mypy: pglookout/pglookout.py [BF-1560]

pglookout/cluster_monitor.py

@@ -15,7 +15,7 @@
 from logging.handlers import SysLogHandler
 from pglookout import logutil
 from pglookout.common import get_iso_timestamp, parse_iso_datetime
-from pglookout.common_types import MemberState, ObserverState, ReplicationSlotAsDict
+from pglookout.common_types import MemberState, ObservedState, ReplicationSlotAsDict
 from pglookout.config import Config
 from pglookout.pgutil import mask_connection_info
 from pglookout.statsd import StatsClient
@@ -78,7 +78,7 @@ def __init__(
         self,
         config: Config,
         cluster_state: dict[str, MemberState],
-        observer_state: dict[str, ObserverState],
+        observer_state: dict[str, ObservedState],
         create_alert_file: Callable[[str], None],
         cluster_monitor_check_queue: Queue[str],
         failover_decision_queue: Queue[str],
@@ -96,7 +96,7 @@ def __init__(
         self.stats: StatsClient = stats
         self.running: bool = True
         self.cluster_state: dict[str, MemberState] = cluster_state
-        self.observer_state: dict[str, ObserverState] = observer_state
+        self.observer_state: dict[str, ObservedState] = observer_state
         self.config: Config = config
         self.create_alert_file: Callable[[str], None] = create_alert_file
         self.db_conns: dict[str, psycopg2.connection | None] = {}
@@ -152,7 +152,7 @@ def _connect_to_db(self, instance: str, dsn: str | None) -> psycopg2.connection
         self.db_conns[instance] = conn
         return conn
 
-    def _fetch_observer_state(self, instance: str, uri: str) -> ObserverState | None:
+    def _fetch_observer_state(self, instance: str, uri: str) -> ObservedState | None:
         now_iso = get_iso_timestamp()
         result = {"fetch_time": now_iso, "connection": True}
         fetch_uri = uri + "/state.json"
@@ -194,7 +194,7 @@ def _fetch_observer_state(self, instance: str, uri: str) -> ObserverState | None
             self.stats.unexpected_exception(ex, where="_fetch_observer_state")
             result["connection"] = False
 
-        return result
+        return cast(ObservedState, result)
 
     def fetch_observer_state(self, instance: str, uri: str) -> None:
         start_time = time.monotonic()

pglookout/common_types.py

@@ -2,7 +2,7 @@
 from __future__ import annotations
 
 from datetime import datetime
-from typing import Any, Dict, TypedDict
+from typing import TypedDict, Union
 
 
 class ReplicationSlotAsDict(TypedDict, total=True):
@@ -44,10 +44,27 @@ class MemberState(TypedDict, total=False):
 
 
 # Note for future improvements:
-# If we want ObserverState to accept arbitrary keys, we have three choices:
+# If we want ObservedState to accept arbitrary keys, we have three choices:
 # - Use a different type (pydantic, dataclasses, etc.)
 # - Use a TypedDict for static keys (connection, fetch_time) and a sub-dict for
 #   dynamic keys (received from state.json).
 # - Wait for something like `allow_extra` to be implemented into TypedDict (unlikely)
 #   https://github.com/python/mypy/issues/4617
-ObserverState = Dict[str, Any]
+class ObservedState(dict[str, Union[MemberState, bool, str]]):
+    """Represents an observed state, from the perspective of an observer.
+
+    Note:
+        The content of this type is dynamic, as it depends on the number of
+        members in the cluster. There are two static keys, connection and
+        fetch_time, and N dynamic keys, one for each member of the cluster.
+        Like so::
+
+            connection: bool
+            fetch_time: str
+            name_or_ip_1: MemberState
+            name_or_ip_2: MemberState
+            ...
+            name_or_ip_N: MemberState
+    """
+
+    pass

pglookout/current_master.py

@@ -11,6 +11,7 @@
 from __future__ import annotations
 
 from . import version
+from pglookout.default import JSON_STATE_FILE_PATH
 
 import argparse
 import json
@@ -43,7 +44,7 @@ def main(args: list[str] | None = None) -> int:
     try:
         with open(arg.state, "r") as fp:
             config = json.load(fp)
-        state_file_path = config.get("json_state_file_path", "/tmp/pglookout_state.json")  # pylint: disable=no-member
+        state_file_path = config.get("json_state_file_path", JSON_STATE_FILE_PATH)  # pylint: disable=no-member
         if time.monotonic() - os.stat(state_file_path).st_mtime > 60.0:
             # file older than one minute, pglookout probably dead, exit with minus one
             return -1

pglookout/default.py

@@ -0,0 +1,10 @@
+# Copyright (c) 2023 Aiven, Helsinki, Finland. https://aiven.io/
+from typing import Final
+
+WARNING_REPLICATION_TIME_LAG: Final[float] = 30.0
+MAX_FAILOVER_REPLICATION_TIME_LAG: Final[float] = 120.0
+REPLICATION_CATCHUP_TIMEOUT: Final[float] = 300.0
+MISSING_MASTER_FROM_CONFIG_TIMEOUT: Final[float] = 15.0
+MAINTENANCE_MODE_FILE: Final[str] = "/tmp/pglookout_maintenance_mode_file"
+PG_DATA_DIRECTORY: Final[str] = "/var/lib/pgsql/data"
+JSON_STATE_FILE_PATH: Final[str] = "/tmp/pglookout_state.json"