bug(lib): drop env on last use

fixes the `too many open files` error when running tests by closing the
environment on last drop

meilisearch-lib/src/index_resolver/meta_store.rs

@@ -2,6 +2,7 @@ use std::collections::HashSet;
 use std::fs::{create_dir_all, File};
 use std::io::{BufRead, BufReader, Write};
 use std::path::{Path, PathBuf};
+use std::sync::Arc;
 
 use heed::types::{SerdeBincode, Str};
 use heed::{CompactionOption, Database, Env};
@@ -42,12 +43,20 @@ pub struct IndexMeta {
 
 #[derive(Clone)]
 pub struct HeedMetaStore {
-    env: Env,
+    env: Arc<Env>,
     db: Database<Str, SerdeBincode<IndexMeta>>,
 }
 
+impl Drop for HeedMetaStore {
+    fn drop(&mut self) {
+        if Arc::strong_count(&self.env) == 1 {
+            self.env.as_ref().clone().prepare_for_closing();
+        }
+    }
+}
+
 impl HeedMetaStore {
-    pub fn new(env: heed::Env) -> Result<Self> {
+    pub fn new(env: Arc<heed::Env>) -> Result<Self> {
         let db = env.create_database(Some("uuids"))?;
         Ok(Self { env, db })
     }
@@ -144,7 +153,7 @@ impl HeedMetaStore {
         Ok(())
     }
 
-    pub fn load_dump(src: impl AsRef<Path>, env: heed::Env) -> Result<()> {
+    pub fn load_dump(src: impl AsRef<Path>, env: Arc<heed::Env>) -> Result<()> {
         let src_indexes = src.as_ref().join(UUIDS_DB_PATH).join("data.jsonl");
         let indexes = File::open(&src_indexes)?;
         let mut indexes = BufReader::new(indexes);

meilisearch-lib/src/index_resolver/mod.rs

@@ -4,6 +4,7 @@ pub mod meta_store;
 
 use std::convert::TryInto;
 use std::path::Path;
+use std::sync::Arc;
 
 use chrono::Utc;
 use error::{IndexResolverError, Result};
@@ -16,13 +17,11 @@ use serde::{Deserialize, Serialize};
 use tokio::task::spawn_blocking;
 use uuid::Uuid;
 
-use crate::index::update_handler::UpdateHandler;
-use crate::index::{error::Result as IndexResult, Index};
+use crate::index::{error::Result as IndexResult, update_handler::UpdateHandler, Index};
 use crate::options::IndexerOpts;
 use crate::tasks::batch::Batch;
 use crate::tasks::task::{DocumentDeletion, Job, Task, TaskContent, TaskEvent, TaskId, TaskResult};
-use crate::tasks::Pending;
-use crate::tasks::TaskPerformer;
+use crate::tasks::{Pending, TaskPerformer};
 use crate::update_file_store::UpdateFileStore;
 
 use self::meta_store::IndexMeta;
@@ -39,7 +38,7 @@ pub fn create_index_resolver(
     path: impl AsRef<Path>,
     index_size: usize,
     indexer_opts: &IndexerOpts,
-    meta_env: heed::Env,
+    meta_env: Arc<heed::Env>,
     file_store: UpdateFileStore,
 ) -> anyhow::Result<HardStateIndexResolver> {
     let uuid_store = HeedMetaStore::new(meta_env)?;
@@ -153,7 +152,7 @@ impl IndexResolver<HeedMetaStore, MapIndexStore> {
         src: impl AsRef<Path>,
         dst: impl AsRef<Path>,
         index_db_size: usize,
-        env: Env,
+        env: Arc<Env>,
         indexer_opts: &IndexerOpts,
     ) -> anyhow::Result<()> {
         HeedMetaStore::load_dump(&src, env)?;