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backend.py
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backend.py
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# Copyright (C) 2015 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information
import binascii
import datetime
from functools import wraps
import json
import tempfile
from arrow import Arrow, utcnow
import psycopg2
import psycopg2.extras
from psycopg2.extensions import AsIs
from swh.core.config import SWHConfig
def adapt_arrow(arrow):
return AsIs("'%s'::timestamptz" % arrow.isoformat())
psycopg2.extensions.register_adapter(dict, psycopg2.extras.Json)
psycopg2.extensions.register_adapter(Arrow, adapt_arrow)
def autocommit(fn):
@wraps(fn)
def wrapped(self, *args, **kwargs):
autocommit = False
if 'cursor' not in kwargs or not kwargs['cursor']:
autocommit = True
kwargs['cursor'] = self.cursor()
try:
ret = fn(self, *args, **kwargs)
except Exception:
if autocommit:
self.rollback()
raise
if autocommit:
self.commit()
return ret
return wrapped
class SchedulerBackend(SWHConfig):
"""
Backend for the Software Heritage scheduling database.
"""
CONFIG_BASE_FILENAME = 'scheduler.ini'
DEFAULT_CONFIG = {
'scheduling_db': ('str', 'dbname=softwareheritage-scheduler-dev'),
}
def __init__(self, **override_config):
self.config = self.parse_config_file(global_config=False)
self.config.update(override_config)
self.db = None
self.reconnect()
def reconnect(self):
if not self.db or self.db.closed:
self.db = psycopg2.connect(
dsn=self.config['scheduling_db'],
cursor_factory=psycopg2.extras.RealDictCursor,
)
def cursor(self):
"""Return a fresh cursor on the database, with auto-reconnection in case of
failure"""
cur = None
# Get a fresh cursor and reconnect at most three times
tries = 0
while True:
tries += 1
try:
cur = self.db.cursor()
cur.execute('select 1')
break
except psycopg2.OperationalError:
if tries < 3:
self.reconnect()
else:
raise
return cur
def commit(self):
"""Commit a transaction"""
self.db.commit()
def rollback(self):
"""Rollback a transaction"""
self.db.rollback()
def copy_to(self, items, tblname, columns, cursor=None, item_cb=None):
def escape(data):
if data is None:
return ''
if isinstance(data, bytes):
return '\\x%s' % binascii.hexlify(data).decode('ascii')
elif isinstance(data, str):
return '"%s"' % data.replace('"', '""')
elif isinstance(data, (datetime.datetime, Arrow)):
# We escape twice to make sure the string generated by
# isoformat gets escaped
return escape(data.isoformat())
elif isinstance(data, dict):
return escape(json.dumps(data))
elif isinstance(data, list):
return escape("{%s}" % ','.join(escape(d) for d in data))
elif isinstance(data, psycopg2.extras.Range):
# We escape twice here too, so that we make sure
# everything gets passed to copy properly
return escape(
'%s%s,%s%s' % (
'[' if data.lower_inc else '(',
'-infinity' if data.lower_inf else escape(data.lower),
'infinity' if data.upper_inf else escape(data.upper),
']' if data.upper_inc else ')',
)
)
else:
# We don't escape here to make sure we pass literals properly
return str(data)
with tempfile.TemporaryFile('w+') as f:
for d in items:
if item_cb is not None:
item_cb(d)
line = [escape(d.get(k)) for k in columns]
f.write(','.join(line))
f.write('\n')
f.seek(0)
cursor.copy_expert('COPY %s (%s) FROM STDIN CSV' % (
tblname, ', '.join(columns)), f)
task_type_keys = [
'type', 'description', 'backend_name', 'default_interval',
'min_interval', 'max_interval', 'backoff_factor', 'max_queue_length',
'num_retries', 'retry_delay',
]
def _format_query(self, query, keys):
"""Format a query with the given keys"""
query_keys = ', '.join(keys)
placeholders = ', '.join(['%s'] * len(keys))
return query.format(keys=query_keys, placeholders=placeholders)
def _format_multiquery(self, query, keys, values):
"""Format a query with placeholders generated for multiple values"""
query_keys = ', '.join(keys)
placeholders = '), ('.join(
[', '.join(['%s'] * len(keys))] * len(values)
)
ret_values = sum([[value[key] for key in keys]
for value in values], [])
return (
query.format(keys=query_keys, placeholders=placeholders),
ret_values,
)
@autocommit
def create_task_type(self, task_type, cursor=None):
"""Create a new task type ready for scheduling.
