Remove stale tasks from task conflict count during task claiming (ela…

…stic#198416)

In this PR, I'm removing the count of stale tasks from the number of
conflicts during the claiming cycle. I am also adding a new property to
the task manager health report (`claim_stale_tasks`) so we can track
those separately to ensure we have the proper page size.

## To verify
Apply the following diff, observe the new `claim_stale_tasks` in the TM
health API and that conflicts are 0
```
diff --git a/x-pack/plugins/task_manager/server/task_claimers/strategy_mget.ts b/x-pack/plugins/task_manager/server/task_claimers/strategy_mget.ts
index 4e74454e8c9..35d7fd872d8 100644
--- a/x-pack/plugins/task_manager/server/task_claimers/strategy_mget.ts
+++ b/x-pack/plugins/task_manager/server/task_claimers/strategy_mget.ts
@@ -145,6 +145,7 @@ async function claimAvailableTasks(opts: TaskClaimerOpts): Promise<ClaimOwnershi
     }

     if (
+      false &&
       searchVersion.seqNo === latestVersion.seqNo &&
       searchVersion.primaryTerm === latestVersion.primaryTerm
     ) {
```

(cherry picked from commit 37ebf29)

x-pack/plugins/task_manager/server/monitoring/task_run_statistics.ts

@@ -45,6 +45,7 @@ interface FillPoolStat extends JsonObject {
   claim_duration: number[];
   claim_conflicts: number[];
   claim_mismatches: number[];
+  claim_stale_tasks: number[];
   result_frequency_percent_as_number: FillPoolResult[];
   persistence: TaskPersistence[];
 }
@@ -150,6 +151,7 @@ export function createTaskRunAggregator(
   const claimDurationQueue = createRunningAveragedStat<number>(runningAverageWindowSize);
   const claimConflictsQueue = createRunningAveragedStat<number>(runningAverageWindowSize);
   const claimMismatchesQueue = createRunningAveragedStat<number>(runningAverageWindowSize);
+  const claimStaleTasksQueue = createRunningAveragedStat<number>(runningAverageWindowSize);
   const polledTasksByPersistenceQueue =
     createRunningAveragedStat<TaskPersistence>(runningAverageWindowSize);
   const taskPollingEvents$: Observable<Pick<TaskRunStat, 'polling'>> = combineLatest([
@@ -161,9 +163,8 @@ export function createTaskRunAggregator(
           isOk<ClaimAndFillPoolResult, unknown>(taskEvent.event)
       ),
       map((taskEvent: TaskLifecycleEvent) => {
-        const { result, stats: { tasksClaimed, tasksUpdated, tasksConflicted } = {} } = (
-          taskEvent.event as unknown as Ok<ClaimAndFillPoolResult>
-        ).value;
+        const { result, stats: { tasksClaimed, tasksUpdated, tasksConflicted, staleTasks } = {} } =
+          (taskEvent.event as unknown as Ok<ClaimAndFillPoolResult>).value;
         const duration = (taskEvent?.timing?.stop ?? 0) - (taskEvent?.timing?.start ?? 0);
         return {
           polling: {
@@ -179,6 +180,9 @@ export function createTaskRunAggregator(
               isNumber(tasksClaimed) && isNumber(tasksUpdated)
                 ? claimMismatchesQueue(tasksUpdated - tasksClaimed)
                 : claimMismatchesQueue(),
+            claim_stale_tasks: isNumber(staleTasks)
+              ? claimStaleTasksQueue(staleTasks)
+              : claimStaleTasksQueue(),
             result_frequency_percent_as_number: resultFrequencyQueue(result),
           },
         };
@@ -258,6 +262,7 @@ export function createTaskRunAggregator(
           claim_duration: [],
           claim_conflicts: [],
           claim_mismatches: [],
+          claim_stale_tasks: [],
           result_frequency_percent_as_number: [],
           persistence: [],
         },
@@ -347,6 +352,7 @@ export function summarizeTaskRunStat(
       result_frequency_percent_as_number: pollingResultFrequency,
       claim_conflicts: claimConflicts,
       claim_mismatches: claimMismatches,
+      claim_stale_tasks: claimStaleTasks,
       persistence: pollingPersistence,
     },
     drift,
@@ -373,6 +379,7 @@ export function summarizeTaskRunStat(
         duration: calculateRunningAverage(pollingDuration as number[]),
         claim_conflicts: calculateRunningAverage(claimConflicts as number[]),
         claim_mismatches: calculateRunningAverage(claimMismatches as number[]),
+        claim_stale_tasks: calculateRunningAverage(claimStaleTasks as number[]),
         result_frequency_percent_as_number: {
           ...DEFAULT_POLLING_FREQUENCIES,
           ...calculateFrequency<FillPoolResult>(pollingResultFrequency as FillPoolResult[]),

