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|
#!/usr/bin/python3
import asyncio
import asyncpg
import json
import logging
class JobQueue(object):
def __init__(self):
self._con = None
self._listens = {}
def _listener(self, con, pid,
channel, payload):
"""Fire the registered callback. Must not be async."""
self._listens[channel](payload)
async def _hook_listener(self):
"""Register callbacks."""
if len(self._listens.keys()) > 0:
for channel in self._listens.keys():
await self._con.add_listener(channel,
self._listener)
async def connect(self, **args):
"""Connect the database."""
logging.info("connecting to queue database")
while True:
try:
self._con = await asyncpg.connect(**args)
await self._hook_listener()
break
except asyncpg.exceptions.CannotConnectNowError:
logging.warning(
"queue database is not ready yet, retrying")
await asyncio.sleep(1)
except asyncpg.exceptions.TooManyConnectionsError:
logging.warning(
"queue database has too many clients, retrying")
await asyncio.sleep(1)
async def setup(self):
"""Initialize the database."""
await self._con.execute("""
CREATE TABLE IF NOT EXISTS
jobs (
id SERIAL PRIMARY KEY,
priority INT DEFAULT 0,
status TEXT DEFAULT 'open',
type TEXT,
payload JSONB
)
""")
await self._con.execute("""
CREATE UNIQUE INDEX
IF NOT EXISTS
jobs_priority_id_idx
ON jobs(priority, id)
""")
async def listen(self, channel, callback):
"""Hook a notification listener."""
self._listens[channel] = callback
async def request(self, jobtype, payload, priority=0):
"""Create a new job and return its id."""
if isinstance(payload, list):
payloads = [json.dumps(p)
for p in payload]
else:
payloads = [json.dumps(payload)]
if isinstance(priority, list):
priorities = priority
else:
priorities = [priority] * len(payloads)
insert = await self._con.prepare("""
INSERT INTO jobs(type, payload, priority)
VALUES($1, $2, $3)
RETURNING id
""")
ids = []
async with self._con.transaction():
for pl, pr in zip(payloads, priorities):
ids.append(await insert.fetchval(jobtype, pl, pr))
await self._con.execute("SELECT pg_notify($1 || '_open', '')",
jobtype)
if isinstance(payload, list):
return ids
else:
return ids[0]
async def acquire(self, jobtype, length=None):
"""Mark a job as running, return id, payload and priority.
Return (None, None, None) if no job is available."""
if length is None:
limit = 1
else:
limit = length
while True:
try:
# do not allow async access
async with self._con.transaction(isolation="serializable"):
result = await self._con.fetch("""
UPDATE jobs SET STATUS='running'
FROM (
SELECT id FROM jobs
WHERE status='open' AND type=$1
ORDER BY priority, id
LIMIT $2
) AS open_jobs
WHERE jobs.id=open_jobs.id
RETURNING jobs.id, jobs.payload, jobs.priority
""", jobtype, limit)
if len(result) == 0 and length is None:
# no jobs available
# backwards compatibility
return None, None, None
jobs = [(r[0], json.loads(r[1]), r[2]) for r in result]
await self._con.execute("SELECT pg_notify($1 || '_running', '')",
jobtype)
if length is None:
return jobs[0]
else:
return jobs
except asyncpg.exceptions.SerializationError:
# job is being picked up by another worker, try again
pass
async def status(self, jobid):
"""Return the status of a job."""
return await self._con.fetchval("""
SELECT status
FROM jobs WHERE
id=$1
""", jobid)
async def finish(self, jobid, jobtype):
"""Mark jobs as completed."""
if not isinstance(jobid, list):
jobids = [(jobid,)]
else:
jobids = [(jid,) for jid in jobid]
async with self._con.transaction():
await self._con.executemany("""
UPDATE jobs SET status='finished'
WHERE id=$1
""", jobids)
await self._con.execute("""
SELECT pg_notify($1 || '_finished', '')
""", jobtype)
async def fail(self, jobid, jobtype, reason):
"""Mark a job as failed."""
if not isinstance(jobid, list):
jobids = [jobid]
else:
jobids = jobid
if not isinstance(reason, list):
reasons = [json.dumps({"error": reason})]
else:
reasons = [json.dumps({"error": r})
for r in reason]
assert len(jobids) == len(reasons)
async with self._con.transaction():
await self._con.executemany("""
UPDATE jobs SET status='failed',
payload=payload||$2::jsonb
WHERE id=$1
""", zip(jobids, reasons))
await self._con.execute("""
SELECT pg_notify($1 || '_failed', '')
""", jobtype)
async def reset(self, jobid, jobtype):
"""Mark a job as open."""
if not isinstance(jobid, list):
jobids = [(jobid,)]
else:
jobids = [(jid,) for jid in jobid]
async with self._con.transaction():
await self._con.executemany("""
UPDATE jobs SET status='open'
WHERE id=$1
""", jobids)
await self._con.execute("""
SELECT pg_notify($1 || '_open', '')
""", jobtype)
async def cleanup(self):
"""Reopen all unfinished jobs."""
while True:
try:
async with self._con.transaction(isolation="serializable"):
await self._con.execute("""
UPDATE jobs
SET status='open'
WHERE status='running'
""")
return
except asyncpg.exceptions.SerializationError:
pass
|
