Merge #5107

5107: While spamming the batches route we could see a processing batch becoming missing and then finished, this commit ensures the batches goes from processing to finished directly r=irevoire a=irevoire

# Pull Request

## Related issue
Fixes the failed tests from this PR: https://github.com/meilisearch/meilisearch-js/pull/1775
See [this message](https://meilisearch.slack.com/archives/CD7Q2UKGB/p1732784680450749) [private link] for more context

## What does this PR do?
- Ensure we never enter a state where a processing batches (only existing in RAM) becomes « Not found » by removing the processing batches AFTER writing them to disk
- This should also theoretically avoid an issue where a task could go from processing to enqueued and then finished


Co-authored-by: Tamo <tamo@meilisearch.com>

crates/index-scheduler/src/lib.rs

@@ -1738,11 +1738,8 @@ impl IndexScheduler {
             }
         }
 
-        self.processing_tasks.write().unwrap().stop_processing();
         // We must re-add the canceled task so they're part of the same batch.
-        // processed.processing |= canceled;
         ids |= canceled;
-
         self.write_batch(&mut wtxn, processing_batch, &ids)?;
 
         #[cfg(test)]
@@ -1750,6 +1747,10 @@ impl IndexScheduler {
 
         wtxn.commit().map_err(Error::HeedTransaction)?;
 
+        // We should stop processing AFTER everything is processed and written to disk otherwise, a batch (which only lives in RAM) may appear in the processing task
+        // and then become « not found » for some time until the commit everything is written and the final commit is made.
+        self.processing_tasks.write().unwrap().stop_processing();
+
         // Once the tasks are committed, we should delete all the update files associated ASAP to avoid leaking files in case of a restart
         tracing::debug!("Deleting the update files");
 

crates/meilisearch/tests/batches/mod.rs

@@ -224,7 +224,7 @@ async fn list_batches_status_and_type_filtered() {
 }
 
 #[actix_rt::test]
-async fn get_batch_filter_error() {
+async fn list_batch_filter_error() {
     let server = Server::new().await;
 
     let (response, code) = server.batches_filter("lol=pied").await;