fix: log worker crashes at warn level instead of debug

A worker script that dies after boot (non-zero exit status) currently logs
the same debug-level "restarting" message as a clean FRANKENPHP_LOOP_MAX
recycle. At the default log level a crash is therefore invisible: the
in-flight request surfaces as an empty 500, the application never gets to
log anything (the script died mid-request), and the exit status - the one
datum needed to triage the death - is only available by running the whole
server at debug level.

Up to v1.2.x these terminations were logged at error level with the
distinct message "unexpected termination, restarting" (see e.g. #774,
where that log line is how the reporter noticed the problem at all). This
restores that message at warn level, matching the other worker-failure
logs in tearDownWorkerScript, and keeps clean restarts at debug.

Also aligns the guard of the watcher-enabled boot-failure log with the
level it actually logs at (Enabled checked Error, LogAttrs wrote Warn).

Author: luminalpark

testdata/crashing-worker.php

@@ -0,0 +1,15 @@
+<?php
+
+// Boots successfully, then terminates with a non-zero exit status while
+// handling its second request, simulating a worker crash after boot.
+$requests = 0;
+$handler = static function () use (&$requests) {
+    if (++$requests >= 2) {
+        exit(1);
+    }
+
+    echo 'ok';
+};
+
+while (frankenphp_handle_request($handler)) {
+}

threadworker.go

@@ -160,8 +160,10 @@ func tearDownWorkerScript(handler *workerThread, exitStatus int) {
 
 	if !handler.isBootingScript {
 		// fatal error (could be due to exit(1), timeouts, etc.)
-		if globalLogger.Enabled(globalCtx, slog.LevelDebug) {
-			globalLogger.LogAttrs(globalCtx, slog.LevelDebug, "restarting", slog.String("worker", worker.name), slog.Int("thread", handler.thread.threadIndex), slog.Int("exit_status", exitStatus))
+		// unlike a clean restart, this took down any in-flight request, so
+		// surface it above debug level, with the exit status needed to triage it
+		if globalLogger.Enabled(globalCtx, slog.LevelWarn) {
+			globalLogger.LogAttrs(globalCtx, slog.LevelWarn, "unexpected termination, restarting", slog.String("worker", worker.name), slog.Int("thread", handler.thread.threadIndex), slog.Int("exit_status", exitStatus))
 		}
 
 		return
@@ -175,7 +177,7 @@ func tearDownWorkerScript(handler *workerThread, exitStatus int) {
 
 	if watcherIsEnabled {
 		// worker script has probably failed due to script changes while watcher is enabled
-		if globalLogger.Enabled(globalCtx, slog.LevelError) {
+		if globalLogger.Enabled(globalCtx, slog.LevelWarn) {
 			globalLogger.LogAttrs(globalCtx, slog.LevelWarn, "(watcher enabled) worker script has not reached frankenphp_handle_request()", slog.String("worker", worker.name), slog.Int("thread", handler.thread.threadIndex))
 		}
 	} else {

worker_test.go

@@ -112,6 +112,18 @@ func TestWorkerGetOpt(t *testing.T) {
 	assert.NotRegexp(t, buf.String(), "exit_status=[1-9]")
 }
 
+func TestWorkerCrashIsLoggedAboveDebugLevel(t *testing.T) {
+	logger, buf := newTestLogger(t)
+
+	runTest(t, func(handler func(http.ResponseWriter, *http.Request), _ *httptest.Server, i int) {
+		req := httptest.NewRequest("GET", "http://example.com/crashing-worker.php", nil)
+		w := httptest.NewRecorder()
+		handler(w, req)
+	}, &testOptions{logger: logger, workerScript: "crashing-worker.php", nbWorkers: 1, nbParallelRequests: 4})
+
+	assert.Regexp(t, `level=WARN msg="unexpected termination, restarting" worker=\S+ thread=\d+ exit_status=1`, buf.String())
+}
+
 func ExampleServeHTTP_workers() {
 	if err := frankenphp.Init(
 		frankenphp.WithWorkers("worker1", "worker1.php", 4,