[ResponseOps] Adding back recovered alert optimization for the task state (#215344)

## Summary

I refactored the flapping code on ON week in PR
https://github.com/elastic/kibana/pull/213825 , and I removed an
optimization for removing recovered alerts from the task state that we
don't need to track for flapping. This PR adds it back.


### Checklist

- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

### To verify
1. Create an rule let it be active for a little and then let it recover.
2. Verify that once the flapping array doesn't have any `true` values
changes

x-pack/platform/plugins/shared/alerting/server/alerts_client/alerts_client.ts

@@ -345,8 +345,8 @@ export class AlertsClient<
     return await this.updatePersistedAlertsWithMaintenanceWindowIds();
   }
 
-  public getRawAlertInstancesForState() {
-    return this.legacyAlertsClient.getRawAlertInstancesForState();
+  public getRawAlertInstancesForState(shouldOptimizeTaskState?: boolean) {
+    return this.legacyAlertsClient.getRawAlertInstancesForState(shouldOptimizeTaskState);
   }
 
   public factory() {

x-pack/platform/plugins/shared/alerting/server/alerts_client/legacy_alerts_client.ts

@@ -211,10 +211,11 @@ export class LegacyAlertsClient<
     return {};
   }
 
-  public getRawAlertInstancesForState() {
+  public getRawAlertInstancesForState(shouldOptimizeTaskState?: boolean) {
     return toRawAlertInstances<State, Context, ActionGroupIds, RecoveryActionGroupId>(
       this.processedAlerts.trackedActiveAlerts,
-      this.processedAlerts.trackedRecoveredAlerts
+      this.processedAlerts.trackedRecoveredAlerts,
+      shouldOptimizeTaskState
     );
   }
 

x-pack/platform/plugins/shared/alerting/server/alerts_client/types.ts

@@ -85,7 +85,7 @@ export interface IAlertsClient<
   persistAlerts(): Promise<{ alertIds: string[]; maintenanceWindowIds: string[] } | null>;
   isTrackedAlert(id: string): boolean;
   getSummarizedAlerts?(params: GetSummarizedAlertsParams): Promise<SummarizedAlerts>;
-  getRawAlertInstancesForState(): {
+  getRawAlertInstancesForState(shouldOptimizeTaskState?: boolean): {
     rawActiveAlerts: Record<string, RawAlertInstance>;
     rawRecoveredAlerts: Record<string, RawAlertInstance>;
   };

x-pack/platform/plugins/shared/alerting/server/lib/to_raw_alert_instances.test.ts

@@ -31,5 +31,14 @@ describe('toRawAlertInstances', () => {
       const { rawRecoveredAlerts } = toRawAlertInstances({}, recoveredAlerts);
       expect(keys(rawRecoveredAlerts)).toEqual(['1', '2']);
     });
+
+    test('should return all flapping recovered alerts', () => {
+      const recoveredAlerts = {
+        '1': new Alert('1', { meta: { flappingHistory: flapping } }),
+        '2': new Alert('2', { meta: { flappingHistory: notFlapping } }),
+      };
+      const { rawRecoveredAlerts } = toRawAlertInstances({}, recoveredAlerts, true);
+      expect(keys(rawRecoveredAlerts)).toEqual(['1']);
+    });
   });
 });

x-pack/platform/plugins/shared/alerting/server/lib/to_raw_alert_instances.ts

@@ -16,7 +16,8 @@ export function toRawAlertInstances<
   RecoveryActionGroupId extends string
 >(
   activeAlerts: Record<string, Alert<State, Context, ActionGroupIds>> = {},
-  recoveredAlerts: Record<string, Alert<State, Context, RecoveryActionGroupId>> = {}
+  recoveredAlerts: Record<string, Alert<State, Context, RecoveryActionGroupId>> = {},
+  shouldOptimizeTaskState: boolean = false
 ): {
   rawActiveAlerts: Record<string, RawAlertInstance>;
   rawRecoveredAlerts: Record<string, RawAlertInstance>;
@@ -30,7 +31,20 @@ export function toRawAlertInstances<
 
   for (const id of keys(recoveredAlerts)) {
     const alert = recoveredAlerts[id];
-    rawRecoveredAlerts[id] = alert.toRaw(true);
+    if (shouldOptimizeTaskState) {
+      // this is a space saving effort that will only return recovered alerts if they are flapping
+      // or if the flapping array contains any state changes
+      const flapping = alert.getFlapping();
+      const flappingHistory: boolean[] = alert.getFlappingHistory() || [];
+      const numStateChanges = flappingHistory.filter((f) => f).length;
+      if (flapping) {
+        rawRecoveredAlerts[id] = alert.toRaw(true);
+      } else if (numStateChanges > 0) {
+        rawRecoveredAlerts[id] = alert.toRaw(true);
+      }
+    } else {
+      rawRecoveredAlerts[id] = alert.toRaw(true);
+    }
   }
   return { rawActiveAlerts, rawRecoveredAlerts };
 }

x-pack/platform/plugins/shared/alerting/server/task_runner/task_runner.ts

@@ -432,7 +432,7 @@ export class TaskRunner<
     // Only serialize alerts into task state if we're auto-recovering, otherwise
     // we don't need to keep this information around.
     if (this.ruleType.autoRecoverAlerts) {
-      const alerts = alertsClient.getRawAlertInstancesForState();
+      const alerts = alertsClient.getRawAlertInstancesForState(true);
       alertsToReturn = alerts.rawActiveAlerts;
       recoveredAlertsToReturn = alerts.rawRecoveredAlerts;
     }