Args:
task_type (dict): a dictionary with the following keys:
- type (str): an identifier for the task type
- description (str): a human-readable description of what the
task does
- backend_name (str): the name of the task in the
job-scheduling backend
- default_interval (datetime.timedelta): the default interval
between two task runs
- min_interval (datetime.timedelta): the minimum interval
between two task runs
- max_interval (datetime.timedelta): the maximum interval
between two task runs
- backoff_factor (float): the factor by which the interval
changes at each run
- max_queue_length (int): the maximum length of the task queue
for this task type
"""
query = self._format_query(
"""insert into task_type ({keys}) values ({placeholders})""",
self.task_type_keys,
)
cursor.execute(query, [task_type[key] for key in self.task_type_keys])
@autocommit
def get_task_type(self, task_type_name, cursor=None):
"""Retrieve the task type with id task_type_name"""
query = self._format_query(
"select {keys} from task_type where type=%s",
self.task_type_keys,
)
cursor.execute(query, (task_type_name,))
ret = cursor.fetchone()
return ret
@autocommit
def get_task_types(self, cursor=None):
query = self._format_query(
"select {keys} from task_type",
self.task_type_keys,
)
cursor.execute(query)
ret = cursor.fetchall()
return ret
task_create_keys = [
'type', 'arguments', 'next_run', 'policy', 'retries_left',
]
task_keys = task_create_keys + ['id', 'current_interval', 'status']
@autocommit
def create_tasks(self, tasks, cursor=None):
"""Create new tasks.
Args:
tasks (list): each task is a dictionary with the following keys:
- type (str): the task type
- arguments (dict): the arguments for the task runner, keys:
- args (list of str): arguments
- kwargs (dict str -> str): keyword arguments
- next_run (datetime.datetime): the next scheduled run for the
task
Returns:
a list of created tasks.
"""
cursor.execute('select swh_scheduler_mktemp_task()')
self.copy_to(tasks, 'tmp_task', self.task_create_keys, cursor)
query = self._format_query(
'select {keys} from swh_scheduler_create_tasks_from_temp()',
self.task_keys,
)
cursor.execute(query)
return cursor.fetchall()
@autocommit
def disable_tasks(self, task_ids, cursor=None):
"""Disable the tasks whose ids are listed."""
query = "UPDATE task SET status = 'disabled' WHERE id IN %s"
cursor.execute(query, (tuple(task_ids),))
return None
@autocommit
def get_tasks(self, task_ids, cursor=None):
"""Retrieve the info of tasks whose ids are listed."""
query = self._format_query('select {keys} from task where id in %s',
self.task_keys)
cursor.execute(query, (tuple(task_ids),))
return cursor.fetchall()
@autocommit
def peek_ready_tasks(self, task_type, timestamp=None, num_tasks=None,
cursor=None):
"""Fetch the list of ready tasks
Args:
task_type (str): filtering task per their type
timestamp (datetime.datetime): peek tasks that need to be executed
before that timestamp
num_tasks (int): only peek at num_tasks tasks
Returns:
a list of tasks
"""
if timestamp is None:
timestamp = utcnow()
cursor.execute(
'select * from swh_scheduler_peek_ready_tasks(%s, %s, %s)',
(task_type, timestamp, num_tasks)
)
return cursor.fetchall()
@autocommit
def grab_ready_tasks(self, task_type, timestamp=None, num_tasks=None,
cursor=None):
"""Fetch the list of ready tasks, and mark them as scheduled
Args:
task_type (str): filtering task per their type
timestamp (datetime.datetime): grab tasks that need to be executed
before that timestamp
num_tasks (int): only grab num_tasks tasks
Returns:
a list of tasks
"""
if timestamp is None:
timestamp = utcnow()
cursor.execute(
'select * from swh_scheduler_grab_ready_tasks(%s, %s, %s)',
(task_type, timestamp, num_tasks)
)
return cursor.fetchall()
task_run_create_keys = ['task', 'backend_id', 'scheduled', 'metadata']
@autocommit
def schedule_task_run(self, task_id, backend_id, metadata=None,
timestamp=None, cursor=None):
"""Mark a given task as scheduled, adding a task_run entry in the database.
