refactor: untangle worker eligibility from previous worker node

[poolifier.git] / tests / pools / selection-strategies / selection-strategies.test.js

diff --git a/tests/pools/selection-strategies/selection-strategies.test.js b/tests/pools/selection-strategies/selection-strategies.test.js
index b2aa4a0b69fbd4e006ce6f53fecb90295edb535d..055a2dbb64e6257bef21221f709c2e0756b89d84 100644 (file)
--- a/tests/pools/selection-strategies/selection-strategies.test.js
+++ b/tests/pools/selection-strategies/selection-strategies.test.js
@@ -1,9 +1,10 @@
 const { expect } = require('expect')
 const {
-  WorkerChoiceStrategies,
+  DynamicClusterPool,
   DynamicThreadPool,
+  FixedClusterPool,
   FixedThreadPool,
-  FixedClusterPool
+  WorkerChoiceStrategies
 } = require('../../../lib')
 const { CircularArray } = require('../../../lib/circular-array')
 
@@ -65,6 +66,43 @@ describe('Selection strategies test suite', () => {
       expect(pool.workerChoiceStrategyContext.workerChoiceStrategy).toBe(
         workerChoiceStrategy
       )
+      expect(pool.opts.workerChoiceStrategyOptions).toStrictEqual({
+        retries: 6,
+        runTime: { median: false },
+        waitTime: { median: false },
+        elu: { median: false }
+      })
+      expect(pool.workerChoiceStrategyContext.opts).toStrictEqual({
+        retries: 6,
+        runTime: { median: false },
+        waitTime: { median: false },
+        elu: { median: false }
+      })
+      await pool.destroy()
+    }
+    for (const workerChoiceStrategy of Object.values(WorkerChoiceStrategies)) {
+      const pool = new DynamicClusterPool(
+        min,
+        max,
+        './tests/worker-files/cluster/testWorker.js'
+      )
+      pool.setWorkerChoiceStrategy(workerChoiceStrategy, { retries: 3 })
+      expect(pool.opts.workerChoiceStrategy).toBe(workerChoiceStrategy)
+      expect(pool.workerChoiceStrategyContext.workerChoiceStrategy).toBe(
+        workerChoiceStrategy
+      )
+      expect(pool.opts.workerChoiceStrategyOptions).toStrictEqual({
+        retries: 3,
+        runTime: { median: false },
+        waitTime: { median: false },
+        elu: { median: false }
+      })
+      expect(pool.workerChoiceStrategyContext.opts).toStrictEqual({
+        retries: 3,
+        runTime: { median: false },
+        waitTime: { median: false },
+        elu: { median: false }
+      })
       await pool.destroy()
     }
   })
@@ -75,13 +113,17 @@ describe('Selection strategies test suite', () => {
       './tests/worker-files/thread/testWorker.js'
     )
     for (const workerChoiceStrategy of Object.values(WorkerChoiceStrategies)) {
-      if (workerChoiceStrategy === WorkerChoiceStrategies.ROUND_ROBIN) {
-        expect(
-          pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-            workerChoiceStrategy
-          ).nextWorkerNodeId
-        ).toBe(0)
-      } else if (workerChoiceStrategy === WorkerChoiceStrategies.FAIR_SHARE) {
+      expect(
+        pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+          workerChoiceStrategy
+        ).nextWorkerNodeKey
+      ).toBe(0)
+      expect(
+        pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+          workerChoiceStrategy
+        ).previousWorkerNodeKey
+      ).toBe(0)
+      if (workerChoiceStrategy === WorkerChoiceStrategies.FAIR_SHARE) {
         expect(
           pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
             workerChoiceStrategy
@@ -98,8 +140,17 @@ describe('Selection strategies test suite', () => {
         expect(
           pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
             workerChoiceStrategy
-          ).nextWorkerNodeId
+          ).defaultWorkerWeight
+        ).toBeGreaterThan(0)
+        expect(
+          pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+            workerChoiceStrategy
+          ).workerVirtualTaskRunTime
         ).toBe(0)
+      } else if (
+        workerChoiceStrategy ===
+        WorkerChoiceStrategies.INTERLEAVED_WEIGHTED_ROUND_ROBIN
+      ) {
         expect(
           pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
             workerChoiceStrategy
@@ -110,6 +161,25 @@ describe('Selection strategies test suite', () => {
             workerChoiceStrategy
           ).workerVirtualTaskRunTime
         ).toBe(0)
+        expect(
+          pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+            workerChoiceStrategy
+          ).roundId
+        ).toBe(0)
+        expect(
+          pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+            workerChoiceStrategy
+          ).workerNodeId
+        ).toBe(0)
+        expect(
+          pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+            workerChoiceStrategy
+          ).roundWeights
+        ).toStrictEqual([
+          pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+            workerChoiceStrategy
+          ).defaultWorkerWeight
+        ])
       }
     }
     await pool.destroy()
@@ -123,7 +193,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: true
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -133,7 +204,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: true
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -196,10 +268,11 @@ describe('Selection strategies test suite', () => {
   })
 
   it('Verify ROUND_ROBIN strategy can be run in a fixed pool', async () => {
+    const workerChoiceStrategy = WorkerChoiceStrategies.ROUND_ROBIN
     const pool = new FixedThreadPool(
       max,
       './tests/worker-files/thread/testWorker.js',
