feat: organize tracing on query path (#3310)

* feat: organize tracing on query path

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

* warp json conversion to TracingContext's methods

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

* remove unnecessary .trace()

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

* Update src/query/src/dist_plan/merge_scan.rs

Co-authored-by: Zhenchi <zhongzc_arch@outlook.com>

---------

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>
Co-authored-by: Zhenchi <zhongzc_arch@outlook.com>

src/common/telemetry/Cargo.toml

@@ -24,6 +24,7 @@ opentelemetry_sdk = { version = "0.21.0", features = ["rt-tokio"] }
 parking_lot = { version = "0.12" }
 prometheus.workspace = true
 serde.workspace = true
+serde_json.workspace = true
 tokio.workspace = true
 tracing = "0.1"
 tracing-appender = "0.2"

src/common/telemetry/src/tracing_context.rs

@@ -89,4 +89,17 @@ impl TracingContext {
         let context = Propagator::new().extract(fields);
         Self(context)
     }
+
+    /// Convert the tracing context to a JSON string in W3C trace context format.
+    pub fn to_json(&self) -> String {
+        serde_json::to_string(&self.to_w3c()).unwrap()
+    }
+
+    /// Create a new tracing context from a JSON string in W3C trace context format.
+    ///
+    /// Illegal json string will produce an empty tracing context and no error will be reported.
+    pub fn from_json(json: &str) -> Self {
+        let fields: W3cTrace = serde_json::from_str(json).unwrap_or_default();
+        Self::from_w3c(&fields)
+    }
 }