AP-5046 outbox-core package for transactional outbox pattern

packages/outbox-core/README.md

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+# outbox-core
+
+Main package that contains the core functionality of the Outbox pattern to provide "at least once" delivery semantics for messages.
+
+## Installation
+
+```bash
+npm i -S @message-queue-toolkit/outbox-core
+```
+
+## Usage
+
+To process outbox entries and emit them to the message queue, you need to create an instance of the `OutboxPeriodicJob` class:
+
+```typescript
+import { OutboxPeriodicJob } from '@message-queue-toolkit/outbox-core';
+
+const job = new OutboxPeriodicJob(
+    //Implementation of OutboxStorage interface, TODO: Point to other packages in message-queue-toolkit
+    outboxStorage, 
+    //Default available accumulator for gathering outbox entries as the process job is progressing.
+    new InMemoryOutboxAccumulator(),
+    //DomainEventEmitter, it will be used to publish events, see @message-queue-toolkit/core
+    eventEmitter,
+    //See PeriodicJobDependencies from @lokalise/background-jobs-common
+    dependencies,
+    //Retry count, how many times outbox entries should be retried to be processed
+    3,
+    //emitBatchSize - how many outbox entries should be emitted at once
+    10,
+    //internalInMs - how often the job should be executed, e.g. below it runs every 1sec
+    1000
+)
+```
+
+Job will take care of processing outbox entries emitted by:
+```typescript
+import {
+  type CommonEventDefinition,
+  enrichMessageSchemaWithBase,
+} from '@message-queue-toolkit/schemas'
+
+const MyEvents = {
+  created: {
+    ...enrichMessageSchemaWithBase(
+      'entity.created',
+      z.object({
+        message: z.string(),
+      }),
+    ),
+  },
+} as const satisfies Record<string, CommonEventDefinition>
+
+type MySupportedEvents = (typeof TestEvents)[keyof typeof TestEvents][]
+
+const emitter = new OutboxEventEmitter<MySupportedEvents>(
+    //Same instance of outbox storage that is used by OutboxPeriodicJob
+    outboxStorage
+)
+
+//It pushes the entry to the storage, later will be picked up by the OutboxPeriodicJob
+await emitter.emit(/* args */)
+```

packages/outbox-core/index.ts

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+export * from './lib/outbox'
+export * from './lib/objects'
+export * from './lib/accumulators'
+export * from './lib/storage'

packages/outbox-core/lib/accumulators.ts

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+import type { CommonEventDefinition } from '@message-queue-toolkit/schemas'
+import type { OutboxEntry } from './objects.ts'
+
+/**
+ * Accumulator is responsible for storing outbox entries in two cases:
+ * - successfully dispatched event
+ * - failed events
+ *
+ * Thanks to this, we can use aggregated result and persist in the storage in batches.
+ */
+export interface OutboxAccumulator<SupportedEvents extends CommonEventDefinition[]> {
+  /**
+   * Accumulates successfully dispatched event.
+   * @param outboxEntry
+   */
+  add(outboxEntry: OutboxEntry<SupportedEvents[number]>): Promise<void>
+
+  /**
+   * Accumulates failed event.
+   * @param outboxEntry
+   */
+  addFailure(outboxEntry: OutboxEntry<SupportedEvents[number]>): Promise<void>
+
+  /**
+   * Returns all entries that should be persisted as successful ones.
+   */
+  getEntries(): Promise<OutboxEntry<SupportedEvents[number]>[]>
+
+  /**
+   * Returns all entries that should be persisted as failed ones. Such entries will be retried + their retryCount will be incremented.
+   */
+  getFailedEntries(): Promise<OutboxEntry<SupportedEvents[number]>[]>
+
+  /**
+   * After running clear(), no entries should be returned by getEntries() and getFailedEntries().
+   *
+   * clear() is always called after flush() in OutboxStorage.
+   */
+  clear(): Promise<void>
+}
+
+export class InMemoryOutboxAccumulator<SupportedEvents extends CommonEventDefinition[]>
+  implements OutboxAccumulator<SupportedEvents>
+{
+  private entries: OutboxEntry<SupportedEvents[number]>[] = []
+  private failedEntries: OutboxEntry<SupportedEvents[number]>[] = []
+
+  public add(outboxEntry: OutboxEntry<SupportedEvents[number]>) {
+    this.entries.push(outboxEntry)
+
+    return Promise.resolve()
+  }
+
+  public addFailure(outboxEntry: OutboxEntry<SupportedEvents[number]>) {
+    this.failedEntries.push(outboxEntry)
+
+    return Promise.resolve()
+  }
+
+  getEntries(): Promise<OutboxEntry<SupportedEvents[number]>[]> {
+    return Promise.resolve(this.entries)
+  }
+
+  getFailedEntries(): Promise<OutboxEntry<SupportedEvents[number]>[]> {
+    return Promise.resolve(this.failedEntries)
+  }
+
+  public clear(): Promise<void> {
+    this.entries = []
+    this.failedEntries = []
+    return Promise.resolve()
+  }
+}

