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Viewing changes to database/schema/preflight.py

  • Committer: Stuart Bishop
  • Date: 2011-07-25 12:52:15 UTC
  • mto: (7675.1045.660 db-devel)
  • mto: This revision was merged to the branch mainline in revision 13516.
  • Revision ID: stuart.bishop@canonical.com-20110725125215-3bikrwvdyamkwdql
Fragile user check for connections we don't want to risk interrupting

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database/schema/preflight.py
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# Ignore connections by these users.
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SYSTEM_USERS = frozenset(['postgres', 'slony', 'nagios', 'lagmon'])
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# Fail checks if these users are connected. If a process should not be
 
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# interrupted by a rollout, the database user it connects as should be
 
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# added here. The preflight check will fail if any of these users are
 
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# connected, so these systems will need to be shut down manually before
 
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# a database update.
 
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FRAGILE_USERS = frozenset(['archivepublisher'])
 
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# How lagged the cluster can be before failing the preflight check.
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MAX_LAG = timedelta(seconds=45)
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            self.log.info("Only system users connected to the cluster")
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        return success
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    def check_fragile_connections(self):
 
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        """Fail if any FRAGILE_USERS are connected to the cluster.
 
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        If we interrupt these processes, we may have a mess to clean
 
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        up. If they are connected, the preflight check should fail.
 
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        """
 
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        success = True
 
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        for node in self.lpmain_nodes:
 
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            cur = node.con.cursor()
 
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            cur.execute("""
 
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                SELECT datname, usename, COUNT(*) AS num_connections
 
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                FROM pg_stat_activity
 
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                WHERE
 
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                    datname=current_database()
 
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                    AND procpid <> pg_backend_pid()
 
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                    AND usename IN %s
 
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                GROUP BY datname, usename
 
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                """ % sqlvalues(FRAGILE_USERS))
 
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            for datname, usename, num_connections in cur.fetchall():
 
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                self.log.fatal(
 
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                    "Fragile system %s running. %s has %d connections.",
 
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                    usename, datname, num_connections)
 
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                success = False
 
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        if success:
 
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            self.log.info(
 
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                "No fragile systems connected to the cluster (%s)"
 
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                % ', '.join(FRAGILE_USERS))
 
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        return success
 
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    def check_long_running_transactions(self, max_secs=10):
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        """Return False if any nodes have long running transactions open.
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            return False
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        success = True
 
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        if not self.check_replication_lag():
 
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            success = False
 
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        if not self.check_can_sync():
 
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            success = False
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        if not self.check_open_connections():
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            success = False
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        if not self.check_long_running_transactions():
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            success = False
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        if not self.check_replication_lag():
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            success = False
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        if not self.check_can_sync():
 
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        if not self.check_fragile_connections():
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            success = False
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        return success
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