chore: log and flush

src/mito2/src/worker.rs

@@ -126,6 +126,11 @@ impl WorkerGroup {
             })
             .collect();
 
+        info!(
+            "Started region worker group with {} workers",
+            config.num_workers
+        );
+
         WorkerGroup { workers, scheduler }
     }
 

src/mito2/src/worker/handle_flush.rs

@@ -165,6 +165,10 @@ impl<S> RegionWorkerLoop<S> {
         // Flush memtable with max mutable memtable.
         // TODO(yingwen): Maybe flush more tables to reduce write buffer size.
         if let Some(region) = max_mem_region {
+            info!(
+                "Chosen the region {} with the maximum mutable memtable size to flush: {}.",
+                region.region_id, max_mutable_size
+            );
             if !self.flush_scheduler.is_flush_requested(region.region_id) {
                 let task = self.new_flush_task(region, FlushReason::EngineFull);
                 self.flush_scheduler.schedule_flush(region, task)?;

src/mito2/src/worker/handle_write.rs

@@ -35,13 +35,13 @@ impl<S: LogStore> RegionWorkerLoop<S> {
         mut write_requests: Vec<SenderWriteRequest>,
         allow_stall: bool,
     ) {
+        // Flush this worker if the engine needs to flush.
+        self.maybe_flush_worker();
+
         if write_requests.is_empty() {
             return;
         }
 
-        // Flush this worker if the engine needs to flush.
-        self.maybe_flush_worker();
-
         if self.should_reject_write() {
             // The memory pressure is still too high, reject write requests.
             reject_write_requests(write_requests);