rom 18fc1239e3b5db5bd23bef6524550bc433d4730b Mon Sep 17 00:00:00 2001

From: Alexey Lebedeff <alebedev@mirantis.com>

Date: Tue, 29 Mar 2016 20:30:22 +0300

Subject: [PATCH 1/1] Don't send unasked for systemd notifications

Suppose we have some erlang system that uses systemd unit with

Type=notify - so this should send startup confirmation itself. But if

systemd-enabled epmd will be started as a first step of that system

startup, empd startup confirmation will be misinterpeted by systemd. And

our erlang service will be considered 'ready' to early. Also this will

interefere with systemd MAINPID detection: systemd will be monitoring

`epmd` process instead of `beam` one.

For example, rabbitmq works around this issue by starting epmd using

separate short-lived beam process, with NOTIFY_SOCKET environment

variable reset - only in this way we could be sure that epmd will not

interfere with rabbit startup sequence.

This patch disables indiscriminate confirmation sending, and does it

only when it was explicitly asked to do so.

---

 erts/epmd/src/epmd.c     |    6 ++++--

 erts/epmd/src/epmd_srv.c |    8 +++++---

 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/erts/epmd/src/epmd.c b/erts/epmd/src/epmd.c

index 5513cb2..4740ce8 100644

--- a/erts/epmd/src/epmd.c

+++ b/erts/epmd/src/epmd.c

@@ -592,8 +592,10 @@ void epmd_cleanup_exit(EpmdVars *g, int exitval)

       free(g->argv);

   }

 #ifdef HAVE_SYSTEMD_DAEMON

-  sd_notifyf(0, "STATUS=Exited.\n"

-                "ERRNO=%i", exitval);

+  if (g->is_systemd){

+    sd_notifyf(0, "STATUS=Exited.\n"

+               "ERRNO=%i", exitval);

+  }

 #endif /* HAVE_SYSTEMD_DAEMON */

   exit(exitval);

 }

diff --git a/erts/epmd/src/epmd_srv.c b/erts/epmd/src/epmd_srv.c

index e1bac99..59d59ad 100644

--- a/erts/epmd/src/epmd_srv.c

+++ b/erts/epmd/src/epmd_srv.c

@@ -452,9 +452,11 @@ void run(EpmdVars *g)

   num_sockets = bound;

 #ifdef HAVE_SYSTEMD_DAEMON

     }

-    sd_notifyf(0, "READY=1\n"

-                  "STATUS=Processing port mapping requests...\n"

-                  "MAINPID=%lu", (unsigned long) getpid());

+    if (g->is_systemd) {

+      sd_notifyf(0, "READY=1\n"

+                    "STATUS=Processing port mapping requests...\n"

+                    "MAINPID=%lu", (unsigned long) getpid());

+    }

 #endif /* HAVE_SYSTEMD_DAEMON */

   dbg_tty_printf(g,2,"entering the main select() loop");

-- 

1.7.3.3