Merge #3022

3022: Store the `started_at` for a task that is canceled when processing r=irevoire a=Kerollmops

This PR changes the current behavior of the displayed tasks. When a processing task is canceled, the `started_at` date time is kept and displayed to the user. Otherwise, if the task was just enqueued, the `started_at` remains `null`. If a task is processing, the engine is ctrl-c, starts again, and the task becomes enqueued again, so if it is canceled, its `started_at` will be `null`.

You can read more [in this discussion](https://github.com/meilisearch/specifications/pull/195/files#r1009602335).

Co-authored-by: Kerollmops <clement@meilisearch.com>

index-scheduler/src/batch.rs

@@ -41,7 +41,7 @@ use uuid::Uuid;
 
 use crate::autobatcher::{self, BatchKind};
 use crate::utils::{self, swap_index_uid_in_task};
-use crate::{Error, IndexScheduler, Result, TaskId};
+use crate::{Error, IndexScheduler, ProcessingTasks, Result, TaskId};
 
 /// Represents a combination of tasks that can all be processed at the same time.
 ///
@@ -50,15 +50,39 @@ use crate::{Error, IndexScheduler, Result, TaskId};
 /// be processed.
 #[derive(Debug)]
 pub(crate) enum Batch {
-    TaskCancelation(Task),
+    TaskCancelation {
+        /// The task cancelation itself.
+        task: Task,
+        /// The date and time at which the previously processing tasks started.
+        previous_started_at: OffsetDateTime,
+        /// The list of tasks that were processing when this task cancelation appeared.
+        previous_processing_tasks: RoaringBitmap,
+    },
     TaskDeletion(Task),
     SnapshotCreation(Vec<Task>),
     Dump(Task),
-    IndexOperation { op: IndexOperation, must_create_index: bool },
-    IndexCreation { index_uid: String, primary_key: Option<String>, task: Task },
-    IndexUpdate { index_uid: String, primary_key: Option<String>, task: Task },
-    IndexDeletion { index_uid: String, tasks: Vec<Task>, index_has_been_created: bool },
-    IndexSwap { task: Task },
+    IndexOperation {
+        op: IndexOperation,
+        must_create_index: bool,
+    },
+    IndexCreation {
+        index_uid: String,
+        primary_key: Option<String>,
+        task: Task,
+    },
+    IndexUpdate {
+        index_uid: String,
+        primary_key: Option<String>,
+        task: Task,
+    },
+    IndexDeletion {
+        index_uid: String,
+        tasks: Vec<Task>,
+        index_has_been_created: bool,
+    },
+    IndexSwap {
+        task: Task,
+    },
 }
 
 /// A [batch](Batch) that combines multiple tasks operating on an index.
@@ -115,7 +139,7 @@ impl Batch {
     /// Return the task ids associated with this batch.
     pub fn ids(&self) -> Vec<TaskId> {
         match self {
-            Batch::TaskCancelation(task)
+            Batch::TaskCancelation { task, .. }
             | Batch::TaskDeletion(task)
             | Batch::Dump(task)
             | Batch::IndexCreation { task, .. }
@@ -394,9 +418,15 @@ impl IndexScheduler {
 
         // 1. we get the last task to cancel.
         if let Some(task_id) = to_cancel.max() {
-            return Ok(Some(Batch::TaskCancelation(
-                self.get_task(rtxn, task_id)?.ok_or(Error::CorruptedTaskQueue)?,
-            )));
+            // We retrieve the tasks that were processing before this tasks cancelation started.
+            // We must *not* reset the processing tasks before calling this method.
+            let ProcessingTasks { started_at, processing } =
+                &*self.processing_tasks.read().unwrap();
+            return Ok(Some(Batch::TaskCancelation {
+                task: self.get_task(rtxn, task_id)?.ok_or(Error::CorruptedTaskQueue)?,
+                previous_started_at: *started_at,
+                previous_processing_tasks: processing.clone(),
+            }));
         }
 
