use std::collections::hash_map::Entry; use std::collections::HashMap; use std::path::PathBuf; use std::sync::{Arc, RwLock}; use std::{fs, thread}; use log::error; use meilisearch_types::heed::types::{SerdeBincode, Str}; use meilisearch_types::heed::{Database, Env, EnvOpenOptions, RoTxn, RwTxn}; use meilisearch_types::milli::update::IndexerConfig; use meilisearch_types::milli::Index; use uuid::Uuid; use self::IndexStatus::{Available, BeingDeleted}; use crate::{Error, Result}; const INDEX_MAPPING: &str = "index-mapping"; /// Structure managing meilisearch's indexes. /// /// It is responsible for: /// 1. Creating new indexes /// 2. Opening indexes and storing references to these opened indexes /// 3. Accessing indexes through their uuid /// 4. Mapping a user-defined name to each index uuid. #[derive(Clone)] pub struct IndexMapper { /// Keep track of the opened indexes. Used mainly by the index resolver. index_map: Arc>>, // TODO create a UUID Codec that uses the 16 bytes representation /// Map an index name with an index uuid currently available on disk. index_mapping: Database>, /// Path to the folder where the LMDB environments of each index are. base_path: PathBuf, index_size: usize, pub indexer_config: Arc, } /// Whether the index is available for use or is forbidden to be inserted back in the index map #[derive(Clone)] pub enum IndexStatus { /// Do not insert it back in the index map as it is currently being deleted. BeingDeleted, /// You can use the index without worrying about anything. Available(Index), } impl IndexMapper { pub fn new( env: &Env, base_path: PathBuf, index_size: usize, indexer_config: IndexerConfig, ) -> Result { Ok(Self { index_map: Arc::default(), index_mapping: env.create_database(Some(INDEX_MAPPING))?, base_path, index_size, indexer_config: Arc::new(indexer_config), }) } /// Get or create the index. pub fn create_index(&self, wtxn: &mut RwTxn, name: &str) -> Result { match self.index(wtxn, name) { Ok(index) => Ok(index), Err(Error::IndexNotFound(_)) => { let uuid = Uuid::new_v4(); self.index_mapping.put(wtxn, name, &uuid)?; let index_path = self.base_path.join(uuid.to_string()); fs::create_dir_all(&index_path)?; let mut options = EnvOpenOptions::new(); options.map_size(self.index_size); options.max_readers(1024); Ok(Index::new(options, &index_path)?) } error => error, } } /// Removes the index from the mapping table and the in-memory index map /// but keeps the associated tasks. pub fn delete_index(&self, mut wtxn: RwTxn, name: &str) -> Result<()> { let uuid = self .index_mapping .get(&wtxn, name)? .ok_or_else(|| Error::IndexNotFound(name.to_string()))?; // Once we retrieved the UUID of the index we remove it from the mapping table. assert!(self.index_mapping.delete(&mut wtxn, name)?); wtxn.commit()?; // We remove the index from the in-memory index map. let mut lock = self.index_map.write().unwrap(); let closing_event = match lock.insert(uuid, BeingDeleted) { Some(Available(index)) => Some(index.prepare_for_closing()), _ => None, }; drop(lock); let index_map = self.index_map.clone(); let index_path = self.base_path.join(uuid.to_string()); let index_name = name.to_string(); thread::spawn(move || { // We first wait to be sure that the previously opened index is effectively closed. // This can take a lot of time, this is why we do that in a seperate thread. if let Some(closing_event) = closing_event { closing_event.wait(); } // Then we remove the content from disk. if let Err(e) = fs::remove_dir_all(&index_path) { error!( "An error happened when deleting the index {} ({}): {}", index_name, uuid, e ); } // Finally we remove the entry from the index map. assert!(matches!(index_map.write().unwrap().remove(&uuid), Some(BeingDeleted))); }); Ok(()) } pub fn exists(&self, rtxn: &RoTxn, name: &str) -> Result { Ok(self.index_mapping.get(rtxn, name)?.is_some()) } /// Return an index, may open it if it wasn't already opened. pub fn index(&self, rtxn: &RoTxn, name: &str) -> Result { let uuid = self .index_mapping .get(rtxn, name)? .ok_or_else(|| Error::IndexNotFound(name.to_string()))?; // we clone here to drop the lock before entering the match let index = self.index_map.read().unwrap().get(&uuid).cloned(); let index = match index { Some(Available(index)) => index, Some(BeingDeleted) => return Err(Error::IndexNotFound(name.to_string())), // since we're lazy, it's possible that the index has not been opened yet. None => { let mut index_map = self.index_map.write().unwrap(); // between the read lock and the write lock it's not impossible // that someone already opened the index (eg if two search happens // at the same time), thus before opening it we check a second time // if it's not already there. // Since there is a good chance it's not already there we can use // the entry method. match index_map.entry(uuid) { Entry::Vacant(entry) => { let index_path = self.base_path.join(uuid.to_string()); fs::create_dir_all(&index_path)?; let mut options = EnvOpenOptions::new(); options.map_size(self.index_size); let index = Index::new(options, &index_path)?; entry.insert(Available(index.clone())); index } Entry::Occupied(entry) => match entry.get() { Available(index) => index.clone(), BeingDeleted => return Err(Error::IndexNotFound(name.to_string())), }, } } }; Ok(index) } /// Return all indexes, may open them if they weren't already opened. pub fn indexes(&self, rtxn: &RoTxn) -> Result> { self.index_mapping .iter(rtxn)? .map(|ret| { ret.map_err(Error::from).and_then(|(name, _)| { self.index(rtxn, name).map(|index| (name.to_string(), index)) }) }) .collect() } /// Swap two index names. pub fn swap(&self, wtxn: &mut RwTxn, lhs: &str, rhs: &str) -> Result<()> { let lhs_uuid = self .index_mapping .get(wtxn, lhs)? .ok_or_else(|| Error::IndexNotFound(lhs.to_string()))?; let rhs_uuid = self .index_mapping .get(wtxn, rhs)? .ok_or_else(|| Error::IndexNotFound(rhs.to_string()))?; self.index_mapping.put(wtxn, lhs, &rhs_uuid)?; self.index_mapping.put(wtxn, rhs, &lhs_uuid)?; Ok(()) } pub fn index_exists(&self, rtxn: &RoTxn, name: &str) -> Result { Ok(self.index_mapping.get(rtxn, name)?.is_some()) } pub fn indexer_config(&self) -> &IndexerConfig { &self.indexer_config } }