Check for agent already running (#16937)

* Check for server socket listen setup and exit normally instead of fatal()
Move ML initialization until after socket listen is successful

* Switch to error level

(cherry picked from commit 8920bcbfc18cdeec4b8fd91c3756032e00ccc32b)

3 files changed, 21 insertions, 11 deletions

diff --git a/daemon/main.c b/daemon/main.c
index a74e1e1984..3e1fda963b 100644
--- a/daemon/main.c
+++ b/daemon/main.c
@@ -2008,11 +2008,11 @@ int main(int argc, char **argv) {
         set_silencers_filename();
         health_initialize_global_silencers();
 
-        // --------------------------------------------------------------------
-        // Initialize ML configuration
-
-        delta_startup_time("initialize ML");
-        ml_init();
+//        // --------------------------------------------------------------------
+//        // Initialize ML configuration
+//
+//        delta_startup_time("initialize ML");
+//        ml_init();
 
         // --------------------------------------------------------------------
         // setup process signals
@@ -2065,8 +2065,18 @@ int main(int argc, char **argv) {
         web_client_api_v1_init();
         web_server_threading_selection();
 
-        if(web_server_mode != WEB_SERVER_MODE_NONE)
-            api_listen_sockets_setup();
+        if(web_server_mode != WEB_SERVER_MODE_NONE) {
+            if (!api_listen_sockets_setup()) {
+                netdata_log_error("Cannot setup listen port(s). Is Netdata already running?");
+                exit(1);
+            }
+        }
+
+        // --------------------------------------------------------------------
+        // Initialize ML configuration
+
+        delta_startup_time("initialize ML");
+        ml_init();
 
 #ifdef ENABLE_H2O
         delta_startup_time("initialize h2o server");
diff --git a/web/server/web_server.c b/web/server/web_server.c
index 8ac0c6595f..86c5dccf03 100644
--- a/web/server/web_server.c
+++ b/web/server/web_server.c
@@ -57,16 +57,16 @@ void debug_sockets() {
 	buffer_free(wb);
 }
 
-void api_listen_sockets_setup(void) {
+bool api_listen_sockets_setup(void) {
 	int socks = listen_sockets_setup(&api_sockets);
 
 	if(!socks)
-		fatal("LISTENER: Cannot listen on any API socket. Exiting...");
+        return false;
 
 	if(unlikely(debug_flags & D_WEB_CLIENT))
 		debug_sockets();
 
-	return;
+	return true;
 }
 
 
diff --git a/web/server/web_server.h b/web/server/web_server.h
index 3b88d1a22c..a31938c8d9 100644
--- a/web/server/web_server.h
+++ b/web/server/web_server.h
@@ -39,7 +39,7 @@ extern WEB_SERVER_MODE web_server_mode;
 WEB_SERVER_MODE web_server_mode_id(const char *mode);
 const char *web_server_mode_name(WEB_SERVER_MODE id);
 
-void api_listen_sockets_setup(void);
+bool api_listen_sockets_setup(void);
 
 #define DEFAULT_TIMEOUT_TO_RECEIVE_FIRST_WEB_REQUEST 60
 #define DEFAULT_DISCONNECT_IDLE_WEB_CLIENTS_AFTER_SECONDS 60