Args:
task_id (int): the identifier for the task being scheduled
backend_id (str): the identifier of the job in the backend
metadata (dict): metadata to add to the task_run entry
timestamp (datetime.datetime): the instant the event occurred
Returns:
a fresh task_run entry
"""
if metadata is None:
metadata = {}
if timestamp is None:
timestamp = utcnow()
cursor.execute(
'select * from swh_scheduler_schedule_task_run(%s, %s, %s, %s)',
(task_id, backend_id, metadata, timestamp)
)
return cursor.fetchone()
@autocommit
def mass_schedule_task_runs(self, task_runs, cursor=None):
"""Schedule a bunch of task runs.
Args:
task_runs (list): a list of dicts with keys:
- task (int): the identifier for the task being scheduled
- backend_id (str): the identifier of the job in the backend
- metadata (dict): metadata to add to the task_run entry
- scheduled (datetime.datetime): the instant the event occurred
Returns:
None
"""
cursor.execute('select swh_scheduler_mktemp_task_run()')
self.copy_to(task_runs, 'tmp_task_run', self.task_run_create_keys,
cursor)
cursor.execute('select swh_scheduler_schedule_task_run_from_temp()')
@autocommit
def start_task_run(self, backend_id, metadata=None, timestamp=None,
cursor=None):
"""Mark a given task as started, updating the corresponding task_run
entry in the database.
Args:
backend_id (str): the identifier of the job in the backend
metadata (dict): metadata to add to the task_run entry
timestamp (datetime.datetime): the instant the event occurred
Returns:
the updated task_run entry
"""
if metadata is None:
metadata = {}
if timestamp is None:
timestamp = utcnow()
cursor.execute(
'select * from swh_scheduler_start_task_run(%s, %s, %s)',
(backend_id, metadata, timestamp)
)
return cursor.fetchone()
@autocommit
def end_task_run(self, backend_id, status, metadata=None, timestamp=None,
result=None, cursor=None):
"""Mark a given task as ended, updating the corresponding task_run entry in the
database.
Args:
backend_id (str): the identifier of the job in the backend
status (str): how the task ended; one of: 'eventful', 'uneventful',
'failed'
metadata (dict): metadata to add to the task_run entry
timestamp (datetime.datetime): the instant the event occurred
Returns:
the updated task_run entry
"""
if metadata is None:
metadata = {}
if timestamp is None:
timestamp = utcnow()
cursor.execute(
'select * from swh_scheduler_end_task_run(%s, %s, %s, %s)',
(backend_id, status, metadata, timestamp)
)
return cursor.fetchone()
@autocommit
def filter_task_to_archive(self, timestamp, limit=10, last_id=-1,
cursor=None):
"""Returns the list of task/task_run prior to a given date to archive.
"""
last_task_run_id = None
while True:
row = None
cursor.execute(
"select * from swh_scheduler_task_to_archive(%s, %s, %s)",
(timestamp, last_id, limit)
)
for row in cursor:
# nested type index does not accept bare values
# transform it as a dict to comply with this
row['arguments']['args'] = {
i: v for i, v in enumerate(row['arguments']['args'])
}
yield row
if not row:
break
_id = row.get('task_id')
_task_run_id = row.get('task_run_id')
if last_id == _id and last_task_run_id == _task_run_id:
break
last_id = _id
last_task_run_id = _task_run_id
@autocommit
def delete_archive_tasks(self, task_ids, cursor=None):
cursor.execute("select * from swh_scheduler_delete_archive_tasks(%s)",
(task_ids, ))

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