Remove unwrap() in sonic-host-services (#331)

unwrap() function may crash in runtime.
1. For constant value which is safe, we use expect() instead of unwrap(), so any future programming mistake on changing the constant value could get better crash message. Current value will not trigger crash.
2. For float may be NaN, handle it safely
3. Handle initialization errors gracefully

Author: mssonicbld

crates/procdockerstatsd-rs/src/main.rs

@@ -70,7 +70,7 @@ fn get_terminal_name(pid: u32) -> String {
 }
 
 fn convert_to_bytes(value: &str) -> u64 {
-    static RE: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"(\d+\.?\d*)([a-zA-Z]+)").unwrap());
+    static RE: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"(\d+\.?\d*)([a-zA-Z]+)").expect("valid regex pattern"));
     if let Some(caps) = RE.captures(value) {
         let num: f64 = caps[1].parse().unwrap_or(0.0);
         let unit = &caps[2];
@@ -191,14 +191,17 @@ impl ProcDockerStats {
                 ProcessStatus::Unknown(_) | ProcessStatus::Zombie => continue,
                 _ => {
                     let cpu = process_obj.cpu_usage();
-                    valid_processes.push((cpu, process_obj));
+                    // Treat NaN as 0.0 for sorting purposes
+                    let cpu_safe = if cpu.is_nan() { 0.0 } else { cpu };
+                    valid_processes.push((cpu_safe, process_obj));
                 }
             }
         }
         // Partial sort: only need top 1024, so use select_nth_unstable for O(n) instead of O(n log n)
         let limit = 1024.min(valid_processes.len());
         if limit > 0 {
-            valid_processes.select_nth_unstable_by(limit - 1, |a, b| b.0.partial_cmp(&a.0).unwrap());
+            // Safe to use total_cmp now since we've already handled NaN above
+            valid_processes.select_nth_unstable_by(limit - 1, |a, b| b.0.total_cmp(&a.0));
         }
         let top_processes = valid_processes.iter().take(limit).map(|(_, p)| *p);
 
@@ -353,14 +356,15 @@ impl ProcDockerStats {
     }
 }
 
-fn main() {
+fn main() -> Result<(), Box<dyn std::error::Error>> {
     // Initialize tracing with syslog like sonic-ctrmgrd-rs example
-    let identity = CString::new("procdockerstatsd").unwrap();
+    let identity = CString::new("procdockerstatsd")
+        .map_err(|e| format!("invalid identity string: {}", e))?;
     let syslog = syslog_tracing::Syslog::new(
         identity,
         syslog_tracing::Options::LOG_PID,
         syslog_tracing::Facility::Daemon
-    ).unwrap();
+    ).ok_or("failed to initialize syslog")?;
     tracing_subscriber::fmt()
         .with_writer(syslog)
         .with_ansi(false)
@@ -371,6 +375,7 @@ fn main() {
 
     info!("Starting up procdockerstatsd daemon");
 
-    let mut daemon = ProcDockerStats::new().expect("Failed to initialize daemon");
+    let mut daemon = ProcDockerStats::new()?;
     daemon.run();
+    Ok(())
 }