x-pack/plugins/task_manager/server/routes/health.test.ts

@@ -942,6 +942,7 @@ function mockHealthStats(overrides = {}) {
             claim_conflicts: [0, 100, 75],
             claim_mismatches: [0, 100, 75],
             claim_duration: [0, 100, 75],
+            claim_stale_tasks: [0, 100, 75],
             result_frequency_percent_as_number: [
               FillPoolResult.NoTasksClaimed,
               FillPoolResult.NoTasksClaimed,

x-pack/plugins/task_manager/server/task_claimers/index.ts

@@ -40,6 +40,7 @@ export interface ClaimOwnershipResult {
     tasksClaimed: number;
     tasksLeftUnclaimed?: number;
     tasksErrors?: number;
+    staleTasks?: number;
   };
   docs: ConcreteTaskInstance[];
   timing?: TaskTiming;
@@ -70,6 +71,7 @@ export function getEmptyClaimOwnershipResult(): ClaimOwnershipResult {
       tasksUpdated: 0,
       tasksConflicted: 0,
       tasksClaimed: 0,
+      staleTasks: 0,
     },
     docs: [],
   };

x-pack/plugins/task_manager/server/task_claimers/strategy_mget.test.ts

@@ -433,6 +433,7 @@ describe('TaskClaiming', () => {
         tasksConflicted: 0,
         tasksErrors: 0,
         tasksUpdated: 3,
+        staleTasks: 0,
         tasksLeftUnclaimed: 3,
       });
       expect(result.docs.length).toEqual(3);
@@ -529,6 +530,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 1,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(1);
     });
@@ -640,6 +642,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 1,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(1);
     });
@@ -737,6 +740,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 1,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(1);
     });
@@ -792,6 +796,7 @@ describe('TaskClaiming', () => {
         tasksClaimed: 0,
         tasksConflicted: 0,
         tasksUpdated: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(0);
     });
@@ -885,6 +890,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 2,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(2);
     });
@@ -978,6 +984,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 2,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(2);
     });
@@ -1031,7 +1038,7 @@ describe('TaskClaiming', () => {
       expect(mockApmTrans.end).toHaveBeenCalledWith('success');
 
       expect(taskManagerLogger.debug).toHaveBeenCalledWith(
-        'task claimer claimed: 2; stale: 1; conflicts: 1; missing: 0; capacity reached: 0; updateErrors: 0; getErrors: 0; removed: 0;',
+        'task claimer claimed: 2; stale: 1; conflicts: 0; missing: 0; capacity reached: 0; updateErrors: 0; getErrors: 0; removed: 0;',
         { tags: ['taskClaiming', 'claimAvailableTasksMget'] }
       );
 
@@ -1067,10 +1074,11 @@ describe('TaskClaiming', () => {
 
       expect(result.stats).toEqual({
         tasksClaimed: 2,
-        tasksConflicted: 1,
+        tasksConflicted: 0,
         tasksErrors: 0,
         tasksUpdated: 2,
         tasksLeftUnclaimed: 0,
+        staleTasks: 1,
       });
       expect(result.docs.length).toEqual(2);
     });
@@ -1197,6 +1205,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 4,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(4);
     });
@@ -1330,6 +1339,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 1,
         tasksUpdated: 3,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(3);
     });
@@ -1458,6 +1468,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 4,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(4);
       for (const r of result.docs) {
@@ -1699,6 +1710,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 1,
         tasksUpdated: 3,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(3);
     });
@@ -1829,6 +1841,7 @@ describe('TaskClaiming', () => {
         tasksErrors: 0,
         tasksUpdated: 3,
         tasksLeftUnclaimed: 0,
+        staleTasks: 0,
       });
       expect(result.docs.length).toEqual(3);
     });

x-pack/plugins/task_manager/server/task_claimers/strategy_mget.ts

@@ -196,7 +196,7 @@ async function claimAvailableTasks(opts: TaskClaimerOpts): Promise<ClaimOwnershi
 
   // perform the task object updates, deal with errors
   const updatedTaskIds: string[] = [];
-  let conflicts = staleTasks.length;
+  let conflicts = 0;
   let bulkUpdateErrors = 0;
   let bulkGetErrors = 0;
 
@@ -288,6 +288,7 @@ async function claimAvailableTasks(opts: TaskClaimerOpts): Promise<ClaimOwnershi
       tasksClaimed: fullTasksToRun.length,
       tasksLeftUnclaimed: leftOverTasks.length,
       tasksErrors: bulkUpdateErrors + bulkGetErrors,
+      staleTasks: staleTasks.length,
     },
     docs: fullTasksToRun,
     timing: stopTaskTimer(),