ref(crons): Add migration to backfill MonitorEnvironment.is_muted

Implements Step 2 of the migration plan from [NEW-564: There needs to be some way to mute the entire cron detector](https://linear.app/getsentry/issue/NEW-564/there-needs-to-be-some-way-to-mute-the-entire-cron-detector)

This data migration backfills MonitorEnvironment.is_muted from Monitor.is_muted for all muted monitors. This ensures existing data is consistent before switching to read from MonitorEnvironment.is_muted.

After this migration runs:
- Monitors with is_muted=True will have ALL environments muted
- Monitors with is_muted=False will have environments unchanged

This establishes the correct invariant:
- Monitor is muted ↔ ALL environments are muted
- Monitor is unmuted ↔ ANY environment is unmuted

The migration:
- Uses range queries for efficient batching (1000 monitors per batch)
- Only updates environments for muted monitors (unmuted is the default)
- Is marked as post-deployment for manual execution in production

Test verifies:
- Muted monitor environments are updated to is_muted=True
- Unmuted monitor environments remain unchanged
- Monitors without environments are unaffected

Author: evanpurkhiser

migrations_lockfile.txt

@@ -17,7 +17,7 @@ hybridcloud: 0024_add_project_distribution_scope
 
 insights: 0002_backfill_team_starred
 
-monitors: 0010_delete_orphaned_detectors
+monitors: 0011_backfill_monitor_environment_is_muted
 
 nodestore: 0001_squashed_0002_nodestore_no_dictfield
 

src/sentry/monitors/migrations/0011_backfill_monitor_environment_is_muted.py

@@ -0,0 +1,60 @@
+# Generated by Django 5.2.1 on 2025-11-13 19:27
+
+from django.db import migrations
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.migrations.state import StateApps
+
+from sentry.new_migrations.migrations import CheckedMigration
+from sentry.utils.query import RangeQuerySetWrapperWithProgressBar
+
+
+def backfill_monitor_environment_is_muted(
+    apps: StateApps, schema_editor: BaseDatabaseSchemaEditor
+) -> None:
+    """
+    Backfill MonitorEnvironment.is_muted from Monitor.is_muted for all muted monitors.
+
+    After this migration:
+    - is_muted=True monitors will have ALL environments muted
+    - is_muted=False monitors will have environments unchanged (some, none, or all unmuted)
+
+    This gets us into the correct state for the dual-write implementation where:
+    - Monitor is muted if and only if ALL environments are muted
+    - Monitor is unmuted if ANY environment is unmuted
+    """
+    Monitor = apps.get_model("monitors", "Monitor")
+    MonitorEnvironment = apps.get_model("monitors", "MonitorEnvironment")
+
+    # Only need to update environments for muted monitors since unmuted is already the default
+    muted_monitors = Monitor.objects.filter(is_muted=True)
+
+    for monitor in RangeQuerySetWrapperWithProgressBar(muted_monitors):
+        MonitorEnvironment.objects.filter(monitor=monitor).update(is_muted=True)
+
+
+class Migration(CheckedMigration):
+    # This flag is used to mark that a migration shouldn't be automatically run in production.
+    # This should only be used for operations where it's safe to run the migration after your
+    # code has deployed. So this should not be used for most operations that alter the schema
+    # of a table.
+    # Here are some things that make sense to mark as post deployment:
+    # - Large data migrations. Typically we want these to be run manually so that they can be
+    #   monitored and not block the deploy for a long period of time while they run.
+    # - Adding indexes to large tables. Since this can take a long time, we'd generally prefer to
+    #   run this outside deployments so that we don't block them. Note that while adding an index
+    #   is a schema change, it's completely safe to run the operation after the code has deployed.
+    # Once deployed, run these manually via: https://develop.sentry.dev/database-migrations/#migration-deployment
+
+    is_post_deployment = True
+
+    dependencies = [
+        ("monitors", "0010_delete_orphaned_detectors"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            backfill_monitor_environment_is_muted,
+            migrations.RunPython.noop,
+            hints={"tables": ["monitors_monitor", "monitors_monitorenvironment"]},
+        ),
+    ]

tests/sentry/monitors/migrations/test_0011_backfill_monitor_environment_is_muted.py

@@ -0,0 +1,72 @@
+from sentry.testutils.cases import TestMigrations
+
+
+class BackfillMonitorEnvironmentIsMutedTest(TestMigrations):
+    migrate_from = "0010_delete_orphaned_detectors"
+    migrate_to = "0011_backfill_monitor_environment_is_muted"
+    app = "monitors"
+
+    def setup_initial_state(self) -> None:
+        # Create muted monitor with environments
+        self.muted_monitor = self.create_monitor(name="Muted Monitor", is_muted=True)
+        self.muted_env1 = self.create_monitor_environment(
+            monitor=self.muted_monitor,
+            environment_id=self.environment.id,
+            is_muted=False,  # Initially not muted
+        )
+        env2 = self.create_environment(name="production", project=self.project)
+        self.muted_env2 = self.create_monitor_environment(
+            monitor=self.muted_monitor,
+            environment_id=env2.id,
+            is_muted=False,  # Initially not muted
+        )
+
+        # Create unmuted monitor with environments
+        self.unmuted_monitor = self.create_monitor(name="Unmuted Monitor", is_muted=False)
+        self.unmuted_env1 = self.create_monitor_environment(
+            monitor=self.unmuted_monitor,
+            environment_id=self.environment.id,
+            is_muted=False,
+        )
+        env3 = self.create_environment(name="staging", project=self.project)
+        self.unmuted_env2 = self.create_monitor_environment(
+            monitor=self.unmuted_monitor,
+            environment_id=env3.id,
+            is_muted=False,
+        )
+
+        # Create muted monitor without environments
+        self.muted_monitor_no_envs = self.create_monitor(
+            name="Muted Monitor No Envs", is_muted=True
+        )
+
+        # Verify initial state
+        assert self.muted_monitor.is_muted is True
+        assert self.muted_env1.is_muted is False
+        assert self.muted_env2.is_muted is False
+        assert self.unmuted_monitor.is_muted is False
+        assert self.unmuted_env1.is_muted is False
+        assert self.unmuted_env2.is_muted is False
+
+    def test(self) -> None:
+        # Refresh from DB to get updated state after migration
+        self.muted_monitor.refresh_from_db()
+        self.muted_env1.refresh_from_db()
+        self.muted_env2.refresh_from_db()
+        self.unmuted_monitor.refresh_from_db()
+        self.unmuted_env1.refresh_from_db()
+        self.unmuted_env2.refresh_from_db()
+        self.muted_monitor_no_envs.refresh_from_db()
+
+        # Verify muted monitor has all environments muted
+        assert self.muted_monitor.is_muted is True
+        assert self.muted_env1.is_muted is True
+        assert self.muted_env2.is_muted is True
+
+        # Verify unmuted monitor environments remain unchanged
+        assert self.unmuted_monitor.is_muted is False
+        assert self.unmuted_env1.is_muted is False
+        assert self.unmuted_env2.is_muted is False
+
+        # Verify muted monitor without environments still muted
+        assert self.muted_monitor_no_envs.is_muted is True