-      { workerChoiceStrategy: WorkerChoiceStrategies.ROUND_ROBIN }
+      { workerChoiceStrategy }
     )
     // TODO: Create a better test to cover `RoundRobinWorkerChoiceStrategy#choose`
     const promises = new Set()
@@ -215,52 +288,46 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
         runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        WorkerChoiceStrategies.ROUND_ROBIN
-      ).nextWorkerNodeId
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
     ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toBe(pool.workerNodes.length - 1)
     // We need to clean up the resources after our test
     await pool.destroy()
   })
 
   it('Verify ROUND_ROBIN strategy can be run in a dynamic pool', async () => {
+    const workerChoiceStrategy = WorkerChoiceStrategies.ROUND_ROBIN
     const pool = new DynamicThreadPool(
       min,
       max,
       './tests/worker-files/thread/testWorker.js',
-      { workerChoiceStrategy: WorkerChoiceStrategies.ROUND_ROBIN }
+      { workerChoiceStrategy }
     )
     // TODO: Create a better test to cover `RoundRobinWorkerChoiceStrategy#choose`
     const promises = new Set()
@@ -272,46 +339,43 @@ describe('Selection strategies test suite', () => {
     for (const workerNode of pool.workerNodes) {
       expect(workerNode.usage).toStrictEqual({
         tasks: {
-          executed: maxMultiplier,
+          executed: expect.any(Number),
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
         runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
+      expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
+      expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
+        max * maxMultiplier
+      )
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        WorkerChoiceStrategies.ROUND_ROBIN
-      ).nextWorkerNodeId
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
     ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toBe(pool.workerNodes.length - 1)
     // We need to clean up the resources after our test
     await pool.destroy()
   })
@@ -351,14 +415,24 @@ describe('Selection strategies test suite', () => {
     )
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
-      ).nextWorkerNodeId
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBeDefined()
     pool.setWorkerChoiceStrategy(workerChoiceStrategy)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBe(0)
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -369,14 +443,24 @@ describe('Selection strategies test suite', () => {
     )
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
-      ).nextWorkerNodeId
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBeDefined()
     pool.setWorkerChoiceStrategy(workerChoiceStrategy)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBe(0)
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -390,7 +474,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -400,7 +485,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -482,34 +568,22 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
         runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
@@ -542,34 +616,22 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
         runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
@@ -589,7 +651,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -599,7 +662,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -681,42 +745,38 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: 0,
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
-        waitTime: {
-          aggregate: expect.any(Number),
-          average: 0,
-          median: 0,
+        }),
+        waitTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.waitTime.aggregate).toBeGreaterThanOrEqual(0)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.waitTime.aggregate == null) {
+        expect(workerNode.usage.waitTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.waitTime.aggregate).toBeGreaterThan(0)
+      }
     }
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -743,42 +803,38 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: 0,
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
-        waitTime: {
-          aggregate: expect.any(Number),
-          average: 0,
-          median: 0,
+        }),
+        waitTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.waitTime.aggregate).toBeGreaterThanOrEqual(0)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.waitTime.aggregate == null) {
+        expect(workerNode.usage.waitTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.waitTime.aggregate).toBeGreaterThan(0)
+      }
     }
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -792,7 +848,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -802,7 +859,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -884,42 +942,44 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
         runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
-        elu: {
-          idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
+        elu: expect.objectContaining({
+          idle: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          active: {
-            aggregate: expect.any(Number),
-            average: 0,
-            median: 0,
+          }),
+          active: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          utilization: expect.any(Number)
-        }
+          })
+        })
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      if (workerNode.usage.elu.active.aggregate == null) {
