Start panda server and extension server in procServ if available

That simplifies checking investigation when there are problems.
Additionally, extension server pid file support was added so that it
can be killed when running without procServ.

This fixes #50.

etc/panda-server

@@ -5,7 +5,8 @@
 . /etc/init.d/functions
 
 # File locations
-pidfile=/var/run/panda-server.pid
+server_pid_file=/var/run/panda-server.pid
+extension_pid_file=/var/run/panda-extensions.pid
 
 panda_server=/opt/bin/panda_server
 panda_config=/opt/share/panda-fpga/config_d
@@ -58,19 +59,38 @@ do_start()
         i=$((i+1))
     done  &&
 
-    # Now start the extension server
-    $extension_server -d -s $extension_dir  &&
-
-    # Finally start the PANDA server
-    $panda_server \
-        -c $panda_config -f $panda_state -P $pidfile -D -R -X 9999 \
-        -r "$(head -n1 /etc/version)" \
-        $panda_server_mac
+    # Now start the extension server (in procServ if available)
+    {
+        if type procServ &> /dev/null; then
+            procServ -n panda-extensions -p $extension_pid_file \
+                -L /var/log/panda-extensions-console 8021 \
+                $extension_server -s $extension_dir
+        else
+            $extension_server -d -s $extension_dir -P $extension_pid_file
+        fi
+    } &&
+    {
+        # Finally start the PANDA server (in procServ if available)
+        if type procServ &> /dev/null; then
+            procServ -n panda-server -p $server_pid_file \
+                -L /var/log/panda-server-console 8022 \
+                $panda_server \
+                    -c $panda_config -f $panda_state -R -X 9999 \
+                    -r "$(head -n1 /etc/version)" \
+                    $panda_server_mac
+        else
+            $panda_server \
+                -c $panda_config -f $panda_state -P $server_pid_file -D -R \
+                -X 9999 -r "$(head -n1 /etc/version)" \
+                $panda_server_mac
+        fi
+    }
 }
 
 do_stop()
 {
-    kill -HUP $(cat $pidfile)  &&
+    kill $(cat $server_pid_file)  &&
+    kill $(cat $extension_pid_file) &&
 
     # Remove the Panda driver.  We have to keep trying because we can't actually
     # unload it until the server has finished shutting down.

python/extension_server

@@ -3,6 +3,7 @@
 # Extension server for custom fields implemented outside the core server
 
 import argparse
+import atexit
 import os
 import sys
 from importlib import import_module
@@ -254,6 +255,7 @@ parser.add_argument(
 parser.add_argument(
     '-n', '--normalise_exceptions', action = 'store_true',
     help = 'Normalise exception messages reported by server.  Testing only')
+parser.add_argument('-P', '--pidfile', help = 'Save PID to file specified')
 parser.add_argument(
     'extensions', help = 'Extension directory')
 command_args = parser.parse_args()
@@ -293,6 +295,12 @@ logging.info('Extension server ready')
 if command_args.daemon:
     daemonise()
 
+if command_args.pidfile:
+    with open(command_args.pidfile, 'w') as fhandle:
+        fhandle.write(f'{os.getpid()}')
+
+    atexit.register(lambda: os.unlink(command_args.pidfile))
+
 try:
     server.run()
 except KeyboardInterrupt: