supervision as supervisord does it: Postfix stopped, give-ups FATAL, reload's exit read

C-P42. postfix-script's start-fg runs master as its child and master
calls setsid() (Postfix 3.7.11, conf/postfix-script; src/master/master.c);
supervisord signals the pid alone (supervisor 4.2.5, process.py,
Subprocess.kill()). A stop of program postfix left master running - a
restart then found "already running" - and a container stop cut Postfix
off with SIGKILL. The wrapper now stays the parent of "postfix start-fg"
and on TERM/INT runs "postfix stop", asking again while start-fg is still
in its checks (master -t). stopwaitsecs=15.

C-V6. The wrapper's give-up on the milter sockets came after the default
startsecs, so it was EXITED and restarted for ever. startsecs is now
MILTER_WAIT_TIMEOUT + 10, exported by the entrypoint as POSTFIX_STARTSECS
and expanded by supervisord (options.py, processes_from_section(); a
non-number MILTER_WAIT_TIMEOUT stops the start): a give-up is "Exited too
quickly", BACKOFF, FATAL after startretries, crashexit. For those seconds
after each start the program is STARTING (the healthcheck's 90 s start
period covers it; the sender check counts no downtime then).

C-V5. logrotate had startsecs=0, so a refused config restarted it every
second for ever. startsecs=1: FATAL after startretries; crashexit reads
the event's processname and leaves logrotate's FATAL on Server > Health.

B-U2. "supervisorctl start" returns when a startsecs=0 program is RUNNING,
not when it ends, and mapped "already started" to success. The panel now
speaks supervisord's XML-RPC itself (internal/supervisor, RunOnce):
startProcess without waiting, getProcessInfo until it leaves
STARTING/RUNNING, exitstatus 0 or an error; a run in progress is waited
out and one of its own follows. A failed reload while program postfix is
not RUNNING is logged, not an error: the next master reads the files.
C-V10: postfix-reload rests EXITED after a run; the e2e process check
takes STOPPED or EXITED. C-P34: the dead "postfix set-permissions" branch
goes - postfix check's create-missing builds the queue tree.

Stand (2026-10-14, make e2e, exit 0; MILTER_WAIT_TIMEOUT=10 on the stand):
new supervision_stops_postfix_and_gives_up - supervisorctl restart postfix
writes postfix-script's "stopping the Postfix mail system" and leaves one
master; with the panel's sockets removed, start answers "postfix: ERROR
(spawn error)" (finish() sets spawnerr "Exited too quickly", onwait()
reads it first) and Postfix comes up once the panel is back; a
group-writable logrotate config ends FATAL with the container up; the
panel's Reload configuration answers only after mail.log has "refreshing
the Postfix mail system", postfix-reload EXITED. session_survives_restart
sees the stop line for the container's restart. Measured: master's own
"terminating on signal 15" never reaches mail.log (master TERMs its group,
postlogd included, before it logs). go vet and go test ./... pass on the
server (24 packages; new unit tests of RunOnce against a fake supervisord).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

build/crashexit.py

@@ -1,10 +1,12 @@
 #!/usr/bin/env python3
 """Supervisor event listener: bring the container down on unrecoverable failure.
 
-If any managed program exhausts its restart retries and enters FATAL, this
-listener signals supervisord (its parent) to terminate, so the whole container
-exits and Docker's `restart` policy can recreate it cleanly — rather than
-lingering "alive" with a dead Postfix/OpenDKIM/panel.
+If a managed program of the mail path exhausts its restart retries and
+enters FATAL, this listener signals supervisord (its parent) to terminate, so
+the whole container exits and Docker's `restart` policy starts it again —
+rather than lingering "alive" with a dead Postfix/OpenDKIM/panel. logrotate is
+not on the mail path: its FATAL (a config it would ignore) stays on
+Server > Health, and mail keeps flowing (assumptions C-V5).
 
 Communication with supervisord uses the event listener protocol over stdin and
 stdout, so stdout must carry only protocol tokens.
@@ -12,6 +14,9 @@ stdout, so stdout must carry only protocol tokens.
 supervisor 4.2.5, docs/events.rst, "Event Listener Notification Protocol": the
 listener writes READY\\n, reads one header line of key:value tokens whose len
 is the payload's length, reads the payload, and answers "RESULT 2\\nOK".
+A PROCESS_STATE_FATAL payload is a token set, "processname:cat groupname:cat
+from_state:BACKOFF" (docs/events.rst; supervisor/events.py,
+ProcessStateEvent.payload()).
 supervisord starts the listener as its own child, and on SIGTERM it shuts down
 (docs/running.rst, "Signals"); it is PID 1 here (build/entrypoint.sh, exec).
 """
@@ -19,6 +24,9 @@ import os
 import signal
 import sys
 
+# Programs whose FATAL does not take the container down (build/supervisord.conf).
+SPARED = {"logrotate"}
+
 
 def write_stdout(s):
     sys.stdout.write(s)
@@ -35,16 +43,27 @@ def main():
             return
         headers = dict(pair.split(":", 1) for pair in line.split())
         payload_len = int(headers.get("len", 0))
-        if payload_len:
-            sys.stdin.read(payload_len)
+        payload = sys.stdin.read(payload_len) if payload_len else ""
+        tokens = dict(
+            pair.split(":", 1) for pair in payload.split() if ":" in pair
+        )
+        name = tokens.get("processname", "")
 
         # We only subscribe to PROCESS_STATE_FATAL, so any event means a managed
-        # program can no longer be restarted. Take the container down.
-        sys.stderr.write(
-            "crashexit: a managed process entered FATAL; shutting down container\n"
-        )
-        sys.stderr.flush()
-        os.kill(os.getppid(), signal.SIGTERM)
+        # program can no longer be restarted.
+        if name in SPARED:
+            sys.stderr.write(
+                "crashexit: %s entered FATAL; it is not on the mail path, the "
+                "container stays up\n" % name
+            )
+            sys.stderr.flush()
+        else:
+            sys.stderr.write(
+                "crashexit: %s entered FATAL; shutting down container\n"
+                % (name or "a managed process")
+            )
+            sys.stderr.flush()
+            os.kill(os.getppid(), signal.SIGTERM)
 
         write_stdout("RESULT 2\nOK")