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import json
import time
from pykafka.common import OffsetType
from .worker_common import FatcatWorker, most_recent_message
class ChangelogWorker(FatcatWorker):
"""
Periodically polls the fatcat API looking for new changelogs. When they are
found, fetch them and push (as JSON) into a Kafka topic.
"""
def __init__(self, api, kafka_hosts, produce_topic, poll_interval=10.0, offset=None):
# TODO: should be offset=0
super().__init__(kafka_hosts=kafka_hosts,
produce_topic=produce_topic,
api=api)
self.poll_interval = poll_interval
self.offset = offset # the fatcat changelog offset, not the kafka offset
def run(self):
topic = self.kafka.topics[self.produce_topic]
# On start, try to consume the most recent from the topic, and using
# that as the starting offset. Note that this is a single-partition
# topic
if self.offset is None:
print("Checking for most recent changelog offset...")
msg = most_recent_message(topic)
if msg:
self.offset = json.loads(msg.decode('utf-8'))['index']
else:
self.offset = 1
with topic.get_producer(
max_request_size=self.produce_max_request_size,
) as producer:
while True:
latest = int(self.api.get_changelog(limit=1)[0].index)
if latest > self.offset:
print("Fetching changelogs from {} through {}".format(
self.offset+1, latest))
for i in range(self.offset+1, latest+1):
cle = self.api.get_changelog_entry(i)
obj = self.api.api_client.sanitize_for_serialization(cle)
producer.produce(
message=json.dumps(obj).encode('utf-8'),
partition_key=None,
timestamp=None,
#NOTE could be (???): timestamp=cle.timestamp,
)
self.offset = i
print("Sleeping {} seconds...".format(self.poll_interval))
time.sleep(self.poll_interval)
class EntityUpdatesWorker(FatcatWorker):
"""
Consumes from the changelog topic and publishes expanded entities (fetched
from API) to update topics.
For now, only release updates are published.
"""
def __init__(self, api, kafka_hosts, consume_topic, release_topic, file_topic, container_topic):
super().__init__(kafka_hosts=kafka_hosts,
consume_topic=consume_topic,
api=api)
self.release_topic = release_topic
self.file_topic = file_topic
self.container_topic = container_topic
self.consumer_group = "entity-updates"
def run(self):
changelog_topic = self.kafka.topics[self.consume_topic]
release_topic = self.kafka.topics[self.release_topic]
file_topic = self.kafka.topics[self.file_topic]
container_topic = self.kafka.topics[self.container_topic]
consumer = changelog_topic.get_balanced_consumer(
consumer_group=self.consumer_group,
managed=True,
auto_offset_reset=OffsetType.LATEST,
reset_offset_on_start=False,
fetch_message_max_bytes=4000000, # up to ~4MBytes
auto_commit_enable=True,
auto_commit_interval_ms=30000, # 30 seconds
compacted_topic=True,
)
# using a sync producer to try and avoid racey loss of delivery (aka,
# if consumer group updated but produce didn't stick)
release_producer = release_topic.get_sync_producer(
max_request_size=self.produce_max_request_size,
)
file_producer = file_topic.get_sync_producer(
max_request_size=self.produce_max_request_size,
)
container_producer = container_topic.get_sync_producer(
max_request_size=self.produce_max_request_size,
)
for msg in consumer:
cle = json.loads(msg.value.decode('utf-8'))
#print(cle)
print("processing changelog index {}".format(cle['index']))
release_ids = []
file_ids = []
container_ids = []
work_ids = []
release_edits = cle['editgroup']['edits']['releases']
for re in release_edits:
release_ids.append(re['ident'])
file_edits = cle['editgroup']['edits']['files']
for e in file_edits:
file_ids.append(e['ident'])
container_edits = cle['editgroup']['edits']['containers']
for e in container_edits:
container_ids.append(e['ident'])
work_edits = cle['editgroup']['edits']['works']
for e in work_edits:
work_ids.append(e['ident'])
# TODO: do these fetches in parallel using a thread pool?
for ident in set(file_ids):
file_entity = self.api.get_file(ident, expand=None)
# update release when a file changes
# TODO: fetch old revision as well, and only update
# releases for which list changed
release_ids.extend(e['release_ids'])
file_dict = self.api.api_client.sanitize_for_serialization(file_entity)
file_producer.produce(
message=json.dumps(file_dict).encode('utf-8'),
partition_key=ident.encode('utf-8'),
timestamp=None,
)
for ident in set(container_ids):
container = self.api.get_container(ident)
container_dict = self.api.api_client.sanitize_for_serialization(container)
container_producer.produce(
message=json.dumps(container_dict).encode('utf-8'),
partition_key=ident.encode('utf-8'),
timestamp=None,
)
for ident in set(release_ids):
release = self.api.get_release(ident, expand="files,filesets,webcaptures,container")
work_ids.append(release.work_id)
release_dict = self.api.api_client.sanitize_for_serialization(release)
release_producer.produce(
message=json.dumps(release_dict).encode('utf-8'),
partition_key=ident.encode('utf-8'),
timestamp=None,
)
# TODO: actually update works
#consumer.commit_offsets()
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