Using OCS Feeds --------------- Our Agent stores both the text given to the print Task, as well as the current count in the count Process, in each Operation's respective ``session.data`` object. This can be inspected by Clients on the network, but only when the Clients actively inspect the object. OCS Feeds allow us to publish data to the network, ensuring any 'subscriber' to the Feed gets a copy of the data. In practice this means the HK Aggregator and/or InfluxDB Publisher Agents. These will subscribe to any OCS Feed and record data published to those feeds in either .g3 files (in the case of the HK Aggregator) or to the InfluxDB. To add an OCS Feed we need to register the Feed in the Agent's ``__init__`` method: .. code-block:: python # Register OCS feed agg_params = { 'frame_length': 10 * 60 # [sec] } self.agent.register_feed('feed_name', record=True, agg_params=agg_params, buffer_time=1.) We then make some small modifications to the main actions in the Process, format a message to publish to the Feed, then actually publish the data: .. code-block:: python # Perform the process actions counter += 1 self.log.debug(f"{counter}! Ah! Ah! Ah!") now = time.time() session.data = {"value": counter, "timestamp": now} # Format message for publishing to Feed message = {'block_name': 'count', 'timestamp': now, 'data': {'value': counter}} self.agent.publish_to_feed('feed_name', message) time.sleep(1) Feeds have a built in buffer (which we configured to be 1 second long). Before exiting a Process the buffer should be flushed: .. code-block:: python self.agent.feeds['feed_name'].flush_buffer() We won't see any change in the logs, however if you have Grafana or ocs-web setup you can inspect the data published to the Feed. Agent Code `````````` Our Agent in full now looks like this: .. code-block:: python import time import txaio from os import environ from ocs import ocs_agent, site_config from ocs.ocs_twisted import TimeoutLock class BarebonesAgent: """Barebone Agent demonstrating writing an Agent from scratch. This Agent is meant to be an example for Agent development, and provides a clean starting point when developing a new Agent. Parameters: agent (OCSAgent): OCSAgent object from :func:`ocs.ocs_agent.init_site_agent`. Attributes: agent (OCSAgent): OCSAgent object from :func:`ocs.ocs_agent.init_site_agent`. log (txaio.tx.Logger): Logger object used to log events within the Agent. lock (TimeoutLock): TimeoutLock object used to prevent simultaneous commands being sent to hardware. _count (bool): Internal tracking of whether the Agent should be counting or not. This is used to exit the Process loop by changing it to False via the count.stop() command. Your Agent won't use this exact attribute, but might have a similar one. """ def __init__(self, agent): self.agent = agent self.log = agent.log self.lock = TimeoutLock(default_timeout=5) self._count = False # Register OCS feed agg_params = { 'frame_length': 10 * 60 # [sec] } self.agent.register_feed('feed_name', record=True, agg_params=agg_params, buffer_time=1.) def count(self, session, params): """count(test_mode=False) **Process** - Count up from 0. The count will restart if the process is stopped and restarted. Notes: The most recent value is stored in the session data object in the format:: >>> response.session['data'] {"value": 0, "timestamp":1600448753.9288929} """ with self.lock.acquire_timeout(timeout=0, job='count') as acquired: if not acquired: print("Lock could not be acquired because it " + f"is held by {self.lock.job}") return False # Initialize last release time for lock last_release = time.time() # Initialize the counter self._count=True counter = 0 self.log.info("Starting the count!") # Main process loop while self._count: # About every second, release and acquire the lock if time.time() - last_release > 1.: last_release = time.time() if not self.lock.release_and_acquire(timeout=10): print(f"Could