Move logging initialization into Fastly adapter (PR 10)

crates/trusted-server-adapter-fastly/src/logging.rs

@@ -0,0 +1,77 @@
+use chrono::{SecondsFormat, Utc};
+use log_fastly::Logger;
+
+/// Extracts the final `::` segment from a Rust module path for use as a log label.
+///
+/// Falls back to the full target string when the input contains no separator or
+/// when the separator appears at the trailing position (e.g. `"foo::"`), which
+/// would otherwise produce an empty label in log output.
+fn target_label(target: &str) -> &str {
+    match target.rsplit_once("::") {
+        Some((head, "")) => head,
+        Some((_, last)) => last,
+        None => target,
+    }
+}
+
+/// Initialises the Fastly-backed `fern` logger and installs it as the global logger.
+///
+/// Log records are forwarded to the `tslog` Fastly endpoint and echoed to stdout.
+/// Each line is prefixed with an RFC 3339 timestamp, level, and the final segment
+/// of the record's target module path.
+///
+/// # Panics
+///
+/// Panics if the logger cannot be built or if a global logger has already been set.
+pub(crate) fn init_logger() {
+    let logger = Logger::builder()
+        .default_endpoint("tslog")
+        .echo_stdout(true)
+        .max_level(log::LevelFilter::Info)
+        .build()
+        .expect("should build Logger");
+
+    fern::Dispatch::new()
+        .format(|out, message, record| {
+            out.finish(format_args!(
+                "{} {} [{}] {}",
+                Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true),
+                record.level(),
+                target_label(record.target()),
+                message
+            ));
+        })
+        .chain(Box::new(logger) as Box<dyn log::Log>)
+        .apply()
+        .expect("should initialize logger");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn target_label_extracts_correct_segment() {
+        assert_eq!(
+            target_label("trusted_server_adapter_fastly::proxy"),
+            "proxy",
+            "should handle standard single-separator case"
+        );
+        assert_eq!(
+            target_label("foo::bar::baz"),
+            "baz",
+            "should handle multiple separators"
+        );
+        assert_eq!(
+            target_label("no_separators_here"),
+            "no_separators_here",
+            "should handle inputs without ::"
+        );
+        assert_eq!(target_label(""), "", "should handle empty strings");
+        assert_eq!(
+            target_label("trailing::"),
+            "trailing",
+            "should strip separator when trailing segment is empty"
+        );
+    }
+}

crates/trusted-server-adapter-fastly/src/main.rs

@@ -1,7 +1,6 @@
 use error_stack::Report;
 use fastly::http::Method;
 use fastly::{Error, Request, Response};
-use log_fastly::Logger;
 
 use trusted_server_core::auction::endpoints::handle_auction;
 use trusted_server_core::auction::{build_orchestrator, AuctionOrchestrator};
@@ -28,6 +27,7 @@ use trusted_server_core::settings::Settings;
 use trusted_server_core::settings_data::get_settings;
 
 mod error;
+mod logging;
 mod management_api;
 mod platform;
 
@@ -36,7 +36,7 @@ use crate::platform::{build_runtime_services, open_kv_store, UnavailableKvStore}
 
 #[fastly::main]
 fn main(req: Request) -> Result<Response, Error> {
-    init_logger();
+    logging::init_logger();
 
     // Keep the health probe independent from settings loading and routing so
     // readiness checks still get a cheap liveness response during startup.
@@ -241,30 +241,3 @@ fn finalize_response(settings: &Settings, geo_info: Option<&GeoInfo>, response:
         response.set_header(key, value);
     }
 }
-
-fn init_logger() {
-    let logger = Logger::builder()
-        .default_endpoint("tslog")
-        .echo_stdout(true)
-        .max_level(log::LevelFilter::Info)
-        .build()
-        .expect("should build Logger");
-
-    fern::Dispatch::new()
-        .format(|out, message, record| {
-            out.finish(format_args!(
-                "{} {} [{}] {}",
-                chrono::Local::now().to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
-                record.level(),
-                record
-                    .target()
-                    .split("::")
-                    .last()
-                    .unwrap_or(record.target()),
-                message
-            ))
-        })
-        .chain(Box::new(logger) as Box<dyn log::Log>)
-        .apply()
-        .expect("should initialize logger");
-}

crates/trusted-server-core/Cargo.toml

@@ -33,7 +33,6 @@ iab_gpp = { workspace = true }
 jose-jwk = { workspace = true }
 log = { workspace = true }
 rand = { workspace = true }
-log-fastly = { workspace = true }
 lol_html = { workspace = true }
 matchit = { workspace = true }
 pin-project-lite = { workspace = true }