implement index deletion

src/data/updates.rs

@@ -82,6 +82,15 @@ impl Data {
         Ok(update.into())
     }
 
+    pub async fn delete_index(
+        &self,
+        index: impl AsRef<str> + Send + Sync + 'static,
+    ) -> anyhow::Result<()> {
+        let index_controller = self.index_controller.clone();
+        tokio::task::spawn_blocking(move || { index_controller.delete_index(index) }).await??;
+        Ok(())
+    }
+
     #[inline]
     pub fn get_update_status(&self, index: impl AsRef<str>, uid: u64) -> anyhow::Result<Option<UpdateStatus>> {
         self.index_controller.update_status(index, uid)

src/index_controller/local_index_controller/index_store.rs

@@ -1,3 +1,4 @@
+use std::time::Duration;
 use std::fs::{create_dir_all, remove_dir_all};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
@@ -6,7 +7,7 @@ use anyhow::{bail, Context};
 use chrono::{DateTime, Utc};
 use dashmap::{DashMap, mapref::entry::Entry};
 use heed::{Env, EnvOpenOptions, Database, types::{Str, SerdeJson, ByteSlice}, RoTxn, RwTxn};
-use log::error;
+use log::{error, info};
 use milli::Index;
 use rayon::ThreadPool;
 use serde::{Serialize, Deserialize};
@@ -90,6 +91,52 @@ impl IndexStore {
         })
     }
 
+    pub fn delete(&self, index_uid: impl AsRef<str>) -> anyhow::Result<()> {
+        // we remove the references to the index from the index map so it is not accessible anymore
+        let mut txn = self.env.write_txn()?;
+        let uuid = self.index_uuid(&txn, &index_uid)?
+            .with_context(|| format!("Index {:?} doesn't exist", index_uid.as_ref()))?;
+        self.name_to_uuid.delete(&mut txn, index_uid.as_ref())?;
+        self.uuid_to_index_meta.delete(&mut txn, uuid.as_bytes())?;
+        txn.commit()?;
+        // If the index was loaded, we need to close it. Since we already removed references to it
+        // from the index_store, the only that can still get a reference to it is the update store.
+        //
+        // First, we want to remove any pending updates from the store.
+        // Second, we try to get ownership on the update store so we can close it. It may take a
+        // couple of tries, but since the update store event loop only has a weak reference to
+        // itself, and we are the only other function holding a reference to it otherwise, we will
+        // get it eventually.
+        // Fourth, we request a closing of the update store.
+        // Fifth, we can take ownership on the index, and close it.
+        // Lastly, remove all the files from the file system.
+        let index_uid = index_uid.as_ref().to_string();
+        if let Some((_, (index, updates))) = self.uuid_to_index.remove(&uuid) {
+            std::thread::spawn(move || {
+                info!("Preparing for {:?} deletion.", index_uid);
+                // this error is non fatal, but may delay the deletion.
+                if let Err(e) = updates.abort_pendings() {
+                    error!(
+                        "error aborting pending updates when deleting index {:?}: {}",
+                        index_uid,
+                        e
+                    );
+                }
+                let updates = get_arc_ownership_blocking(updates);
+                let close_event = updates.prepare_for_closing();
+                close_event.wait();
+                info!("closed update store for {:?}", index_uid);
+
+                let index = get_arc_ownership_blocking(index);
+                let close_event = index.prepare_for_closing();
+                close_event.wait();
+                info!("index {:?} deleted.", index_uid);
+            });
+        }
+
+        Ok(())
+    }
+
     fn index_uuid(&self, txn: &RoTxn, name: impl AsRef<str>) -> anyhow::Result<Option<Uuid>> {
         match self.name_to_uuid.get(txn, name.as_ref())? {
             Some(bytes) => {
@@ -299,6 +346,20 @@ impl IndexStore {
     }
 }
 
+// Loops on an arc to get ownership on the wrapped value. This method sleeps 100ms before retrying.
+fn get_arc_ownership_blocking<T>(mut item: Arc<T>) -> T {
+    loop {
+        match Arc::try_unwrap(item) {
+            Ok(item) => return item,
+            Err(item_arc) => {
+                item = item_arc;
+                std::thread::sleep(Duration::from_millis(100));
+                continue;
+            }
+        }
+    }
+}
+
 fn open_or_create_database<K: 'static, V: 'static>(env: &Env, name: Option<&str>) -> anyhow::Result<Database<K, V>> {
     match env.open_database::<K, V>(name)? {
         Some(db) => Ok(db),

src/index_controller/local_index_controller/mod.rs

@@ -80,8 +80,8 @@ impl IndexController for LocalIndexController {
         Ok(meta)
     }
 
-    fn delete_index<S: AsRef<str>>(&self, _index_uid: S) -> anyhow::Result<()> {
+    fn delete_index<S: AsRef<str>>(&self, index_uid: S) -> anyhow::Result<()> {
-        todo!()
+        self.indexes.delete(index_uid)
     }
 
     fn swap_indices<S1: AsRef<str>, S2: AsRef<str>>(&self, _index1_uid: S1, _index2_uid: S2) -> anyhow::Result<()> {

src/index_controller/local_index_controller/update_store.rs

@@ -66,23 +66,37 @@ where
             processing,
         });
 
-        let update_store_cloned = update_store.clone();
+        // We need a week reference so we can take ownership on the arc later when we
+        // want to close the index.
+        let update_store_weak = Arc::downgrade(&update_store);
         std::thread::spawn(move || {
             // Block and wait for something to process.
-            for () in notification_receiver {
+            'outer: for _ in notification_receiver {
                 loop {
-                    match update_store_cloned.process_pending_update(&mut update_handler) {
+                    match update_store_weak.upgrade() {
+                        Some(update_store) => {
+                            match update_store.process_pending_update(&mut update_handler) {
                                 Ok(Some(_)) => (),
                                 Ok(None) => break,
                                 Err(e) => eprintln!("error while processing update: {}", e),
                             }
                         }
+                        // the ownership on the arc has been taken, we need to exit
+                        None => break 'outer,
+                    }
+                }
             }
         });
 
         Ok(update_store)
     }
 
+    pub fn prepare_for_closing(self) -> heed::EnvClosingEvent {
+        // We ignore this error, since that would mean the event loop is already closed.
+        let closing_event = self.env.prepare_for_closing();
+        closing_event
+    }
+
     /// Returns the new biggest id to use to store the new update.
     fn new_update_id(&self, txn: &heed::RoTxn) -> heed::Result<u64> {
         let last_pending = self.pending_meta

src/routes/index.rs

@@ -108,10 +108,16 @@ async fn update_index(
 
 #[delete("/indexes/{index_uid}", wrap = "Authentication::Private")]
 async fn delete_index(
-    _data: web::Data<Data>,
+    data: web::Data<Data>,
-    _path: web::Path<IndexParam>,
+    path: web::Path<IndexParam>,
 ) -> Result<HttpResponse, ResponseError> {
+    match data.delete_index(path.index_uid.clone()).await {
+        Ok(_) => Ok(HttpResponse::Ok().finish()),
+        Err(e) => {
+            error!("{}", e);
             todo!()
+        }
+    }
 }
 
 #[derive(Deserialize)]