Skip unnecessary log formatting, include log category (#261)

This adds the log category to log messages and skips log formatting
altogether when the target log level is not activated.

Author: sgoll

CHANGELOG.md

@@ -7,6 +7,11 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Changed
+
+- Include category ("network", "channel", ..., "discovery") in log messages.
+- Skip overhead of formatting log message when corresponding log level has been disabled.
+
 ## [0.9.3] - 2025-08-27
 
 ### Added

src/ua/logger/rust_log.rs

@@ -1,52 +1,57 @@
 use std::{
+    borrow::Cow,
     ffi::{c_char, c_void, CStr},
     ptr,
 };
 
+use log::Level;
 use open62541_sys::{vsnprintf_va_copy, vsnprintf_va_end, UA_LogCategory, UA_LogLevel, UA_Logger};
 
 use crate::ua;
 
+// This matches the crate name.
 const LOG_TARGET: &str = "open62541_sys";
 
 /// Creates logger that forwards to the `log` crate.
 ///
-/// We can use this to prevent `open62541` from installing its own default logger (which outputs any
+/// We can use this to prevent `open62541` from installing its own default logger (which outputs all
 /// logs to stdout/stderr directly).
 pub(crate) fn logger() -> ua::Logger {
     unsafe extern "C" fn log_c(
         _log_context: *mut c_void,
         level: UA_LogLevel,
-        _category: UA_LogCategory,
+        category: UA_LogCategory,
         msg: *const c_char,
         args: open62541_sys::va_list_,
     ) {
-        let Some(msg) = format_message(msg, args) else {
-            log::error!(target: LOG_TARGET, "Unknown log message");
+        let level = match level {
+            // Without fatal level in `log`, fall back to error.
+            UA_LogLevel::UA_LOGLEVEL_FATAL | UA_LogLevel::UA_LOGLEVEL_ERROR => Level::Error,
+            UA_LogLevel::UA_LOGLEVEL_WARNING => Level::Warn,
+            UA_LogLevel::UA_LOGLEVEL_INFO => Level::Info,
+            UA_LogLevel::UA_LOGLEVEL_DEBUG => Level::Debug,
+            UA_LogLevel::UA_LOGLEVEL_TRACE => Level::Trace,
+            // Handle unexpected level by escalating to error.
+            #[expect(clippy::match_same_arms, reason = "distinction of cases")]
+            _ => Level::Error,
+        };
+
+        if !log::log_enabled!(target: LOG_TARGET, level) {
+            // Bail out early to skip formatting message.
             return;
+        }
+
+        let msg = format_message(msg, args);
+        let msg = match msg {
+            Some(ref msg) => CStr::from_bytes_with_nul(msg)
+                .unwrap_or(c"Invalid log message")
+                .to_string_lossy(),
+            None => Cow::Borrowed("Unknown log message"),
         };
 
-        let msg = CStr::from_bytes_with_nul(&msg)
-            .unwrap_or(c"Invalid log message")
-            .to_string_lossy();
+        let category = log_category(&category);
 
-        if level == UA_LogLevel::UA_LOGLEVEL_FATAL {
-            // Without fatal level in `log`, fall back to error.
-            log::error!(target: LOG_TARGET, "{msg}");
-        } else if level == UA_LogLevel::UA_LOGLEVEL_ERROR {
-            log::error!(target: LOG_TARGET, "{msg}");
-        } else if level == UA_LogLevel::UA_LOGLEVEL_WARNING {
-            log::warn!(target: LOG_TARGET, "{msg}");
-        } else if level == UA_LogLevel::UA_LOGLEVEL_INFO {
-            log::info!(target: LOG_TARGET, "{msg}");
-        } else if level == UA_LogLevel::UA_LOGLEVEL_DEBUG {
-            log::debug!(target: LOG_TARGET, "{msg}");
-        } else if level == UA_LogLevel::UA_LOGLEVEL_TRACE {
-            log::trace!(target: LOG_TARGET, "{msg}");
-        } else {
-            // Handle unexpected level by escalating to error.
-            log::error!(target: LOG_TARGET, "{msg}");
-        }
+        log::log!(target: LOG_TARGET, level, "({category}) {msg}");
     }
 
     unsafe extern "C" fn clear_c(logger: *mut UA_Logger) {
@@ -156,3 +161,32 @@ fn format_message(msg: *const c_char, args: open62541_sys::va_list_) -> Option<V
 
     Some(msg_buffer)
 }
+
+// These match the category names from `ua_log_stdout.c` and `ua_log_syslog.c`.
+const LOG_CATEGORY_NETWORK: &str = "network";
+const LOG_CATEGORY_SECURECHANNEL: &str = "channel";
+const LOG_CATEGORY_SESSION: &str = "session";
+const LOG_CATEGORY_SERVER: &str = "server";
+const LOG_CATEGORY_CLIENT: &str = "client";
+const LOG_CATEGORY_USERLAND: &str = "userland";
+const LOG_CATEGORY_SECURITYPOLICY: &str = "security";
+const LOG_CATEGORY_EVENTLOOP: &str = "eventloop";
+const LOG_CATEGORY_PUBSUB: &str = "pubsub";
+const LOG_CATEGORY_DISCOVERY: &str = "discovery";
+const LOG_CATEGORY_UNKNOWN: &str = "unknown";
+
+const fn log_category(category: &UA_LogCategory) -> &'static str {
+    match *category {
+        UA_LogCategory::UA_LOGCATEGORY_NETWORK => LOG_CATEGORY_NETWORK,
+        UA_LogCategory::UA_LOGCATEGORY_SECURECHANNEL => LOG_CATEGORY_SECURECHANNEL,
+        UA_LogCategory::UA_LOGCATEGORY_SESSION => LOG_CATEGORY_SESSION,
+        UA_LogCategory::UA_LOGCATEGORY_SERVER => LOG_CATEGORY_SERVER,
+        UA_LogCategory::UA_LOGCATEGORY_CLIENT => LOG_CATEGORY_CLIENT,
+        UA_LogCategory::UA_LOGCATEGORY_USERLAND => LOG_CATEGORY_USERLAND,
+        UA_LogCategory::UA_LOGCATEGORY_SECURITYPOLICY => LOG_CATEGORY_SECURITYPOLICY,
+        UA_LogCategory::UA_LOGCATEGORY_EVENTLOOP => LOG_CATEGORY_EVENTLOOP,
+        UA_LogCategory::UA_LOGCATEGORY_PUBSUB => LOG_CATEGORY_PUBSUB,
+        UA_LogCategory::UA_LOGCATEGORY_DISCOVERY => LOG_CATEGORY_DISCOVERY,
+        _ => LOG_CATEGORY_UNKNOWN,
+    }
+}