Add additional tracing fields specific to Scylla

docs/source/tracing/tracing.md

@@ -17,7 +17,8 @@ Queries that support tracing:
 * [`Session::prepare()`](prepare.md)
 
 After obtaining the tracing id you can use `Session::get_tracing_info()` to query tracing information.\
-`TracingInfo` contains values that are the same in Scylla and Cassandra®, skipping any database-specific ones.\
+`Session::get_tracing_info()` returns a `TracingInfo` which only contains values that are the same
+in both Scylla and Cassandra®, skipping any database-specific ones.\
 If `TracingInfo` does not contain some needed value it's possible to query it manually from the tables
 `system_traces.sessions` and `system_traces.events`
 

scylla/src/tracing.rs

@@ -18,6 +18,12 @@ pub struct TracingInfo {
     pub request: Option<String>,
     /// started_at is a timestamp - time since unix epoch
     pub started_at: Option<chrono::Duration>,
+    /// only present in Scylla
+    pub request_size: Option<i32>,
+    /// only present in Scylla
+    pub response_size: Option<i32>,
+    /// only present in Scylla
+    pub username: Option<String>,
 
     pub events: Vec<TracingEvent>,
 }
@@ -30,6 +36,10 @@ pub struct TracingEvent {
     pub source: Option<IpAddr>,
     pub source_elapsed: Option<i32>,
     pub thread: Option<String>,
+    /// only present in Scylla
+    pub scylla_parent_id: Option<i64>,
+    /// only present in Scylla
+    pub scylla_span_id: Option<i64>,
 }
 
 impl TracingInfo {
@@ -75,6 +85,9 @@ impl FromRow for TracingInfo {
             parameters,
             request,
             started_at,
+            request_size: None,
+            response_size: None,
+            username: None,
             events: Vec::new(),
         })
     }
@@ -97,6 +110,8 @@ impl FromRow for TracingEvent {
             source,
             source_elapsed,
             thread,
+            scylla_parent_id: None,
+            scylla_span_id: None,
         })
     }
 }

scylla/src/transport/session.rs

@@ -1360,6 +1360,11 @@ impl Session {
     ///
     /// See [the book](https://rust-driver.docs.scylladb.com/stable/tracing/tracing.html)
     /// for more information about query tracing
+    ///
+    /// Does not query for the fields that are only present in the Scylla schema (
+    /// [request_size](TracingInfo::request_size), [response_size](TracingInfo::response_size),
+    /// [username](TracingInfo::username), [scylla_parent_id](TracingEvent::scylla_parent_id),
+    /// and [scylla_span_id](TracingEvent::scylla_span_id)).
     pub async fn get_tracing_info(&self, tracing_id: &Uuid) -> Result<TracingInfo, QueryError> {
         // tracing_info_fetch_attempts is NonZeroU32 so at least one attempt will be made
         for _ in 0..self.tracing_info_fetch_attempts.get() {
@@ -1396,9 +1401,15 @@ impl Session {
         self.keyspace_name.load_full()
     }
 
-    // Tries getting the tracing info
-    // If the queries return 0 rows then returns None - the information didn't reach this node yet
-    // If there is some other error returns this error
+    // Tries getting the tracing info from `system_traces`.
+    //
+    // If the queries return 0 rows then returns `Ok(None)` - the information didn't reach this
+    // node yet.
+    //
+    // If there is some other error returns `Err(that_error)`.
+    //
+    // Does not query for the fields that are only present in the Scylla schema (request_size,
+    // response_size, username, scylla_parent_id, and scylla_span_id).
     async fn try_getting_tracing_info(
         &self,
         tracing_id: &Uuid,