Fix queue_manager in a containerized environment

This patch fixes the operation of queue_manager in a
containerized environment by adding an additional check
on the start_time in ticks since boot.
This way, we can detect a restart even when the PID remains
unchanged as it is ussual in containers, but the start_time is
different.

[1] https://www.man7.org/linux/man-pages//man5/proc_pid_stat.5.html

From man page above:

(22) starttime  %llu
    The time the process started after system boot.
    Before Linux 2.6, this value was expressed in
    jiffies.  Since Linux 2.6, the value is expressed
    in clock ticks (divide by sysconf(_SC_CLK_TCK)).

Closes-Bug: #2078935
Change-Id: I9e22433ec039ad6783593d9cb7fbe22c9090534e
(cherry picked from commit 6790f702fa)

oslo_messaging/_drivers/amqpdriver.py

@@ -66,6 +66,13 @@ class QManager(object):
         # We use the process group to restart the counter on service restart
         self.pg = os.getpgrp()
 
+        # We need to also handle containerized deployments, so let's
+        # parse start time (in jiffies) since system boot
+        #
+        # https://www.man7.org/linux/man-pages//man5/proc_pid_stat.5.html
+        with open(f'/proc/{self.pg}/stat', 'r') as f:
+            self.start_time = int(f.read().split()[21])
+
     def get(self):
         lock_name = 'oslo_read_shm_%s_%s' % (self.hostname, self.processname)
 
@@ -75,28 +82,32 @@ class QManager(object):
             # This function is thread and process safe thanks to lockutils
             try:
                 with open(self.file_name, 'r') as f:
-                    pg, c = f.readline().split(':')
+                    pg, counter, start_time = f.readline().split(':')
                     pg = int(pg)
-                    c = int(c)
+                    counter = int(counter)
+                    start_time = int(start_time)
             except (FileNotFoundError, ValueError):
                 pg = self.pg
-                c = 0
+                counter = 0
+                start_time = self.start_time
 
             # Increment the counter
-            if pg == self.pg:
-                c += 1
+            if pg == self.pg and start_time == self.start_time:
+                counter += 1
             else:
-                # The process group changed, maybe service restarted?
+                # The process group is changed, or start time since system boot
+                # differs. Maybe service restarted ?
                 # Start over the counter
-                c = 1
+                counter = 1
 
             # Write the new counter
             with open(self.file_name, 'w') as f:
-                f.write(str(self.pg) + ':' + str(c))
-            return c
+                f.write(str(self.pg) + ':' + str(counter) + ':' +
+                        str(start_time))
+            return counter
 
-        c = read_from_shm()
-        return self.hostname + ":" + self.processname + ":" + str(c)
+        counter = read_from_shm()
+        return self.hostname + ":" + self.processname + ":" + str(counter)
 
 
 class MessageOperationsHandler(object):