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import os
import weakref
from datetime import datetime
from .base import SubsystemBase
from volttron.platform.messaging.headers import TIMESTAMP
from volttron.platform.agent.utils import (get_aware_utc_now,
format_timestamp)
from volttron.platform.scheduling import periodic
from ..errors import Unreachable, VIPError
"""The heartbeat subsystem adds an optional periodic publish to all agents.
Heartbeats can be started with agents and toggled on and off at runtime.
"""
__docformat__ = 'reStructuredText'
__version__ = '1.0'
[docs]class Heartbeat(SubsystemBase):
def __init__(self, owner, core, rpc, pubsub, heartbeat_autostart,
heartbeat_period):
self.owner = owner
self.core = weakref.ref(core)
self.pubsub = weakref.ref(pubsub)
self.autostart = heartbeat_autostart
self.period = heartbeat_period
self.enabled = False
self.connect_error = False
def onsetup(sender, **kwargs):
rpc.export(self.start, 'heartbeat.start')
rpc.export(self.start_with_period, 'heartbeat.start_with_period')
rpc.export(self.stop, 'heartbeat.stop')
rpc.export(self.restart, 'heartbeat.restart')
rpc.export(self.set_period, 'heartbeat.set_period')
def onstart(sender, **kwargs):
if self.autostart:
self.start()
core.onsetup.connect(onsetup, self)
core.onstart.connect(onstart, self)
core.onconnected.connect(self.reconnect)
[docs] def start(self):
"""RPC method
Starts an agent's heartbeat.
"""
if not self.enabled:
self.scheduled = self.core().schedule(periodic(self.period), self.publish)
self.enabled = True
[docs] def start_with_period(self, period):
"""RPC method
Set period and start heartbeat.
:param period: Time in seconds between publishes.
"""
self.set_period(period)
self.start()
[docs] def reconnect(self, sender, **kwargs):
if self.connect_error:
self.restart()
self.connect_error = False
[docs] def stop(self):
"""RPC method
Stop an agent's heartbeat.
"""
if self.enabled:
# Trap the fact that scheduled may not have been
# set yet if the start hasn't been called.
try:
self.scheduled.cancel()
except AttributeError:
pass
self.enabled = False
[docs] def restart(self):
"""RPC method
Restart the heartbeat with the current period. The heartbeat will
be immediately sending the heartbeat to the message bus.
"""
self.stop()
self.start()
[docs] def set_period(self, period):
"""RPC method
Set heartbeat period.
:param period: Time in seconds between publishes.
"""
if self.enabled:
self.stop()
self.period = period
self.start()
else:
self.period = period
[docs] def publish(self):
topic = 'heartbeat/' + self.core().identity
headers = {TIMESTAMP: format_timestamp(get_aware_utc_now())}
message = self.owner.vip.health.get_status_value()
try:
self.pubsub().publish('pubsub', topic, headers, message)
except Unreachable as exc:
self.connect_error = True
self.stop()