refactor: bring metrics to http output (#3247)

* refactor: bring metrics to http output

* chore: remove unwrap

* chore: make walk plan accumulate

* chore: change field name and comment

* chore: add metrics to http resp header

* chore: move PrometheusJsonResponse to a separate file and impl IntoResponse

* chore: put metrics in prometheus resp header too

src/common/recordbatch/src/adapter.rs

@@ -182,7 +182,7 @@ pub struct RecordBatchStreamAdapter {
 enum Metrics {
     Unavailable,
     Unresolved(Arc<dyn ExecutionPlan>),
-    Resolved(String),
+    Resolved(RecordBatchMetrics),
 }
 
 impl RecordBatchStreamAdapter {
@@ -222,9 +222,9 @@ impl RecordBatchStream for RecordBatchStreamAdapter {
         self.schema.clone()
     }
 
-    fn metrics(&self) -> Option<String> {
+    fn metrics(&self) -> Option<RecordBatchMetrics> {
         match &self.metrics_2 {
-            Metrics::Resolved(metrics) => Some(metrics.clone()),
+            Metrics::Resolved(metrics) => Some(*metrics),
             Metrics::Unavailable | Metrics::Unresolved(_) => None,
         }
     }
@@ -254,8 +254,7 @@ impl Stream for RecordBatchStreamAdapter {
                     let mut metrics_holder = RecordBatchMetrics::default();
                     collect_metrics(df_plan, &mut metrics_holder);
                     if metrics_holder.elapsed_compute != 0 || metrics_holder.memory_usage != 0 {
-                        self.metrics_2 =
-                            Metrics::Resolved(serde_json::to_string(&metrics_holder).unwrap());
+                        self.metrics_2 = Metrics::Resolved(metrics_holder);
                     }
                 }
                 Poll::Ready(None)
@@ -285,7 +284,7 @@ fn collect_metrics(df_plan: &Arc<dyn ExecutionPlan>, result: &mut RecordBatchMet
 
 /// [`RecordBatchMetrics`] carrys metrics value
 /// from datanode to frontend through gRPC
-#[derive(serde::Serialize, serde::Deserialize, Default, Debug)]
+#[derive(serde::Serialize, serde::Deserialize, Default, Debug, Clone, Copy)]
 pub struct RecordBatchMetrics {
     // cpu consumption in nanoseconds
     pub elapsed_compute: usize,

src/common/recordbatch/src/lib.rs

@@ -21,6 +21,7 @@ pub mod util;
 use std::pin::Pin;
 use std::sync::Arc;
 
+use adapter::RecordBatchMetrics;
 use arc_swap::ArcSwapOption;
 use datafusion::physical_plan::memory::MemoryStream;
 pub use datafusion::physical_plan::SendableRecordBatchStream as DfSendableRecordBatchStream;
@@ -42,7 +43,7 @@ pub trait RecordBatchStream: Stream<Item = Result<RecordBatch>> {
         None
     }
 
-    fn metrics(&self) -> Option<String> {
+    fn metrics(&self) -> Option<RecordBatchMetrics> {
         None
     }
 }
@@ -212,7 +213,7 @@ pub struct RecordBatchStreamWrapper<S> {
     pub schema: SchemaRef,
     pub stream: S,
     pub output_ordering: Option<Vec<OrderOption>>,
-    pub metrics: Arc<ArcSwapOption<String>>,
+    pub metrics: Arc<ArcSwapOption<RecordBatchMetrics>>,
 }
 
 impl<S> RecordBatchStreamWrapper<S> {
@@ -238,8 +239,8 @@ impl<S: Stream<Item = Result<RecordBatch>> + Unpin> RecordBatchStream
         self.output_ordering.as_deref()
     }
 
-    fn metrics(&self) -> Option<String> {
-        self.metrics.load().as_ref().map(|s| s.as_ref().clone())
+    fn metrics(&self) -> Option<RecordBatchMetrics> {
+        self.metrics.load().as_ref().map(|s| *s.as_ref())
     }
 }