packages/outbox-core/lib/objects.ts

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+import type {
+  CommonEventDefinition,
+  CommonEventDefinitionPublisherSchemaType,
+  ConsumerMessageMetadataType,
+} from '@message-queue-toolkit/schemas'
+
+/**
+ * Status of the outbox entry.
+ * - CREATED - entry was created and is waiting to be processed to publish actual event
+ * - ACKED - entry was picked up by outbox job and is being processed
+ * - SUCCESS - entry was successfully processed, event was published
+ * - FAILED - entry processing failed, it will be retried
+ */
+export type OutboxEntryStatus = 'CREATED' | 'ACKED' | 'SUCCESS' | 'FAILED'
+
+export type OutboxEntry<SupportedEvent extends CommonEventDefinition> = {
+  id: string
+  event: SupportedEvent
+  data: Omit<CommonEventDefinitionPublisherSchemaType<SupportedEvent>, 'type'>
+  precedingMessageMetadata?: Partial<ConsumerMessageMetadataType>
+  status: OutboxEntryStatus
+  created: Date
+  updated?: Date
+  retryCount: number
+}

packages/outbox-core/lib/outbox.ts

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+import type { PeriodicJobDependencies } from '@lokalise/background-jobs-common'
+import { AbstractPeriodicJob, type JobExecutionContext } from '@lokalise/background-jobs-common'
+import type {
+  CommonEventDefinition,
+  CommonEventDefinitionPublisherSchemaType,
+  ConsumerMessageMetadataType,
+  DomainEventEmitter,
+} from '@message-queue-toolkit/core'
+import { PromisePool } from '@supercharge/promise-pool'
+import { uuidv7 } from 'uuidv7'
+import type { OutboxAccumulator } from './accumulators'
+import type { OutboxEntry } from './objects'
+import type { OutboxStorage } from './storage'
+
+export type OutboxDependencies<SupportedEvents extends CommonEventDefinition[]> = {
+  outboxStorage: OutboxStorage<SupportedEvents>
+  outboxAccumulator: OutboxAccumulator<SupportedEvents>
+  eventEmitter: DomainEventEmitter<SupportedEvents>
+}
+
+export type OutboxProcessorConfiguration = {
+  maxRetryCount: number
+  emitBatchSize: number
+}
+
+export type OutboxConfiguration = {
+  jobIntervalInMs: number
+} & OutboxProcessorConfiguration
+
+/**
+ * Main logic for handling outbox entries.
+ *
+ * If entry is rejected, it is NOT going to be handled during the same execution. Next execution will pick it up.
+ */
+export class OutboxProcessor<SupportedEvents extends CommonEventDefinition[]> {
+  constructor(
+    private readonly outboxDependencies: OutboxDependencies<SupportedEvents>,
+    private readonly outboxProcessorConfiguration: OutboxProcessorConfiguration,
+  ) {}
+
+  public async processOutboxEntries(context: JobExecutionContext) {
+    const { outboxStorage, eventEmitter, outboxAccumulator } = this.outboxDependencies
+
+    const entries = await outboxStorage.getEntries(this.outboxProcessorConfiguration.maxRetryCount)
+
+    const filteredEntries =
+      entries.length === 0 ? entries : await this.getFilteredEntries(entries, outboxAccumulator)
+
+    await PromisePool.for(filteredEntries)
+      .withConcurrency(this.outboxProcessorConfiguration.emitBatchSize)
+      .process(async (entry) => {
+        try {
+          await eventEmitter.emit(entry.event, entry.data, entry.precedingMessageMetadata)
+          await outboxAccumulator.add(entry)
+        } catch (e) {
+          context.logger.error({ error: e }, 'Failed to process outbox entry.')
+
+          await outboxAccumulator.addFailure(entry)
+        }
+      })
+
+    await outboxStorage.flush(outboxAccumulator)
+    await outboxAccumulator.clear()
+  }
+
+  private async getFilteredEntries(
+    entries: OutboxEntry<SupportedEvents[number]>[],
+    outboxAccumulator: OutboxAccumulator<SupportedEvents>,
