#!/usr/bin/env python # vim: set sw=4 et: import logging import time import threading import kombu import socket from umbra.browser import BrowserPool, BrowsingException class AmqpBrowserController: """ Consumes amqp messages representing requests to browse urls, from the specified amqp queue (default: "urls") on the specified amqp exchange (default: "umbra"). Incoming amqp message is a json object with 3 attributes: { "clientId": "umbra.client.123", "url": "http://example.com/my_fancy_page", "metadata": {"arbitrary":"fields", "etc":4} } "url" is the url to browse. "clientId" uniquely identifies the client of umbra. Umbra uses the clientId as the amqp routing key, to direct information via amqp back to the client. It sends this information on the same specified amqp exchange (default: "umbra"). Each url requested in the browser is published to amqp this way. The outgoing amqp message is a json object: { "url": "http://example.com/images/embedded_thing.jpg", "method": "GET", "headers": {"User-Agent": "...", "Accept": "...", ...}, "parentUrl": "http://example.com/my_fancy_page", "parentUrlMetadata": {"arbitrary":"fields", "etc":4, ...} } POST requests have an additional field, postData. """ logger = logging.getLogger(__module__ + "." + __qualname__) def __init__(self, amqp_url='amqp://guest:guest@localhost:5672/%2f', chrome_exe='chromium-browser', max_active_browsers=1, queue_name='urls', exchange_name='umbra'): self.amqp_url = amqp_url self.queue_name = queue_name self.exchange_name = exchange_name self._browser_pool = BrowserPool(size=max_active_browsers, chrome_exe=chrome_exe) def start(self): self._browsing_threads = set() self._browsing_threads_lock = threading.Lock() self._exchange = kombu.Exchange(name=self.exchange_name, type='direct', durable=True) self._producer = None self._producer_lock = threading.Lock() with self._producer_lock: self._producer_conn = kombu.Connection(self.amqp_url) self._producer = self._producer_conn.Producer(serializer='json') self._consumer_thread = threading.Thread(target=self._consume_amqp, name='AmqpConsumerThread') self._consumer_stop = threading.Event() self._consumer_thread.start() def shutdown(self): self.logger.info("shutting down amqp consumer {}".format(self.amqp_url)) self._consumer_stop.set() self._consumer_thread.join() def shutdown_now(self): self._consumer_stop.set() self._browser_pool.shutdown_now() self._consumer_thread.join() def _wait_for_and_browse_urls(self, conn, consumer, timeout): start = time.time() browser = None consumer.qos(prefetch_count=1) while not self._consumer_stop.is_set() and time.time() - start < timeout: try: browser = self._browser_pool.acquire() # raises KeyError if none available browser.start() def callback(body, message): self._start_browsing_page(browser, message, body['clientId'], body['url'], body['metadata']) consumer.callbacks = [callback] while True: try: conn.drain_events(timeout=0.5) break # out of "while True" to acquire another browser except socket.timeout: pass if self._consumer_stop.is_set() or time.time() - start >= timeout: browser.stop() self._browser_pool.release(browser) break except KeyError: # no browsers available time.sleep(0.5) except: self.logger.critical("problem with browser initialization", exc_info=True) time.sleep(0.5) finally: consumer.callbacks = None def _wait_for_active_browsers(self): self.logger.info("waiting for browsing threads to finish") while True: with self._browsing_threads_lock: if len(self._browsing_threads) == 0: break time.sleep(0.5) self.logger.info("active browsing threads finished") def _consume_amqp(self): # XXX https://webarchive.jira.com/browse/ARI-3811 # After running for some amount of time (3 weeks in the latest case), # consumer looks normal but doesn't consume any messages. Not clear if # it's hanging in drain_events() or not. As a temporary measure for # mitigation (if it works) or debugging (if it doesn't work), close and # reopen the connection every 2.5 hours RECONNECT_AFTER_SECONDS = 150 * 60 url_queue = kombu.Queue(self.queue_name, exchange=self._exchange) while not self._consumer_stop.is_set(): try: self.logger.info("connecting to amqp exchange={} at {}".format(self._exchange.name, self.amqp_url)) with kombu.Connection(self.amqp_url) as conn: with conn.Consumer(url_queue) as consumer: self._wait_for_and_browse_urls(conn, consumer, timeout=RECONNECT_AFTER_SECONDS) # need to wait for browsers to finish here, before closing # the amqp connection, because they use it to do # message.ack() after they finish browsing a page self._wait_for_active_browsers() except BaseException as e: self.logger.error("caught exception {}".format(e), exc_info=True) time.sleep(0.5) self.logger.error("attempting to reopen amqp connection") def _start_browsing_page(self, browser, message, client_id, url, parent_url_metadata): def on_request(chrome_msg): payload = chrome_msg['params']['request'] payload['parentUrl'] = url payload['parentUrlMetadata'] = parent_url_metadata self.logger.debug('sending to amqp exchange={} routing_key={} payload={}'.format(self.exchange_name, client_id, payload)) with self._producer_lock: publish = self._producer_conn.ensure(self._producer, self._producer.publish) publish(payload, exchange=self._exchange, routing_key=client_id) def browse_page_sync(): self.logger.info('browser={} client_id={} url={}'.format(browser, client_id, url)) try: browser.browse_page(url, on_request=on_request) message.ack() except BrowsingException as e: self.logger.warn("browsing did not complete normally, requeuing url {} - {}".format(url, e)) message.requeue() except: self.logger.critical("problem browsing page, requeuing url {}, may have lost browser process".format(url), exc_info=True) message.requeue() finally: browser.stop() self._browser_pool.release(browser) def browse_thread_run_then_cleanup(): browse_page_sync() with self._browsing_threads_lock: self._browsing_threads.remove(threading.current_thread()) import random thread_name = "BrowsingThread{}-{}".format(browser.chrome_port, ''.join((random.choice('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789') for _ in range(6)))) th = threading.Thread(target=browse_thread_run_then_cleanup, name=thread_name) with self._browsing_threads_lock: self._browsing_threads.add(th) th.start()