+        expect(workerNode.usage.elu.active.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.active.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.idle.aggregate == null) {
+        expect(workerNode.usage.elu.idle.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.idle.aggregate).toBeGreaterThanOrEqual(0)
+      }
+      if (workerNode.usage.elu.utilization == null) {
+        expect(workerNode.usage.elu.utilization).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
+        expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      }
     }
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -946,42 +1006,44 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
         runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
-        elu: {
-          idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
+        elu: expect.objectContaining({
+          idle: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          active: {
-            aggregate: expect.any(Number),
-            average: 0,
-            median: 0,
+          }),
+          active: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          utilization: expect.any(Number)
-        }
+          })
+        })
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      if (workerNode.usage.elu.active.aggregate == null) {
+        expect(workerNode.usage.elu.active.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.active.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.idle.aggregate == null) {
+        expect(workerNode.usage.elu.idle.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.idle.aggregate).toBeGreaterThanOrEqual(0)
+      }
+      if (workerNode.usage.elu.utilization == null) {
+        expect(workerNode.usage.elu.utilization).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
+        expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      }
     }
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -995,7 +1057,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -1005,7 +1068,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: false
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -1087,44 +1151,54 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: expect.any(Number),
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
-        elu: {
-          idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
+        elu: expect.objectContaining({
+          idle: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          active: {
-            aggregate: expect.any(Number),
-            average: expect.any(Number),
-            median: 0,
+          }),
+          active: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          utilization: expect.any(Number)
-        }
+          })
+        })
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.runTime.average).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.runTime.average == null) {
+        expect(workerNode.usage.runTime.average).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.average).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.active.aggregate == null) {
+        expect(workerNode.usage.elu.active.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.active.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.idle.aggregate == null) {
+        expect(workerNode.usage.elu.idle.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.idle.aggregate).toBeGreaterThanOrEqual(0)
+      }
+      if (workerNode.usage.elu.utilization == null) {
+        expect(workerNode.usage.elu.utilization).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
+        expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      }
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1156,44 +1230,54 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: expect.any(Number),
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
-        elu: {
-          idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
+        elu: expect.objectContaining({
+          idle: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          active: {
-            aggregate: expect.any(Number),
-            average: expect.any(Number),
-            median: 0,
+          }),
+          active: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          utilization: expect.any(Number)
-        }
+          })
+        })
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.runTime.average).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.runTime.average == null) {
+        expect(workerNode.usage.runTime.average).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.average).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.active.aggregate == null) {
+        expect(workerNode.usage.elu.active.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.active.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.idle.aggregate == null) {
+        expect(workerNode.usage.elu.idle.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.idle.aggregate).toBeGreaterThanOrEqual(0)
+      }
+      if (workerNode.usage.elu.utilization == null) {
+        expect(workerNode.usage.elu.utilization).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
+        expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      }
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1230,44 +1314,54 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: 0,
-          median: expect.any(Number),
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
-        elu: {
-          idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
+        elu: expect.objectContaining({
