nghttpx: Redirect stderr to errorlog file

src/shrpx.cc

@@ -422,6 +422,7 @@ void reopen_log_signal_cb(struct ev_loop *loop, ev_signal *w, int revents) {
   }
 
   (void)reopen_log_files();
+  redirect_stderr_to_errorlog();
 
   if (get_config()->num_worker > 1) {
     conn_handler->worker_reopen_log_files();
@@ -636,6 +637,10 @@ int event_loop() {
 
     // We get new PID after successful daemon().
     mod_config()->pid = getpid();
+
+    // daemon redirects stderr file descriptor to /dev/null, so we
+    // need this.
+    redirect_stderr_to_errorlog();
   }
 
   if (get_config()->pid_file) {
@@ -1916,6 +1921,8 @@ int main(int argc, char **argv) {
     exit(EXIT_FAILURE);
   }
 
+  redirect_stderr_to_errorlog();
+
   if (get_config()->uid != 0) {
     if (log_config()->accesslog_fd != -1 &&
         fchown(log_config()->accesslog_fd, get_config()->uid,

src/shrpx_log.cc

@@ -324,4 +324,14 @@ int reopen_log_files() {
   return res;
 }
 
+void redirect_stderr_to_errorlog() {
+  auto lgconf = log_config();
+
+  if (get_config()->errorlog_syslog || lgconf->errorlog_fd == -1) {
+    return;
+  }
+
+  dup2(lgconf->errorlog_fd, STDERR_FILENO);
+}
+
 } // namespace shrpx

src/shrpx_log.h

@@ -143,6 +143,8 @@ void upstream_accesslog(const std::vector<LogFragment> &lf, LogSpec *lgsp);
 
 int reopen_log_files();
 
+void redirect_stderr_to_errorlog();
+
 } // namespace shrpx
 
 #endif // SHRPX_LOG_H