systemd: $MAINPID handover for NotifyAccess=main

Author: pajod

docs/source/settings.rst

@@ -1595,6 +1595,11 @@ If the ``PORT`` environment variable is defined, the default
 is ``['0.0.0.0:$PORT']``. If it is not defined, the default
 is ``['127.0.0.1:8000']``.
 
+.. note::
+   Specifying any fd://FD socket or inheriting any socket from systemd
+   (LISTEN_FDS) results in other bind addresses to be skipped.
+   Do not mix fd://FD and systemd socket activation.
+
 .. _backlog:
 
 ``backlog``

gunicorn/arbiter.py

@@ -151,6 +151,7 @@ def start(self):
                 self.systemd = True
                 fds = range(systemd.SD_LISTEN_FDS_START,
                             systemd.SD_LISTEN_FDS_START + listen_fds)
+                self.log.debug("Inherited sockets from systemd: %r", fds)
 
             elif self.master_pid:
                 fds = []
@@ -350,7 +351,12 @@ def wakeup(self):
 
     def halt(self, reason=None, exit_status=0):
         """ halt arbiter """
-        systemd.sd_notify("STOPPING=1\nSTATUS=Gunicorn shutting down..", self.log)
+        if self.master_pid != 0:
+            # if NotifyAccess=main, systemd needs to know old master is in control
+            systemd.sd_notify("READY=1\nMAINPID=%d\nSTATUS=New arbiter shutdown" % (self.master_pid, ), self.log)
+        elif self.reexec_pid == 0:
+            # skip setting status if this is merely superseded master stopping
+            systemd.sd_notify("STOPPING=1\nSTATUS=Shutting down..", self.log)
 
         self.stop()
 
@@ -425,6 +431,10 @@ def reexec(self):
         master_pid = os.getpid()
         self.reexec_pid = os.fork()
         if self.reexec_pid != 0:
+            # let systemd know they will be in control after exec()
+            systemd.sd_notify(
+                "RELOADING=1\nMAINPID=%d\nSTATUS=Gunicorn arbiter re-exec in forked.." % (self.reexec_pid, ), self.log
+            )
             # old master
             return
 
@@ -445,8 +455,10 @@ def reexec(self):
 
         # exec the process using the original environment
         self.log.debug("exe=%r argv=%r" % (self.START_CTX[0], self.START_CTX['args']))
-        # let systemd know are are in control
-        systemd.sd_notify("READY=1\nMAINPID=%d\nSTATUS=Gunicorn arbiter re-exec" % (master_pid, ), self.log)
+        # let systemd know we will be in control after exec()
+        systemd.sd_notify(
+            "RELOADING=1\nMAINPID=%d\nSTATUS=Gunicorn arbiter re-exec in progress.." % (os.getpid(), ), self.log
+        )
         os.execve(self.START_CTX[0], self.START_CTX['args'], environ)
 
     def reload(self):
@@ -538,8 +550,7 @@ def reap_workers(self):
                     self.reexec_pid = 0
                     self.log.info("Master exited before promotion.")
                     # let systemd know we are (back) in control
-                    systemd.sd_notify("READY=1\nMAINPID=%d\nSTATUS=Gunicorn arbiter re-exec aborted" % (os.getpid(), ), self.log)
-                    continue
+                    systemd.sd_notify("READY=1\nMAINPID=%d\nSTATUS=Old arbiter promoted" % (os.getpid(), ), self.log)
                 else:
                     worker = self.WORKERS.pop(wpid, None)
                     if not worker:

gunicorn/config.py

@@ -616,6 +616,11 @@ class Bind(Setting):
         If the ``PORT`` environment variable is defined, the default
         is ``['0.0.0.0:$PORT']``. If it is not defined, the default
         is ``['127.0.0.1:8000']``.
+
+        .. note::
+           Specifying any fd://FD socket or inheriting any socket from systemd
+           (LISTEN_FDS) results in other bind addresses to be skipped.
+           Do not mix fd://FD and systemd socket activation.
         """