metrics: Implement iocaine_maze_depth

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 ### Added
 
 - The `iocaine_garbage_served` metric will have the same labels applied to it as `iocaine_requests_total`.
+- Implemented a new metric, `iocaine_maze_depth`, a counter to track how deep the maze has been explored so far.
 - When metrics are enabled, process metrics such as CPU seconds used, memory usage, etc, are also emitted.
 
 ## [1.0.0] - 2025-03-01

src/app.rs

@@ -123,7 +123,7 @@ async fn poison(
 ) -> std::result::Result<Html<String>, AppError> {
     let default_host = axum::http::HeaderValue::from_static("<unknown>");
     let host = headers.get("host").unwrap_or(&default_host).to_str()?;
-    let path = path.unwrap_or(Path("/".to_string()));
+    let path = path.unwrap_or(Path("".to_string()));
 
     let garbage = AssembledStatisticalSequences::generate(&state.iocaine, host, &path)?;
 
@@ -135,6 +135,13 @@ async fn poison(
             .garbage_served_counter
             .with_label_values(&labels)
             .inc_by(garbage.len() as u64);
+
+        let depth = path.chars().filter(|c| *c == '/').count() as u64;
+        let maze_depth_counter = counters.maze_depth.with_label_values(&labels);
+        let maze_depth = maze_depth_counter.get();
+        if depth > maze_depth {
+            maze_depth_counter.inc_by(depth - maze_depth);
+        }
     }
 
     Ok(Html(garbage))

src/tenx_programmer.rs

@@ -22,6 +22,7 @@ pub struct TenXProgrammer {
 pub struct TenXProgrammerCounters {
     pub request_counter: IntCounterVec,
     pub garbage_served_counter: IntCounterVec,
+    pub maze_depth: IntCounterVec,
 }
 
 impl TenXProgrammer {
@@ -109,11 +110,19 @@ impl TenXProgrammer {
             .register(Box::new(garbage_served_counter.clone()))
             .unwrap();
 
+        let maze_depth_opts = Opts::new(
+            "iocaine_maze_depth",
+            "Maximum explored depth of the maze (in path parts)",
+        );
+        let maze_depth = IntCounterVec::new(maze_depth_opts, &labels).unwrap();
+        registry.register(Box::new(maze_depth.clone())).unwrap();
+
         Some(Self {
             registry,
             counters: TenXProgrammerCounters {
                 request_counter,
                 garbage_served_counter,
+                maze_depth,
             },
         })
     }