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34eb083836
* Plugin architecture for messaging fabric * Schemas use a technology neutral expression * Schemas strictness has uncovered some incorrect schema use which is fixed
283 lines
8.4 KiB
Python
283 lines
8.4 KiB
Python
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# Base class for processors. Implements:
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# - Pulsar client, subscribe and consume basic
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# - the async startup logic
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# - Initialising metrics
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import asyncio
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import argparse
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import _pulsar
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import time
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import uuid
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import logging
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import os
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from prometheus_client import start_http_server, Info
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from .. schema import ConfigPush, config_push_queue
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from .. log_level import LogLevel
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from . pubsub import PulsarClient, get_pubsub
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from . producer import Producer
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from . consumer import Consumer
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from . metrics import ProcessorMetrics, ConsumerMetrics
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from . logging import add_logging_args, setup_logging
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default_config_queue = config_push_queue
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# Module logger
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logger = logging.getLogger(__name__)
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# Async processor
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class AsyncProcessor:
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def __init__(self, **params):
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# Store the identity
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self.id = params.get("id")
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# Create pub/sub backend via factory
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self.pubsub_backend = get_pubsub(**params)
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# Store pulsar_host for backward compatibility
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self._pulsar_host = params.get("pulsar_host", "pulsar://pulsar:6650")
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# Initialise metrics, records the parameters
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ProcessorMetrics(processor = self.id).info({
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k: str(params[k])
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for k in params
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if k != "id"
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})
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# The processor runs all activity in a taskgroup, it's mandatory
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# that this is provded
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self.taskgroup = params.get("taskgroup")
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if self.taskgroup is None:
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raise RuntimeError("Essential taskgroup missing")
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# Get the configuration topic
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self.config_push_queue = params.get(
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"config_push_queue", default_config_queue
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)
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# This records registered configuration handlers
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self.config_handlers = []
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# Create a random ID for this subscription to the configuration
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# service
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config_subscriber_id = str(uuid.uuid4())
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config_consumer_metrics = ConsumerMetrics(
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processor = self.id, flow = None, name = "config",
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)
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# Subscribe to config queue
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self.config_sub_task = Consumer(
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taskgroup = self.taskgroup,
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backend = self.pubsub_backend, # Changed from client to backend
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subscriber = config_subscriber_id,
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flow = None,
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topic = self.config_push_queue,
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schema = ConfigPush,
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handler = self.on_config_change,
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metrics = config_consumer_metrics,
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# This causes new subscriptions to view the entire history of
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# configuration
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start_of_messages = True
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)
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self.running = True
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# This is called to start dynamic behaviour. An over-ride point for
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# extra functionality
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async def start(self):
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await self.config_sub_task.start()
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# This is called to stop all threads. An over-ride point for extra
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# functionality
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def stop(self):
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self.pubsub_backend.close()
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self.running = False
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# Returns the pub/sub backend (new interface)
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@property
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def pubsub(self): return self.pubsub_backend
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# Returns the pulsar host (backward compatibility)
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@property
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def pulsar_host(self): return self._pulsar_host
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# Register a new event handler for configuration change
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def register_config_handler(self, handler):
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self.config_handlers.append(handler)
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# Called when a new configuration message push occurs
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async def on_config_change(self, message, consumer, flow):
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# Get configuration data and version number
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config = message.value().config
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version = message.value().version
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# Invoke message handlers
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logger.info(f"Config change event: version={version}")
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for ch in self.config_handlers:
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await ch(config, version)
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# This is the 'main' body of the handler. It is a point to override
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# if needed. By default does nothing. Processors are implemented
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# by adding consumer/producer functionality so maybe nothing is needed
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# in the run() body
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async def run(self):
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while self.running:
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await asyncio.sleep(2)
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# Startup fabric. This runs in 'async' mode, creates a taskgroup and
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# runs the producer.
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@classmethod
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async def launch_async(cls, args):
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try:
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# Create a taskgroup. This seems complicated, when an exception
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# occurs, unhandled it looks like it cancels all threads in the
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# taskgroup. Needs the exception to be caught in the right
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# place.
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async with asyncio.TaskGroup() as tg:
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# Create a processor instance, and include the taskgroup
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# as a paramter. A processor identity ident is used as
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# - subscriber name
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# - an identifier for flow configuration
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p = cls(**args | { "taskgroup": tg })
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# Start the processor
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await p.start()
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# Run the processor
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task = tg.create_task(p.run())
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# The taskgroup causes everything to wait until
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# all threads have stopped
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# This is here to output a debug message, shouldn't be needed.
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except Exception as e:
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logger.error("Exception, closing taskgroup", exc_info=True)
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raise e
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@classmethod
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def setup_logging(cls, args):
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"""Configure logging for the entire application"""
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setup_logging(args)
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# Startup fabric. launch calls launch_async in async mode.
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@classmethod
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def launch(cls, ident, doc):
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# Start assembling CLI arguments
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parser = argparse.ArgumentParser(
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prog=ident,
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description=doc
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)
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parser.add_argument(
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'--id',
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default=ident,
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help=f'Configuration identity (default: {ident})',
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)
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# Invoke the class-specific add_args, which manages adding all the
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# command-line arguments
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cls.add_args(parser)
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# Parse arguments
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args = parser.parse_args()
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args = vars(args)
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# Setup logging before anything else
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cls.setup_logging(args)
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# Debug
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logger.debug(f"Arguments: {args}")
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# Start the Prometheus metrics service if needed
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if args["metrics"]:
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start_http_server(args["metrics_port"])
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# Loop forever, exception handler
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while True:
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logger.info("Starting...")
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try:
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# Launch the processor in an asyncio handler
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asyncio.run(cls.launch_async(
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args
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))
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except KeyboardInterrupt:
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logger.info("Keyboard interrupt.")
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return
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except _pulsar.Interrupted:
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logger.info("Pulsar Interrupted.")
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return
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# Exceptions from a taskgroup come in as an exception group
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except ExceptionGroup as e:
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logger.error("Exception group:")
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for se in e.exceptions:
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logger.error(f" Type: {type(se)}")
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logger.error(f" Exception: {se}", exc_info=se)
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except Exception as e:
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logger.error(f"Type: {type(e)}")
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logger.error(f"Exception: {e}", exc_info=True)
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# Retry occurs here
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logger.warning("Will retry...")
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time.sleep(4)
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logger.info("Retrying...")
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# The command-line arguments are built using a stack of add_args
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# invocations
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@staticmethod
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def add_args(parser):
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# Pub/sub backend selection
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parser.add_argument(
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'--pubsub-backend',
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default=os.getenv('PUBSUB_BACKEND', 'pulsar'),
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choices=['pulsar', 'mqtt'],
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help='Pub/sub backend (default: pulsar, env: PUBSUB_BACKEND)',
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)
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PulsarClient.add_args(parser)
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add_logging_args(parser)
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parser.add_argument(
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'--config-push-queue',
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default=default_config_queue,
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help=f'Config push queue (default: {default_config_queue})',
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)
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parser.add_argument(
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'--metrics',
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action=argparse.BooleanOptionalAction,
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default=True,
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help=f'Metrics enabled (default: true)',
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)
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parser.add_argument(
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'-P', '--metrics-port',
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type=int,
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default=8000,
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help=f'Pulsar host (default: 8000)',
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)
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