+          idle: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          active: {
-            aggregate: expect.any(Number),
-            average: expect.any(Number),
-            median: 0,
+          }),
+          active: expect.objectContaining({
             history: expect.any(CircularArray)
-          },
-          utilization: expect.any(Number)
-        }
+          })
+        })
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.runTime.median).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.runTime.median == null) {
+        expect(workerNode.usage.runTime.median).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.median).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.active.aggregate == null) {
+        expect(workerNode.usage.elu.active.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.active.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.elu.idle.aggregate == null) {
+        expect(workerNode.usage.elu.idle.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.idle.aggregate).toBeGreaterThanOrEqual(0)
+      }
+      if (workerNode.usage.elu.utilization == null) {
+        expect(workerNode.usage.elu.utilization).toBeUndefined()
+      } else {
+        expect(workerNode.usage.elu.utilization).toBeGreaterThanOrEqual(0)
+        expect(workerNode.usage.elu.utilization).toBeLessThanOrEqual(1)
+      }
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1305,12 +1399,12 @@ describe('Selection strategies test suite', () => {
     pool.setWorkerChoiceStrategy(workerChoiceStrategy)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).workersVirtualTaskEndTimestamp
     ).toBeInstanceOf(Array)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).workersVirtualTaskEndTimestamp.length
     ).toBe(0)
     await pool.destroy()
@@ -1340,12 +1434,12 @@ describe('Selection strategies test suite', () => {
     pool.setWorkerChoiceStrategy(workerChoiceStrategy)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).workersVirtualTaskEndTimestamp
     ).toBeInstanceOf(Array)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).workersVirtualTaskEndTimestamp.length
     ).toBe(0)
     // We need to clean up the resources after our test
@@ -1360,7 +1454,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: true
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -1370,7 +1465,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: true
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -1452,43 +1548,49 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: expect.any(Number),
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThanOrEqual(0)
-      expect(workerNode.usage.runTime.average).toBeGreaterThanOrEqual(0)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.runTime.average == null) {
+        expect(workerNode.usage.runTime.average).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.average).toBeGreaterThan(0)
+      }
     }
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
@@ -1524,43 +1626,49 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: expect.any(Number),
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
-      expect(workerNode.usage.runTime.average).toBeGreaterThan(0)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.runTime.average == null) {
+        expect(workerNode.usage.runTime.average).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.average).toBeGreaterThan(0)
+      }
     }
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
@@ -1601,43 +1709,49 @@ describe('Selection strategies test suite', () => {
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: expect.any(Number),
-          average: 0,
-          median: expect.any(Number),
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
       expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
       expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
         max * maxMultiplier
       )
-      expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
-      expect(workerNode.usage.runTime.median).toBeGreaterThan(0)
+      if (workerNode.usage.runTime.aggregate == null) {
+        expect(workerNode.usage.runTime.aggregate).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.aggregate).toBeGreaterThan(0)
+      }
+      if (workerNode.usage.runTime.median == null) {
+        expect(workerNode.usage.runTime.median).toBeUndefined()
+      } else {
+        expect(workerNode.usage.runTime.median).toBeGreaterThan(0)
+      }
     }
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
@@ -1661,7 +1775,12 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).nextWorkerNodeKey
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBeDefined()
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1677,7 +1796,12 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1686,7 +1810,7 @@ describe('Selection strategies test suite', () => {
     ).toBeGreaterThan(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).workerVirtualTaskRunTime
     ).toBe(0)
     await pool.destroy()
@@ -1698,7 +1822,12 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).nextWorkerNodeKey
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBeDefined()
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1714,7 +1843,12 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1723,7 +1857,7 @@ describe('Selection strategies test suite', () => {
     ).toBeGreaterThan(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).workerVirtualTaskRunTime
     ).toBe(0)
     // We need to clean up the resources after our test
@@ -1739,7 +1873,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: true