         // 2. we get the next task to delete
@@ -482,7 +512,7 @@ impl IndexScheduler {
             self.breakpoint(crate::Breakpoint::InsideProcessBatch);
         }
         match batch {
-            Batch::TaskCancelation(mut task) => {
+            Batch::TaskCancelation { mut task, previous_started_at, previous_processing_tasks } => {
                 // 1. Retrieve the tasks that matched the query at enqueue-time.
                 let matched_tasks =
                     if let KindWithContent::TaskCancelation { tasks, query: _ } = &task.kind {
@@ -492,8 +522,13 @@ impl IndexScheduler {
                     };
 
                 let mut wtxn = self.env.write_txn()?;
-                let canceled_tasks_content_uuids =
-                    self.cancel_matched_tasks(&mut wtxn, task.uid, matched_tasks)?;
+                let canceled_tasks_content_uuids = self.cancel_matched_tasks(
+                    &mut wtxn,
+                    task.uid,
+                    matched_tasks,
+                    previous_started_at,
+                    &previous_processing_tasks,
+                )?;
 
                 task.status = Status::Succeeded;
                 match &mut task.details {
@@ -1199,6 +1234,8 @@ impl IndexScheduler {
         wtxn: &mut RwTxn,
         cancel_task_id: TaskId,
         matched_tasks: &RoaringBitmap,
+        previous_started_at: OffsetDateTime,
+        previous_processing_tasks: &RoaringBitmap,
     ) -> Result<Vec<Uuid>> {
         let now = OffsetDateTime::now_utc();
 
@@ -1214,6 +1251,9 @@ impl IndexScheduler {
             if let Some(uuid) = task.content_uuid() {
                 content_files_to_delete.push(uuid);
             }
+            if previous_processing_tasks.contains(task.uid) {
+                task.started_at = Some(previous_started_at);
+            }
             task.status = Status::Canceled;
             task.canceled_by = Some(cancel_task_id);
             task.finished_at = Some(now);

index-scheduler/src/lib.rs

@@ -151,13 +151,12 @@ impl ProcessingTasks {
         self.processing = processing;
     }
 
-    /// Set the processing tasks to an empty list.
-    fn stop_processing_at(&mut self, stopped_at: OffsetDateTime) {
-        self.started_at = stopped_at;
+    /// Set the processing tasks to an empty list
+    fn stop_processing(&mut self) {
         self.processing = RoaringBitmap::new();
     }
 
-    /// Returns `true` if there, at least, is one task that is currently processing we must stop.
+    /// Returns `true` if there, at least, is one task that is currently processing that we must stop.
     fn must_cancel_processing_tasks(&self, canceled_tasks: &RoaringBitmap) -> bool {
         !self.processing.is_disjoint(canceled_tasks)
     }
@@ -449,8 +448,9 @@ impl IndexScheduler {
 
     /// Return the task ids matched by the given query from the index scheduler's point of view.
     pub(crate) fn get_task_ids(&self, rtxn: &RoTxn, query: &Query) -> Result<RoaringBitmap> {
-        let ProcessingTasks { started_at: started_at_processing, processing: processing_tasks } =
-            self.processing_tasks.read().unwrap().clone();
+        let ProcessingTasks {
+            started_at: started_at_processing, processing: processing_tasks, ..
+        } = self.processing_tasks.read().unwrap().clone();
 
         let mut tasks = self.all_task_ids(rtxn)?;
 
@@ -947,6 +947,12 @@ impl IndexScheduler {
                 #[cfg(test)]
                 self.breakpoint(Breakpoint::AbortedIndexation);
                 wtxn.abort().map_err(Error::HeedTransaction)?;
+
+                // We make sure that we don't call `stop_processing` on the `processing_tasks`,
+                // this is because we want to let the next tick call `create_next_batch` and keep
+                // the `started_at` date times and `processings` of the current processing tasks.
+                // This date time is used by the task cancelation to store the right `started_at`
+                // date in the task on disk.
                 return Ok(0);
             }
             // In case of a failure we must get back and patch all the tasks with the error.
@@ -976,7 +982,7 @@ impl IndexScheduler {
             }
         }
 
-        self.processing_tasks.write().unwrap().stop_processing_at(finished_at);
+        self.processing_tasks.write().unwrap().stop_processing();
 
         #[cfg(test)]
         self.maybe_fail(tests::FailureLocation::CommittingWtxn)?;

index-scheduler/src/snapshots/lib.rs/cancel_mix_of_tasks/cancel_processed.snap

@@ -36,6 +36,7 @@ wolfo [2,]
 ----------------------------------------------------------------------
 ### Started At:
 [timestamp] [0,]
+[timestamp] [1,]
 [timestamp] [3,]
 ----------------------------------------------------------------------
 ### Finished At:

index-scheduler/src/snapshots/lib.rs/cancel_processing_task/cancel_processed.snap

@@ -29,6 +29,7 @@ catto [0,]
 [timestamp] [1,]
 ----------------------------------------------------------------------
 ### Started At:
+[timestamp] [0,]
 [timestamp] [1,]
 ----------------------------------------------------------------------
 ### Finished At: