add support for custom log metadata

Author: pietroalbini

src/controllers.rs

@@ -38,6 +38,8 @@ mod prelude {
         fn query(&self) -> IndexMap<String, String>;
         fn wants_json(&self) -> bool;
         fn query_with_params(&self, params: IndexMap<String, String>) -> String;
+
+        fn log_metadata<V: std::fmt::Display>(&mut self, key: &'static str, value: V);
     }
 
     impl<'a> RequestUtils for dyn Request + 'a {
@@ -76,6 +78,10 @@ mod prelude {
                 .finish();
             format!("?{}", query_string)
         }
+
+        fn log_metadata<V: std::fmt::Display>(&mut self, key: &'static str, value: V) {
+            crate::middleware::log_request::add_custom_metadata(self, key, value);
+        }
     }
 }
 

src/middleware.rs

@@ -25,7 +25,7 @@ mod ember_index_rewrite;
 mod ensure_well_formed_500;
 mod head;
 mod log_connection_pool_status;
-mod log_request;
+pub mod log_request;
 mod require_user_agent;
 mod static_or_continue;
 

src/middleware/log_request.rs

@@ -42,6 +42,22 @@ impl Handler for LogRequests {
     }
 }
 
+struct CustomMetadata {
+    entries: Vec<(&'static str, String)>,
+}
+
+pub fn add_custom_metadata<V: Display>(req: &mut dyn Request, key: &'static str, value: V) {
+    if let Some(metadata) = req.mut_extensions().find_mut::<CustomMetadata>() {
+        metadata.entries.push((key, value.to_string()));
+    } else {
+        let mut metadata = CustomMetadata {
+            entries: Vec::new(),
+        };
+        metadata.entries.push((key, value.to_string()));
+        req.mut_extensions().insert(metadata);
+    }
+}
+
 struct RequestLine<'r> {
     req: &'r dyn Request,
     res: &'r Result<Response>,
@@ -66,6 +82,12 @@ impl Display for RequestLine<'_> {
         line.add_field("status", status)?;
         line.add_quoted_field("user_agent", request_header(self.req, "User-Agent"))?;
 
+        if let Some(metadata) = self.req.extensions().find::<CustomMetadata>() {
+            for (key, value) in &metadata.entries {
+                line.add_quoted_field(key, value)?;
+            }
+        }
+
         if let Some(len) = self.req.extensions().find::<u64>() {
             line.add_field("metadata_length", len)?;
         }