From caa231aebe6692a79bb3ef5c2c03c887cba5e558 Mon Sep 17 00:00:00 2001
From: marin postma <postma.marin@protonmail.com>
Date: Wed, 16 Jun 2021 14:52:06 +0200
Subject: [PATCH] fix race condition

---
 meilisearch-http/src/index_controller/mod.rs    | 17 +++++++++++++++--
 .../index_controller/update_actor/store/mod.rs  | 13 ++++++++++---
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/meilisearch-http/src/index_controller/mod.rs b/meilisearch-http/src/index_controller/mod.rs
index b51a6c5b0..313709e21 100644
--- a/meilisearch-http/src/index_controller/mod.rs
+++ b/meilisearch-http/src/index_controller/mod.rs
@@ -6,6 +6,7 @@ use std::time::Duration;
 use actix_web::web::{Bytes, Payload};
 use chrono::{DateTime, Utc};
 use futures::stream::StreamExt;
+use log::error;
 use log::info;
 use milli::FieldsDistribution;
 use serde::{Deserialize, Serialize};
@@ -256,8 +257,20 @@ impl IndexController {
 
     pub async fn delete_index(&self, uid: String) -> Result<()> {
         let uuid = self.uuid_resolver.delete(uid).await?;
-        self.update_handle.delete(uuid).await?;
-        self.index_handle.delete(uuid).await?;
+
+        // We remove the index from the resolver synchronously, and effectively perform the index
+        // deletion as a background task.
+        let update_handle = self.update_handle.clone();
+        let index_handle = self.index_handle.clone();
+        tokio::spawn(async move {
+            if let Err(e) = update_handle.delete(uuid).await {
+                error!("Error while deleting index: {}", e);
+            }
+            if let Err(e) = index_handle.delete(uuid).await {
+                error!("Error while deleting index: {}", e);
+            }
+        });
+
         Ok(())
     }
 
diff --git a/meilisearch-http/src/index_controller/update_actor/store/mod.rs b/meilisearch-http/src/index_controller/update_actor/store/mod.rs
index 0bdf53aee..1ee30c99d 100644
--- a/meilisearch-http/src/index_controller/update_actor/store/mod.rs
+++ b/meilisearch-http/src/index_controller/update_actor/store/mod.rs
@@ -428,7 +428,8 @@ impl UpdateStore {
         Ok(None)
     }
 
-    /// Delete all updates for an index from the update store.
+    /// Delete all updates for an index from the update store. If the currently processing update
+    /// is for `index_uuid`, the call will block until the update is terminated.
     pub fn delete_all(&self, index_uuid: Uuid) -> Result<()> {
         let mut txn = self.env.write_txn()?;
         // Contains all the content file paths that we need to be removed if the deletion was successful.
@@ -469,8 +470,14 @@ impl UpdateStore {
                 let _ = remove_file(path);
             });
 
-        // We don't care about the currently processing update, since it will be removed by itself
-        // once its done processing, and we can't abort a running update.
+        // If the currently processing update is from our index, we wait until it is
+        // finished before returning. This ensure that no write to the index occurs after we delete it.
+        if let State::Processing(uuid, _) = *self.state.read() {
+            if uuid == index_uuid {
+                // wait for a write lock, do nothing with it.
+                self.state.write();
+            }
+        }
 
         Ok(())
     }