not re-acquire lock now held by {self.lock.job}.") return False # Perform the process actions counter += 1 self.log.debug(f"{counter}! Ah! Ah! Ah!") now = time.time() session.data = {"value": counter, "timestamp": now} # Format message for publishing to Feed message = {'block_name': 'count', 'timestamp': now, 'data': {'value': counter}} self.agent.publish_to_feed('feed_name', message) time.sleep(1) self.agent.feeds['feed_name'].flush_buffer() return True, 'Acquisition exited cleanly.' def _stop_count(self, session, params): """Stop monitoring the turbo output.""" if self._count: self._count = False return True, 'requested to stop taking data.' else: return False, 'count is not currently running' @ocs_agent.param('text', default='hello world', type=str) def print(self, session, params): """print(text='hello world') **Task** - Print some text passed to a Task. Args: text (str): Text to print out. Defaults to 'hello world'. Notes: The session data will be updated with the text:: >>> response.session['data'] {'text': 'hello world', 'last_updated': 1660249321.8729222} """ with self.lock.acquire_timeout(timeout=3.0, job='print') as acquired: if not acquired: self.log.warn("Lock could not be acquired because it " + f"is held by {self.lock.job}") return False # Log the text provided to the Agent logs self.log.info(f"{params['text']}") # Store the text provided in session.data session.data = {'text': params['text'], 'last_updated': time.time()} # bool, 'descriptive text message' # True if task succeeds, False if not return True, 'Printed text to logs' def main(args=None): # For logging txaio.use_twisted() LOG = txaio.make_logger() # Start logging txaio.start_logging(level=environ.get("LOGLEVEL", "info")) args = site_config.parse_args(agent_class='BarebonesAgent', args=args) agent, runner = ocs_agent.init_site_agent(args) barebone = BarebonesAgent(agent) agent.register_process( 'count', barebone.count, barebone._stop_count) agent.register_task('print', barebone.print) runner.run(agent, auto_reconnect=True) if __name__ == '__main__': main() Running the Agent ````````````````` Running the Agent remains unchanged, except now the data will be published on an OCS Feed. We can inspect the feed on the commandline using the ``ocs-client-cli``: .. code-block:: $ OCS_CONFIG_DIR=/path/to/your/ocs-site-config/ ocs-client-cli listen observatory.barebones1.feeds.feed_name Subscribing to observatory.barebones1.feeds.feed_name 2022-07-27T01:30:02+0000 [observatory.barebones1.feeds.feed_name] [{'count': {'block_name': 'count', 'data': {'value': [51, 52]}, 'timestamps': [1658885401.7566712, 1658885402.7578506]}}, {'agent_address': 'observatory.barebones1', 'agg_params': {'frame_length': 600}, 'feed_name': 'feed_name', 'address': 'observatory.barebones1.feeds.feed_name', 'record': True, 'session_id': '1658885340.4431145', 'agent_class': 'BarebonesAgent'}] 2022-07-27T01:30:04+0000 [observatory.barebones1.feeds.feed_name] [{'count': {'block_name': 'count', 'data': {'value': [53, 54]}, 'timestamps': [1658885403.7590535, 1658885404.7613802]}}, {'agent_address': 'observatory.barebones1', 'agg_params': {'frame_length': 600}, 'feed_name': 'feed_name', 'address': 'observatory.barebones1.feeds.feed_name', 'record': True, 'session_id': '1658885340.4431145', 'agent_class': 'BarebonesAgent'}] 2022-07-27T01:30:06+0000 [observatory.barebones1.feeds.feed_name] [{'count': {'block_name': 'count', 'data': {'value': [55, 56]}, 'timestamps': [1658885405.7625823, 1658885406.7638052]}}, {'agent_address': 'observatory.barebones1', 'agg_params': {'frame_length': 600}, 'feed_name': 'feed_name', 'address': 'observatory.barebones1.feeds.feed_name', 'record': True, 'session_id': '1658885340.4431145', 'agent_class': 'BarebonesAgent'}] Here we see the values (51, 52, 53, 54, 55, and 56) published to the OCS Feed. Next, we will add an argument to our Agent and configure it to be passed at startup in our SCF.