log_json: append the server-notice/log stream to a file as JSONL (log_json = <path>)

src/modules/jsonlog.rs

@@ -63,27 +63,30 @@ fn escape_tag(v: &str) -> String {
     out
 }
 
-/// The escaped `draft/json-log` tag *value* for a server notice `msg`. Place after
-/// `draft/json-log=` in the tag block. echoIRCd snotices are untyped, so `subsystem`
-/// / `event_id` are derived from the leading word and `snomask` is the generic `s`.
-pub fn tag_value(s: &Server, msg: &str) -> String {
+/// The structured JSON object for a server notice `msg` (unescaped). echoIRCd
+/// snotices are untyped, so `subsystem` / `event_id` are derived from the leading
+/// word and `snomask` is the generic `s`. Shared by the tag value and `log_json`.
+pub fn json_line(s: &Server, msg: &str) -> String {
     let head = msg
         .split_whitespace()
         .next()
         .unwrap_or("general")
         .trim_end_matches(':');
-    let subsystem = head.to_ascii_lowercase();
-    let event_id = head.to_ascii_uppercase();
-    let json = obj(&[
+    obj(&[
         ("timestamp", qstr(&iso_time(now()))),
         ("level", qstr("info")),
-        ("subsystem", qstr(&subsystem)),
-        ("event_id", qstr(&event_id)),
+        ("subsystem", qstr(&head.to_ascii_lowercase())),
+        ("event_id", qstr(&head.to_ascii_uppercase())),
         ("log_source", qstr(&s.name)),
         ("msg", qstr(&strip_formatting(msg))),
         ("snomask", qstr("s")),
-    ]);
-    escape_tag(&json)
+    ])
+}
+
+/// The escaped `draft/json-log` tag *value* for a server notice `msg`. Place after
+/// `draft/json-log=` in the tag block.
+pub fn tag_value(s: &Server, msg: &str) -> String {
+    escape_tag(&json_line(s, msg))
 }
 
 #[cfg(test)]

src/modules/log_json.rs

@@ -0,0 +1,46 @@
+//! log_json — append the server-notice / log stream to a file as JSON, one object
+//! per line (JSONL). Off unless `log_json = <path>` is set. Reuses the
+//! `draft/json-log` object builder. The file handle is cached on the core thread
+//! (snotice is single-threaded) and reopened if the path changes or a write fails —
+//! so an external logrotate that renames the file is picked up on the next line.
+
+use std::cell::RefCell;
+use std::fs::{File, OpenOptions};
+use std::io::Write;
+
+use crate::server::Server;
+
+thread_local! {
+    /// (configured path, open append handle) cached for reuse.
+    static SINK: RefCell<Option<(String, File)>> = const { RefCell::new(None) };
+}
+
+/// Append `msg` as a JSON line to the configured log file. Called at the tail of
+/// [`Server::snotice`].
+pub fn tee(s: &Server, msg: &str) {
+    let Some(path) = s.conf("log_json") else {
+        SINK.with(|c| *c.borrow_mut() = None); // disabled: drop any handle
+        return;
+    };
+    let line = crate::modules::jsonlog::json_line(s, msg);
+    SINK.with(|cell| {
+        let mut slot = cell.borrow_mut();
+        let need_open = match slot.as_ref() {
+            Some((p, _)) => p != path,
+            None => true,
+        };
+        if need_open {
+            *slot = OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(path)
+                .ok()
+                .map(|f| (path.to_string(), f));
+        }
+        if let Some((_, f)) = slot.as_mut() {
+            if writeln!(f, "{line}").is_err() {
+                *slot = None; // reopen next time
+            }
+        }
+    });
+}

src/modules/mod.rs

@@ -41,6 +41,7 @@ pub mod ident;
 pub mod irccloudtags;
 pub mod jsonlog;
 pub mod jwt;
+pub mod log_json;
 pub mod maphide;
 pub mod markread;
 pub mod metadata;