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Pull out PostgresEventWatcher into its own module and parameterize it…
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python_modules/libraries/dagster-postgres/dagster_postgres/event_log/__init__.py
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1 +1,2 @@ | ||
| from .event_log import PostgresEventLogStorage | ||
| from .event_watcher import PostgresEventWatcher |
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python_modules/libraries/dagster-postgres/dagster_postgres/event_log/event_watcher.py
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,131 @@ | ||
| import logging | ||
| import threading | ||
| from collections import defaultdict | ||
| from typing import Callable, List, MutableMapping, Optional | ||
|
|
||
| from dagster import check | ||
| from dagster.core.events.log import EventLogEntry | ||
| from dagster.core.storage.event_log.polling_event_watcher import CallbackAfterCursor | ||
|
|
||
| from ..pynotify import await_pg_notifications | ||
|
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| POLLING_CADENCE = 0.25 | ||
|
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|
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| def watcher_thread( | ||
| conn_string: str, | ||
| handlers_dict: MutableMapping[str, List[CallbackAfterCursor]], | ||
| dict_lock: threading.Lock, | ||
| watcher_thread_exit: threading.Event, | ||
| watcher_thread_started: threading.Event, | ||
| channels: List[str], | ||
| gen_event_log_entry_from_cursor: Callable[[int], EventLogEntry], | ||
| ): | ||
| for notif in await_pg_notifications( | ||
| conn_string, | ||
| channels=channels, | ||
| timeout=POLLING_CADENCE, | ||
| yield_on_timeout=True, | ||
| exit_event=watcher_thread_exit, | ||
| started_event=watcher_thread_started, | ||
| ): | ||
| if notif is None: | ||
| if watcher_thread_exit.is_set(): | ||
| break | ||
| else: | ||
| run_id, index_str = notif.payload.split("_") | ||
| with dict_lock: | ||
| if run_id not in handlers_dict: | ||
| continue | ||
|
|
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| index = int(index_str) | ||
| with dict_lock: | ||
| handlers = handlers_dict.get(run_id, []) | ||
|
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| dagster_event = gen_event_log_entry_from_cursor(index) | ||
|
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| for callback_with_cursor in handlers: | ||
| if callback_with_cursor.start_cursor < index: | ||
| try: | ||
| callback_with_cursor.callback(dagster_event) | ||
| except Exception: | ||
| logging.exception( | ||
| "Exception in callback for event watch on run %s.", run_id | ||
| ) | ||
|
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|
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| class PostgresEventWatcher: | ||
| def __init__( | ||
| self, | ||
| conn_string: str, | ||
| channels: List[str], | ||
| gen_event_log_entry_from_cursor: Callable[[int], EventLogEntry], | ||
| ): | ||
| self._conn_string: str = check.str_param(conn_string, "conn_string") | ||
| self._handlers_dict: MutableMapping[str, List[CallbackAfterCursor]] = defaultdict(list) | ||
| self._dict_lock: threading.Lock = threading.Lock() | ||
| self._watcher_thread_exit: Optional[threading.Event] = None | ||
| self._watcher_thread_started: Optional[threading.Event] = None | ||
| self._watcher_thread: Optional[threading.Thread] = None | ||
| self._channels: List[str] = check.list_param(channels, "channels") | ||
| self._gen_event_log_entry_from_cursor: Callable[ | ||
| [int], EventLogEntry | ||
| ] = check.callable_param(gen_event_log_entry_from_cursor, "gen_event_log_entry_from_cursor") | ||
|
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| def watch_run( | ||
| self, | ||
| run_id: str, | ||
| start_cursor: int, | ||
| callback: Callable[[EventLogEntry], None], | ||
| start_timeout=15, | ||
| ): | ||
| check.str_param(run_id, "run_id") | ||
| check.int_param(start_cursor, "start_cursor") | ||
| check.callable_param(callback, "callback") | ||
| if not self._watcher_thread: | ||
| self._watcher_thread_exit = threading.Event() | ||
| self._watcher_thread_started = threading.Event() | ||
|
|
||
| self._watcher_thread = threading.Thread( | ||
| target=watcher_thread, | ||
| args=( | ||
| self._conn_string, | ||
| self._handlers_dict, | ||
| self._dict_lock, | ||
| self._watcher_thread_exit, | ||
| self._watcher_thread_started, | ||
| self._channels, | ||
| self._gen_event_log_entry_from_cursor, | ||
| ), | ||
| name="postgres-event-watch", | ||
| ) | ||
| self._watcher_thread.daemon = True | ||
| self._watcher_thread.start() | ||
|
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||
| # Wait until the watcher thread is actually listening before returning | ||
| self._watcher_thread_started.wait(start_timeout) | ||
| if not self._watcher_thread_started.is_set(): | ||
| raise Exception("Watcher thread never started") | ||
|
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| with self._dict_lock: | ||
| self._handlers_dict[run_id].append(CallbackAfterCursor(start_cursor + 1, callback)) | ||
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| def unwatch_run(self, run_id: str, handler: Callable[[EventLogEntry], None]): | ||
| check.str_param(run_id, "run_id") | ||
| check.callable_param(handler, "handler") | ||
| with self._dict_lock: | ||
| if run_id in self._handlers_dict: | ||
| self._handlers_dict[run_id] = [ | ||
| callback_with_cursor | ||
| for callback_with_cursor in self._handlers_dict[run_id] | ||
| if callback_with_cursor.callback != handler | ||
| ] | ||
| if not self._handlers_dict[run_id]: | ||
| del self._handlers_dict[run_id] | ||
|
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| def close(self): | ||
| if self._watcher_thread: | ||
| self._watcher_thread_exit.set() | ||
| self._watcher_thread.join() | ||
| self._watcher_thread_exit = None | ||
| self._watcher_thread = None |