Subscription util tests (#1295)

* consecutive list tests

* flesh out subscription util tests

---------

Co-authored-by: Devin Ivy <[email protected]>

packages/bsky/tests/subscription/util.test.ts

@@ -0,0 +1,185 @@
+import { wait } from '@atproto/common'
+import {
+  ConsecutiveList,
+  LatestQueue,
+  PartitionedQueue,
+} from '../../src/subscription/util'
+import { randomStr } from '../../../crypto/src'
+
+describe('subscription utils', () => {
+  describe('ConsecutiveList', () => {
+    it('tracks consecutive complete items.', () => {
+      const consecutive = new ConsecutiveList<number>()
+      // add items
+      const item1 = consecutive.push(1)
+      const item2 = consecutive.push(2)
+      const item3 = consecutive.push(3)
+      expect(item1.isComplete).toEqual(false)
+      expect(item2.isComplete).toEqual(false)
+      expect(item3.isComplete).toEqual(false)
+      // complete items out of order
+      expect(consecutive.list.length).toBe(3)
+      expect(item2.complete()).toEqual([])
+      expect(item2.isComplete).toEqual(true)
+      expect(consecutive.list.length).toBe(3)
+      expect(item1.complete()).toEqual([1, 2])
+      expect(item1.isComplete).toEqual(true)
+      expect(consecutive.list.length).toBe(1)
+      expect(item3.complete()).toEqual([3])
+      expect(consecutive.list.length).toBe(0)
+      expect(item3.isComplete).toEqual(true)
+    })
+  })
+
+  describe('LatestQueue', () => {
+    it('only performs most recently queued item.', async () => {
+      const latest = new LatestQueue()
+      const complete: number[] = []
+      latest.add(async () => {
+        await wait(1)
+        complete.push(1)
+      })
+      latest.add(async () => {
+        await wait(1)
+        complete.push(2)
+      })
+      latest.add(async () => {
+        await wait(1)
+        complete.push(3)
+      })
+      latest.add(async () => {
+        await wait(1)
+        complete.push(4)
+      })
+      await latest.queue.onIdle()
+      expect(complete).toEqual([1, 4]) // skip 2, 3
+      latest.add(async () => {
+        await wait(1)
+        complete.push(5)
+      })
+      latest.add(async () => {
+        await wait(1)
+        complete.push(6)
+      })
+      await latest.queue.onIdle()
+      expect(complete).toEqual([1, 4, 5, 6])
+    })
+
+    it('stops processing queued messages on destroy.', async () => {
+      const latest = new LatestQueue()
+      const complete: number[] = []
+      latest.add(async () => {
+        await wait(1)
+        complete.push(1)
+      })
+      latest.add(async () => {
+        await wait(1)
+        complete.push(2)
+      })
+      const destroyed = latest.destroy()
+      latest.add(async () => {
+        await wait(1)
+        complete.push(3)
+      })
+      await destroyed
+      expect(complete).toEqual([1]) // 2 was cleared, 3 was after destroy
+      // show that waiting on destroyed above was already enough to reflect all complete items
+      await latest.queue.onIdle()
+      expect(complete).toEqual([1])
+    })
+  })
+
+  describe('PartitionedQueue', () => {
+    it('performs work in parallel across partitions, serial within a partition.', async () => {
+      const partitioned = new PartitionedQueue({ concurrency: Infinity })
+      const complete: number[] = []
+      // partition 1 items start slow but get faster: slow should still complete first.
+      partitioned.add('1', async () => {
+        await wait(10)
+        complete.push(11)
+      })
+      partitioned.add('1', async () => {
+        await wait(5)
+        complete.push(12)
+      })
+      partitioned.add('1', async () => {
+        await wait(1)
+        complete.push(13)
+      })
+      expect(partitioned.partitions.size).toEqual(1)
+      // partition 2 items complete quickly except the last, which is slowest of all events.
+      partitioned.add('2', async () => {
+        await wait(1)
+        complete.push(21)
+      })
+      partitioned.add('2', async () => {
+        await wait(1)
+        complete.push(22)
+      })
+      partitioned.add('2', async () => {
+        await wait(1)
+        complete.push(23)
+      })
+      partitioned.add('2', async () => {
+        await wait(15)
+        complete.push(24)
+      })
+      expect(partitioned.partitions.size).toEqual(2)
+      await partitioned.main.onIdle()
+      expect(complete).toEqual([21, 22, 23, 11, 12, 13, 24])
+      expect(partitioned.partitions.size).toEqual(0)
+    })
+
+    it('limits overall concurrency.', async () => {
+      const partitioned = new PartitionedQueue({ concurrency: 1 })
+      const complete: number[] = []
+      // if concurrency were not constrained, partition 1 would complete all items
+      // before any items from partition 2. since it is constrained, the work is complete in the order added.
+      partitioned.add('1', async () => {
+        await wait(1)
+        complete.push(11)
+      })
+      partitioned.add('2', async () => {
+        await wait(10)
+        complete.push(21)
+      })
+      partitioned.add('1', async () => {
+        await wait(1)
+        complete.push(12)
+      })
+      partitioned.add('2', async () => {
+        await wait(10)
+        complete.push(22)
+      })
+      // only partition 1 exists so far due to the concurrency
+      expect(partitioned.partitions.size).toEqual(1)
+      await partitioned.main.onIdle()
+      expect(complete).toEqual([11, 21, 12, 22])
+      expect(partitioned.partitions.size).toEqual(0)
+    })
+
+    it('settles with many items.', async () => {
+      const partitioned = new PartitionedQueue({ concurrency: 100 })
+      const complete: { partition: string; id: number }[] = []
+      const partitions = new Set<string>()
+      for (let i = 0; i < 500; ++i) {
+        const partition = randomStr(1, 'base16').slice(0, 1)
+        partitions.add(partition)
+        partitioned.add(partition, async () => {
+          await wait((i % 2) * 2)
+          complete.push({ partition, id: i })
+        })
+      }
+      expect(partitioned.partitions.size).toEqual(partitions.size)
+      await partitioned.main.onIdle()
+      expect(complete.length).toEqual(500)
+      for (const partition of partitions) {
+        const ids = complete
+          .filter((item) => item.partition === partition)
+          .map((item) => item.id)
+        expect(ids).toEqual([...ids].sort((a, b) => a - b))
+      }
+      expect(partitioned.partitions.size).toEqual(0)
+    })
+  })
+})