format log level

incoming logs as JSON might contain a level which we want to send as a status in datadog logs, applied to AWS JSON logs and also internal logs

Author: duncanista

bottlecap/Cargo.lock

@@ -34,7 +34,7 @@ tokio = { version = "1.47", default-features = false, features = ["macros", "rt-
 tokio-util = { version = "0.7", default-features = false }
 tracing = { version = "0.1", default-features = false }
 tracing-core = { version = "0.1", default-features = false }
-tracing-subscriber = { version = "0.3", default-features = false, features = ["std", "registry", "fmt", "env-filter", "tracing-log"] }
+tracing-subscriber = { version = "0.3", default-features = false, features = ["std", "registry", "fmt", "env-filter", "tracing-log", "json"] }
 hmac = { version = "0.12", default-features = false }
 sha2 = { version = "0.10", default-features = false }
 hex = { version = "0.4", default-features = false, features = ["std"] }

bottlecap/Cargo.toml

@@ -9,6 +9,23 @@ use tracing_subscriber::registry::LookupSpan;
 #[derive(Debug, Clone, Copy)]
 pub struct Formatter;
 
+/// Visitor that captures the message from tracing event fields.
+struct MessageVisitor(String);
+
+impl tracing::field::Visit for MessageVisitor {
+    fn record_debug(&mut self, field: &tracing::field::Field, value: &dyn fmt::Debug) {
+        if field.name() == "message" {
+            self.0 = format!("{value:?}");
+        }
+    }
+
+    fn record_str(&mut self, field: &tracing::field::Field, value: &str) {
+        if field.name() == "message" {
+            self.0 = value.to_string();
+        }
+    }
+}
+
 impl<S, N> FormatEvent<S, N> for Formatter
 where
     S: Subscriber + for<'a> LookupSpan<'a>,
@@ -20,36 +37,38 @@ where
         mut writer: format::Writer<'_>,
         event: &Event<'_>,
     ) -> fmt::Result {
-        // Format values from the event's's metadata:
         let metadata = event.metadata();
-        write!(&mut writer, "DD_EXTENSION | {} | ", metadata.level())?;
+        let level = metadata.level();
+
+        let mut visitor = MessageVisitor(String::new());
+        event.record(&mut visitor);
 
-        // Format all the spans in the event's span context.
+        // Build span context prefix
+        let mut span_prefix = String::new();
         if let Some(scope) = ctx.event_scope() {
             for span in scope.from_root() {
-                write!(writer, "{}", span.name())?;
-
-                // `FormattedFields` is a formatted representation of the span's
-                // fields, which is stored in its extensions by the `fmt` layer's
-                // `new_span` method. The fields will have been formatted
-                // by the same field formatter that's provided to the event
-                // formatter in the `FmtContext`.
+                span_prefix.push_str(span.name());
                 let ext = span.extensions();
                 let fields = &ext
                     .get::<FormattedFields<N>>()
                     .expect("will never be `None`");
-
-                // Skip formatting the fields if the span had no fields.
                 if !fields.is_empty() {
-                    write!(writer, "{{{fields}}}")?;
+                    span_prefix.push('{');
+                    span_prefix.push_str(fields);
+                    span_prefix.push('}');
                 }
-                write!(writer, ": ")?;
+                span_prefix.push_str(": ");
             }
         }
 
-        // Write fields on the event
-        ctx.field_format().format_fields(writer.by_ref(), event)?;
+        let message = format!("DD_EXTENSION | {level} | {span_prefix}{}", visitor.0);
+
+        // Use serde_json for safe serialization (handles escaping automatically)
+        let output = serde_json::json!({
+            "level": level.to_string(),
+            "message": message,
+        });
 
-        writeln!(writer)
+        writeln!(writer, "{output}")
     }
 }