address more comments

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

CHANGELOG.md

@@ -6,11 +6,14 @@
 
 * Unconditionally tolerate `fallocate` failures as a fix to its portability issue. Errors other than `EOPNOTSUPP` will still emit a warning.
 
+### New Features
+
+* Add `PerfContext` which records detailed time breakdown of the write process to thread-local storage.
+
 ### Public API Changes
 
 * Add `is_empty` to `Engine` API.
 * Add metadata deletion capability to `FileSystem` trait. Users can implement `exists_metadata` and `delete_metadata` to clean up obsolete metadata from older versions of Raft Engine.
-* Add `PerfContext` which records detailed time breakdown of the write process to thread-local storage.
 
 ## [0.2.0] - 2022-05-25
 

src/engine.rs

@@ -182,8 +182,9 @@ where
             let entered_time = writer.entered_time.unwrap();
             ENGINE_WRITE_PREPROCESS_DURATION_HISTOGRAM
                 .observe(entered_time.saturating_duration_since(start).as_secs_f64());
-            perf_context.write_leader_wait_duration +=
+            perf_context.write_wait_duration +=
                 entered_time.saturating_duration_since(before_enter);
+            debug_assert_eq!(writer.perf_context_diff.write_wait_duration, Duration::ZERO);
             perf_context += &writer.perf_context_diff;
             set_perf_context(perf_context);
             writer.finish()?

src/metrics.rs

@@ -46,8 +46,8 @@ pub struct PerfContext {
     /// Time spent encoding and compressing log entries.
     pub log_populating_duration: Duration,
 
-    /// Time spent waiting for becoming the write leader.
-    pub write_leader_wait_duration: Duration,
+    /// Time spent waiting for the write group to form and get processed.
+    pub write_wait_duration: Duration,
 
     /// Time spent writing the logs to files.
     pub log_write_duration: Duration,
@@ -65,7 +65,7 @@ pub struct PerfContext {
 impl AddAssign<&'_ PerfContext> for PerfContext {
     fn add_assign(&mut self, rhs: &PerfContext) {
         self.log_populating_duration += rhs.log_populating_duration;
-        self.write_leader_wait_duration += rhs.write_leader_wait_duration;
+        self.write_wait_duration += rhs.write_wait_duration;
         self.log_write_duration += rhs.log_write_duration;
         self.log_rotate_duration += rhs.log_rotate_duration;
         self.log_sync_duration += rhs.log_sync_duration;