From e0221fc0a3a619ea53e83a336f66600034a7799a Mon Sep 17 00:00:00 2001
From: Tamo <tamo@meilisearch.com>
Date: Mon, 17 Oct 2022 13:11:12 +0200
Subject: [PATCH] fix a synchronization bug while importing tasks

---
 index-scheduler/src/lib.rs  |  1 +
 meilisearch-http/src/lib.rs | 27 +++++++++++++++------------
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/index-scheduler/src/lib.rs b/index-scheduler/src/lib.rs
index ddf75b2a8..a65fa8bcd 100644
--- a/index-scheduler/src/lib.rs
+++ b/index-scheduler/src/lib.rs
@@ -534,6 +534,7 @@ impl IndexScheduler {
     pub fn create_update_file(&self) -> Result<(Uuid, file_store::File)> {
         Ok(self.file_store.new_update()?)
     }
+
     #[cfg(test)]
     pub fn create_update_file_with_uuid(&self, uuid: u128) -> Result<(Uuid, file_store::File)> {
         Ok(self.file_store.new_update_with_uuid(uuid)?)
diff --git a/meilisearch-http/src/lib.rs b/meilisearch-http/src/lib.rs
index f853dbe69..fb6c6497e 100644
--- a/meilisearch-http/src/lib.rs
+++ b/meilisearch-http/src/lib.rs
@@ -196,15 +196,12 @@ fn import_dump(
         keys.push(key);
     }
 
-    // 3. Import the tasks.
-    for ret in dump_reader.tasks() {
-        let (task, file) = ret?;
-        index_scheduler.register_dumpped_task(task, file, &keys, instance_uid)?;
-    }
+    let indexer_config = index_scheduler.indexer_config().clone();
 
-    let indexer_config = index_scheduler.indexer_config();
+    // /!\ The tasks must be imported AFTER importing the indexes or else the scheduler might
+    // try to process tasks while we're trying to import the indexes.
 
-    // 4. Import the indexes.
+    // 3. Import the indexes.
     for index_reader in dump_reader.indexes()? {
         let mut index_reader = index_reader?;
         let metadata = index_reader.metadata();
@@ -214,12 +211,12 @@ fn import_dump(
         let mut wtxn = index.write_txn()?;
 
         let mut builder = milli::update::Settings::new(&mut wtxn, &index, indexer_config);
-        // 4.1 Import the primary key if there is one.
+        // 3.1 Import the primary key if there is one.
         if let Some(ref primary_key) = metadata.primary_key {
             builder.set_primary_key(primary_key.to_string());
         }
 
-        // 4.2 Import the settings.
+        // 3.2 Import the settings.
         log::info!("Importing the settings.");
         let settings = index_reader.settings()?;
         apply_settings_to_builder(&settings, &mut builder);
@@ -227,8 +224,8 @@ fn import_dump(
             log::debug!("update: {:?}", indexing_step);
         })?;
 
-        // 4.3 Import the documents.
-        // 4.3.1 We need to recreate the grenad+obkv format accepted by the index.
+        // 3.3 Import the documents.
+        // 3.3.1 We need to recreate the grenad+obkv format accepted by the index.
         log::info!("Importing the documents.");
         let mut file = tempfile::tempfile()?;
         let mut builder = DocumentsBatchBuilder::new(BufWriter::new(&mut file));
@@ -237,7 +234,7 @@ fn import_dump(
         }
         builder.into_inner()?; // this actually flush the content of the batch builder.
 
-        // 4.3.2 We feed it to the milli index.
+        // 3.3.2 We feed it to the milli index.
         file.seek(SeekFrom::Start(0))?;
         let reader = BufReader::new(file);
         let reader = DocumentsBatchReader::from_reader(reader)?;
@@ -259,6 +256,12 @@ fn import_dump(
         wtxn.commit()?;
         log::info!("All documents successfully imported.");
     }
+
+    // 4. Import the tasks.
+    for ret in dump_reader.tasks() {
+        let (task, file) = ret?;
+        index_scheduler.register_dumpped_task(task, file, &keys, instance_uid)?;
+    }
     Ok(())
 }