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     await pool.destroy()
     pool = new DynamicThreadPool(
@@ -1749,7 +1884,8 @@ describe('Selection strategies test suite', () => {
       { workerChoiceStrategy }
     )
     expect(pool.workerChoiceStrategyContext.getStrategyPolicy()).toStrictEqual({
-      useDynamicWorker: true
+      dynamicWorkerUsage: false,
+      dynamicWorkerReady: true
     })
     // We need to clean up the resources after our test
     await pool.destroy()
@@ -1767,8 +1903,8 @@ describe('Selection strategies test suite', () => {
       pool.workerChoiceStrategyContext.getTaskStatisticsRequirements()
     ).toStrictEqual({
       runTime: {
-        aggregate: false,
-        average: false,
+        aggregate: true,
+        average: true,
         median: false
       },
       waitTime: {
@@ -1793,8 +1929,8 @@ describe('Selection strategies test suite', () => {
       pool.workerChoiceStrategyContext.getTaskStatisticsRequirements()
     ).toStrictEqual({
       runTime: {
-        aggregate: false,
-        average: false,
+        aggregate: true,
+        average: true,
         median: false
       },
       waitTime: {
@@ -1831,40 +1967,32 @@ describe('Selection strategies test suite', () => {
     for (const workerNode of pool.workerNodes) {
       expect(workerNode.usage).toStrictEqual({
         tasks: {
-          executed: maxMultiplier,
+          executed: expect.any(Number),
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
+      expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
+      expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
+        max * maxMultiplier
+      )
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1879,8 +2007,18 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).workerNodeId
     ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toEqual(expect.any(Number))
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
@@ -1914,40 +2052,32 @@ describe('Selection strategies test suite', () => {
     for (const workerNode of pool.workerNodes) {
       expect(workerNode.usage).toStrictEqual({
         tasks: {
-          executed: maxMultiplier,
+          executed: expect.any(Number),
           executing: 0,
           queued: 0,
           maxQueued: 0,
+          stolen: 0,
           failed: 0
         },
-        runTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
+        runTime: expect.objectContaining({
           history: expect.any(CircularArray)
-        },
+        }),
         waitTime: {
-          aggregate: 0,
-          average: 0,
-          median: 0,
-          history: expect.any(CircularArray)
+          history: new CircularArray()
         },
         elu: {
           idle: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
+            history: new CircularArray()
           },
           active: {
-            aggregate: 0,
-            average: 0,
-            median: 0,
-            history: expect.any(CircularArray)
-          },
-          utilization: 0
+            history: new CircularArray()
+          }
         }
       })
+      expect(workerNode.usage.tasks.executed).toBeGreaterThanOrEqual(0)
+      expect(workerNode.usage.tasks.executed).toBeLessThanOrEqual(
+        max * maxMultiplier
+      )
     }
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -1962,8 +2092,18 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).workerNodeId
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
     ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
+    ).toEqual(expect.any(Number))
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
@@ -1992,7 +2132,17 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).workerNodeId
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBeDefined()
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -2007,13 +2157,23 @@ describe('Selection strategies test suite', () => {
     pool.setWorkerChoiceStrategy(workerChoiceStrategy)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).roundId
     ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).workerNodeId
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -2022,7 +2182,7 @@ describe('Selection strategies test suite', () => {
     ).toBeGreaterThan(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).roundWeights
     ).toStrictEqual([
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -2043,7 +2203,17 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).workerNodeId
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBeDefined()
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBeDefined()
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -2059,7 +2229,22 @@ describe('Selection strategies test suite', () => {
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
         pool.workerChoiceStrategyContext.workerChoiceStrategy
-      ).nextWorkerNodeId
+      ).roundId
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).workerNodeId
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).nextWorkerNodeKey
+    ).toBe(0)
+    expect(
+      pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
+      ).previousWorkerNodeKey
     ).toBe(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
@@ -2068,7 +2253,7 @@ describe('Selection strategies test suite', () => {
     ).toBeGreaterThan(0)
     expect(
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(
-        workerChoiceStrategy
+        pool.workerChoiceStrategyContext.workerChoiceStrategy
       ).roundWeights
     ).toStrictEqual([
       pool.workerChoiceStrategyContext.workerChoiceStrategies.get(