id: &str) -> Result<(), DataError> {
(&self.username_roomids, &self.roomid_usernames).transaction(
|(tx_username_rooms, tx_room_usernames)| {
let username_key = &username.as_bytes();
let mut user_to_rooms = get_set(tx_username_rooms, username_key)?;
user_to_rooms.insert(room_id.to_string());
insert_set(tx_username_rooms, username_key, user_to_rooms)?;
hashset_tree::add_to_set(tx_username_rooms, username_key, room_id.to_owned())?;
let roomid_key = &room_id.as_bytes();
let mut room_to_users = get_set(tx_room_usernames, roomid_key)?;
room_to_users.insert(username.to_string());
insert_set(tx_room_usernames, roomid_key, room_to_users)?;
hashset_tree::add_to_set(tx_room_usernames, roomid_key, username.to_owned())?;
Ok(())
},
@ -111,14 +253,10 @@ impl Rooms {
(&self.username_roomids, &self.roomid_usernames).transaction(
|(tx_username_rooms, tx_room_usernames)| {
let username_key = &username.as_bytes();
let mut user_to_rooms = get_set(tx_username_rooms, username_key)?;
user_to_rooms.remove(room_id);
insert_set(tx_username_rooms, username_key, user_to_rooms)?;
hashset_tree::remove_from_set(tx_username_rooms, username_key, room_id)?;
let roomid_key = &room_id.as_bytes();
let mut room_to_users = get_set(tx_room_usernames, roomid_key)?;
room_to_users.remove(username);
insert_set(tx_room_usernames, roomid_key, room_to_users)?;
hashset_tree::remove_from_set(tx_room_usernames, roomid_key, username)?;
Ok(())
},
@ -131,11 +269,15 @@ impl Rooms {
(&self.username_roomids, &self.roomid_usernames).transaction(
|(tx_username_roomids, tx_roomid_usernames)| {
let roomid_key = room_id.as_bytes();
let users_in_room = get_set(tx_roomid_usernames, roomid_key)?;
let users_in_room = hashset_tree::get_set(tx_roomid_usernames, roomid_key)?;
//Remove the room ID from every user's room ID list.
for username in users_in_room {
remove_from_set(tx_username_roomids, username.as_bytes(), room_id)?;
hashset_tree::remove_from_set(
tx_username_roomids,
username.as_bytes(),
room_id,
)?;
}
//Remove this room entry for the room ID -> username tree.
@ -164,6 +306,7 @@ mod tests {
#[test]
fn add_user_to_room() {
let rooms = create_test_instance();
rooms
.add_user_to_room("testuser", "myroom")
.expect("Could not add user to room");
@ -189,6 +332,7 @@ mod tests {
#[test]
fn remove_user_from_room() {
let rooms = create_test_instance();
rooms
.add_user_to_room("testuser", "myroom")
.expect("Could not add user to room");
@ -212,6 +356,7 @@ mod tests {
#[test]
fn clear_info() {
let rooms = create_test_instance();
rooms
.add_user_to_room("testuser", "myroom1")
.expect("Could not add user to room1");
@ -246,4 +391,37 @@ mod tests {
assert_eq!(expected_users_in_room2, users_in_room2);
assert_eq!(expected_rooms_for_user, rooms_for_user);
}
#[test]
fn insert_to_timestamp_index() {
let rooms = create_test_instance();
// Insertion into timestamp index based on data that would go
// into main room x eventID -> timestamp tree.
let mut key = b"myroom".to_vec();
key.push(0xff);
key.extend_from_slice(b"myeventid");
let timestamp: U64<BigEndian> = U64::new(1000);
let result = timestamp_index::insert(
&rooms.roomtimestamp_eventid,
key.as_bytes(),
timestamp.as_bytes(),
);
assert!(result.is_ok());
// Retrieval of data from the timestamp index tree.
let mut ts_key = b"myroom".to_vec();
ts_key.push(0xff);
ts_key.extend_from_slice(timestamp.as_bytes());
let expected_events: HashSet<String> =
vec![String::from("myeventid")].into_iter().collect();
let event_ids = hashset_tree::get_set(&rooms.roomtimestamp_eventid, &ts_key)
.expect("Could not get set out of Tree");
assert_eq!(expected_events, event_ids);
}
}

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@ -1,6 +1,6 @@
use crate::db::errors::DataError;
use byteorder::LittleEndian;
use zerocopy::byteorder::{I32, U32};
use byteorder::{BigEndian, LittleEndian};
use zerocopy::byteorder::{I32, U32, U64};
use zerocopy::LayoutVerified;
/// User variables are stored as little-endian 32-bit integers in the
@ -10,6 +10,11 @@ type LittleEndianI32Layout<'a> = LayoutVerified<&'a [u8], I32<LittleEndian>>;
type LittleEndianU32Layout<'a> = LayoutVerified<&'a [u8], U32<LittleEndian>>;
#[allow(dead_code)]
type LittleEndianU64Layout<'a> = LayoutVerified<&'a [u8], U64<LittleEndian>>;
type BigEndianU64Layout<'a> = LayoutVerified<&'a [u8], U64<BigEndian>>;
/// Convert bytes to an i32 with zero-copy deserialization. An error
/// is returned if the bytes do not represent an i32.
pub(super) fn convert_i32(raw_value: &[u8]) -> Result<i32, DataError> {
@ -33,3 +38,15 @@ pub(super) fn convert_u32(raw_value: &[u8]) -> Result<u32, DataError> {
Err(DataError::I32SchemaViolation)
}
}
#[allow(dead_code)]
pub(super) fn convert_u64(raw_value: &[u8]) -> Result<u64, DataError> {
let layout = BigEndianU64Layout::new_unaligned(raw_value.as_ref());
if let Some(layout) = layout {
let value: U64<BigEndian> = *layout;
Ok(value.get())
} else {
Err(DataError::I32SchemaViolation)
}
}