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hooks/hooks.py
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            return None
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        log("Election in progress")
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        winner = hookenv.local_unit()
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        winning_offset = local_state['wal_received_offset']
 
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        winner = None
 
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        winning_offset = -1
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        for relid in hookenv.relation_ids('replication'):
 
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            candidates = set(hookenv.related_units(relid))
 
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            candidates.add(hookenv.local_unit())
 
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            candidates.discard(former_master)
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            # Sort the unit lists so we get consistent results in a tie
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            # and lowest unit number wins.
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            for unit in unit_sorted(hookenv.related_units(relid)):
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                if unit == former_master:
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                    continue
 
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            for unit in unit_sorted(candidates):
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                relation = hookenv.relation_get(unit=unit, rid=relid)
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                if int(relation['wal_received_offset']) > winning_offset:
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                    winner = unit
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    elif master == hookenv.local_unit():
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        if local_state['state'] != 'master':
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            log("I have been elected master")
 
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            log("I have elected myself master")
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            promote_database()
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            if 'following' in local_state:
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                del local_state['following']
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        master_ip = hookenv.relation_get('private-address', master)
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        wait_for_db(db='postgres', user='juju_replication', host=master_ip)
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        clone(master, master_ip)
 
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        clone_database(master, master_ip)
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        local_state['state'] = 'hot standby'
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        local_state['following'] = master
 
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        if 'wal_received_offset' in local_state:
 
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            del local_state['wal_received_offset']
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    elif local_state['following'] == master:
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        log("I am a hot standby already following {}".format(master))
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            'replication_password', master)
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        generate_pgpass()
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        follow_database(master)
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        run_sql_as_postgres("SELECT pg_xlog_replay_resume()")
 
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        if not local_state["paused_at_failover"]:
 
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            run_sql_as_postgres("SELECT pg_xlog_replay_resume()")
 
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        local_state['state'] = 'hot standby'
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        local_state['following'] = master
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        del local_state['wal_received_offset']
 
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        del local_state['paused_at_failover']
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    if local_state['state'] == 'hot standby':
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        publish_hot_standby_credentials()
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        # election, and publish that replay point. By comparing these
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        # replay points, the most up to date hot standby can be
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        # identified and promoted to the new master.
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        run_sql_as_postgres("SELECT pg_xlog_replay_pause()")
 
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        cur = db_cursor(autocommit=True)
 
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        cur.execute(
 
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            "SELECT pg_is_xlog_replay_paused()")
 
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        already_paused = cur.fetchone()[0]
 
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        local_state["paused_at_failover"] = already_paused
 
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        if not already_paused:
 
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            cur.execute("SELECT pg_xlog_replay_pause()")
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        local_state['state'] = 'failover'
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        local_state['wal_received_offset'] = postgresql_wal_received_offset()
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    config_changed(postgresql_config)
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def clone(master_unit, master_host):
 
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def clone_database(master_unit, master_host):
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    postgresql_stop()
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    juju_log(MSG_INFO, "Cloning master {}".format(master_unit))
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