chore: replace GetManagedAgentCount query with aggregate table (#19636)

- Removes GetManagedAgentCount query
- Adds new table `usage_events_daily` which stores aggregated usage
events by the type and UTC day
- Adds trigger to update the values in this table when a new row is
inserted into `usage_events`
- Adds a migration that adds `usage_events_daily` rows for existing data
in `usage_events`
- Adds tests for the trigger
- Adds tests for the backfill query in the migration

Since the `usage_events` table is unreleased currently, this migration
will do nothing on real deployments and will only affect preview
deployments such as dogfood.

Closes https://github.com/coder/internal/issues/943

enterprise/coderd/coderd.go

@@ -984,10 +984,10 @@ func (api *API) CheckBuildUsage(ctx context.Context, store database.Store, templ
 
 		// This check is intentionally not committed to the database. It's fine if
 		// it's not 100% accurate or allows for minor breaches due to build races.
-		// nolint:gocritic // Requires permission to read all workspaces to read managed agent count.
-		managedAgentCount, err := store.GetManagedAgentCount(agpldbauthz.AsSystemRestricted(ctx), database.GetManagedAgentCountParams{
-			StartTime: managedAgentLimit.UsagePeriod.Start,
-			EndTime:   managedAgentLimit.UsagePeriod.End,
+		// nolint:gocritic // Requires permission to read all usage events.
+		managedAgentCount, err := store.GetTotalUsageDCManagedAgentsV1(agpldbauthz.AsSystemRestricted(ctx), database.GetTotalUsageDCManagedAgentsV1Params{
+			StartDate: managedAgentLimit.UsagePeriod.Start,
+			EndDate:   managedAgentLimit.UsagePeriod.End,
 		})
 		if err != nil {
 			return wsbuilder.UsageCheckResponse{}, xerrors.Errorf("get managed agent count: %w", err)

enterprise/coderd/license/license.go

@@ -125,10 +125,19 @@ func Entitlements(
 		ExternalWorkspaceCount: int64(len(externalWorkspaces)),
 		ExternalTemplateCount:  int64(len(externalTemplates)),
 		ManagedAgentCountFn: func(ctx context.Context, startTime time.Time, endTime time.Time) (int64, error) {
+			// This is not super accurate, as the start and end times will be
+			// truncated to the date in UTC timezone. This is an optimization
+			// so we can use an aggregate table instead of scanning the usage
+			// events table.
+			//
+			// High accuracy is not super necessary, as we give buffers in our
+			// licenses (e.g. higher hard limit) to account for additional
+			// usage.
+			//
 			// nolint:gocritic // Requires permission to read all workspaces to read managed agent count.
-			return db.GetManagedAgentCount(dbauthz.AsSystemRestricted(ctx), database.GetManagedAgentCountParams{
-				StartTime: startTime,
-				EndTime:   endTime,
+			return db.GetTotalUsageDCManagedAgentsV1(dbauthz.AsSystemRestricted(ctx), database.GetTotalUsageDCManagedAgentsV1Params{
+				StartDate: startTime,
+				EndDate:   endTime,
 			})
 		},
 	})

enterprise/coderd/license/license_test.go

@@ -827,12 +827,17 @@ func TestEntitlements(t *testing.T) {
 			GetActiveUserCount(gomock.Any(), false).
 			Return(int64(1), nil)
 		mDB.EXPECT().
-			GetManagedAgentCount(gomock.Any(), gomock.Cond(func(params database.GetManagedAgentCountParams) bool {
-				// gomock doesn't seem to compare times very nicely.
-				if !assert.WithinDuration(t, licenseOpts.NotBefore, params.StartTime, time.Second) {
+			GetTotalUsageDCManagedAgentsV1(gomock.Any(), gomock.Cond(func(params database.GetTotalUsageDCManagedAgentsV1Params) bool {
+				// gomock doesn't seem to compare times very nicely, so check
+				// them manually.
+				//
+				// The query truncates these times to the date in UTC timezone,
+				// but we still check that we're passing in the correct
+				// timestamp in the first place.
+				if !assert.WithinDuration(t, licenseOpts.NotBefore, params.StartDate, time.Second) {
 					return false
 				}
-				if !assert.WithinDuration(t, licenseOpts.ExpiresAt, params.EndTime, time.Second) {
+				if !assert.WithinDuration(t, licenseOpts.ExpiresAt, params.EndDate, time.Second) {
 					return false
 				}
 				return true