[WIP] Display descriptive error message when socket path too long

gravity/process_manager/supervisor_manager.py

@@ -3,6 +3,7 @@
 import errno
 import os
 import shutil
+import socket
 import subprocess
 import sys
 import time
@@ -194,6 +195,8 @@ def __init__(self, state_dir=None, start_daemon=True, foreground=False):
         self.__supervisord_popen = None
         self.foreground = foreground
 
+        self._check_path_length()
+
         if not exists(self.supervisord_conf_dir):
             os.makedirs(self.supervisord_conf_dir)
 
@@ -225,7 +228,8 @@ def __supervisord(self):
         if not self.__supervisord_is_running():
             # any time that supervisord is not running, let's rewrite supervisord.conf
             open(self.supervisord_conf_path, "w").write(SUPERVISORD_CONF_TEMPLATE.format(**format_vars))
-            self.__supervisord_popen = subprocess.Popen(supervisord_cmd, env=os.environ)
+            self.__supervisord_popen = subprocess.Popen(supervisord_cmd, env=os.environ, stderr=subprocess.PIPE)
+
             rc = self.__supervisord_popen.poll()
             if rc:
                 error("supervisord exited with code %d" % rc)
@@ -243,6 +247,29 @@ def __get_supervisor(self):
         options.realize(args=["-c", self.supervisord_conf_path])
         return supervisorctl.Controller(options).get_supervisor()
 
+    def _check_path_length(self):
+        sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        bind_path = self.supervisord_conf_path
+        try:
+            sock.bind(bind_path)
+        except OSError as e:
+            if "AF_UNIX path too long" in str(e):
+                self._handle_socket_path_error()
+        finally:
+            sock.close()
+            os.unlink(bind_path)
+
+    def _handle_socket_path_error(self):
+        msg = f"""
+        The path to your gravity state directory is too long: "{self.supervisord_conf_dir}".
+        This path becomes part of a socket address. However, in Unix systems there is a limit to the
+        length of a socket file path (usually 103-108 bytes). You can choose another path with the
+        --state-dir option to the Gravity command, or by setting $GRAVITY_STATE_DIR in your
+        environment:
+        `galaxy --state-dir /home/shorter-path` or `$GRAVITY_STATE_DIR=/home/shorter-path ./run.sh`
+        """
+        error(msg)
+
     def terminate(self):
         if self.foreground:
             # if running in foreground, if terminate is called, then supervisord should've already received a SIGINT