Allow manual IANA-compliant specification of DB timezone

Author: woodlee

k8s-deploy.yml

@@ -6,6 +6,7 @@
 import time
 from datetime import datetime, timedelta
 from typing import Dict, Any
+from zoneinfo import ZoneInfo
 
 from . import config, queries, message_schemas, common
 
@@ -20,6 +21,10 @@ def poll_db(db_identifier: str, odbc_conn_string: str, stop_event: mp.Event,
 
     try:
         conn, db_tz = common.get_db_conn_with_failover(odbc_conn_string)
+        if config.DB_TIMEZONE:
+            db_tz = ZoneInfo(config.DB_TIMEZONE)
+            logger.info('Ignoring TZ offset queried from DB to use IANA TZ "%s" specified in config',
+                        config.DB_TIMEZONE)
         next_poll_due = datetime.utcnow()
         read_executions_from = (datetime.now(db_tz) -
                                 timedelta(minutes=config.REFRESH_INTERVAL_MINUTES)).replace(tzinfo=None)

plan_monitor/collect.py

@@ -18,6 +18,12 @@
 ODBC_CONN_STRINGS = json.loads(os.environ.get('ODBC_CONN_STRINGS', '''
 {"LOCAL": "DRIVER=FreeTDS; Server=localhost; Database=MyDB; UID=sa; PWD=1Password; Port=1433; App=plan_monitor;"}'''))
 
+# Allows specifying an IANA timezone name which will be used to interpret all timestamps returned by the DB queries
+# this tool makes. Note that this value will be used for ALL DBs specified in ODBC_CONN_STRINGS. If left unspecified,
+# each DB will instead be queried for its current numeric UTC offset at process start, and that will be used instead.
+# Using a numeric offset can be problematic for DBs whose clocks may change (e.g. due to Daylight Savings Time),
+# though, hence this option:
+DB_TIMEZONE = os.environ.get('DB_TIMEZONE')  # IANA-compliant; for example 'America/Los_Angeles'
 
 # Configuration with sane defaults for most deployments but that you can change if you wish:
 # ------------------------------------------------------------------------------------------------------------