+  ) {
+    const currentEntriesInAccumulator = new Set(
+      (await outboxAccumulator.getEntries()).map((entry) => entry.id),
+    )
+    return entries.filter((entry) => !currentEntriesInAccumulator.has(entry.id))
+  }
+}
+
+/**
+ * Periodic job that processes outbox entries every "intervalInMs". If processing takes longer than defined interval, another subsequent job WILL NOT be started.
+ *
+ * When event is published, and then entry is accumulated into SUCCESS group. If processing fails, entry is accumulated as FAILED and will be retried.
+ *
+ * Max retry count is defined by the user.
+ */
+/* c8 ignore start */
+export class OutboxPeriodicJob<
+  SupportedEvents extends CommonEventDefinition[],
+> extends AbstractPeriodicJob {
+  private readonly outboxProcessor: OutboxProcessor<SupportedEvents>
+
+  constructor(
+    outboxDependencies: OutboxDependencies<SupportedEvents>,
+    outboxConfiguration: OutboxConfiguration,
+    dependencies: PeriodicJobDependencies,
+  ) {
+    super(
+      {
+        jobId: 'OutboxJob',
+        schedule: {
+          intervalInMs: outboxConfiguration.jobIntervalInMs,
+        },
+        singleConsumerMode: {
+          enabled: true,
+        },
+      },
+      {
+        redis: dependencies.redis,
+        logger: dependencies.logger,
+        transactionObservabilityManager: dependencies.transactionObservabilityManager,
+        errorReporter: dependencies.errorReporter,
+        scheduler: dependencies.scheduler,
+      },
+    )
+
+    this.outboxProcessor = new OutboxProcessor<SupportedEvents>(
+      outboxDependencies,
+      outboxConfiguration,
+    )
+  }
+
+  protected async processInternal(context: JobExecutionContext): Promise<void> {
+    await this.outboxProcessor.processOutboxEntries(context)
+  }
+}
+/* c8 ignore stop */
+
+export class OutboxEventEmitter<SupportedEvents extends CommonEventDefinition[]> {
+  constructor(private storage: OutboxStorage<SupportedEvents>) {}
+
+  /**
+   * Persists outbox entry in persistence layer, later it will be picked up by outbox job.
+   * @param supportedEvent
+   * @param data
+   * @param precedingMessageMetadata
+   */
+  public async emit<SupportedEvent extends SupportedEvents[number]>(
+    supportedEvent: SupportedEvent,
+    data: Omit<CommonEventDefinitionPublisherSchemaType<SupportedEvent>, 'type'>,
+    precedingMessageMetadata?: Partial<ConsumerMessageMetadataType>,
+  ) {
+    await this.storage.createEntry({
+      id: uuidv7(),
+      event: supportedEvent,
+      data,
+      precedingMessageMetadata,
+      status: 'CREATED',
+      created: new Date(),
+      retryCount: 0,
+    })
+  }
+}

packages/outbox-core/lib/storage.ts

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+import type { CommonEventDefinition } from '@message-queue-toolkit/schemas'
+import type { OutboxAccumulator } from './accumulators'
+import type { OutboxEntry } from './objects'
+
+/**
+ * Takes care of persisting and retrieving outbox entries.
+ *
+ * Implementation is required:
+ * - in order to fulfill at least once delivery guarantee, persisting entries should be performed inside isolated transaction
+ * - to return entries in the order they were created (UUID7 is used to create entries in OutboxEventEmitter)
+ * - returned entries should not include the ones with 'SUCCESS' status
+ */
+export interface OutboxStorage<SupportedEvents extends CommonEventDefinition[]> {
+  createEntry(
+    outboxEntry: OutboxEntry<SupportedEvents[number]>,
+  ): Promise<OutboxEntry<SupportedEvents[number]>>
+
+  /**
+   * Responsible for taking all entries from the accumulator and persisting them in the storage.
+   *
+   * - Items that are in OutboxAccumulator::getEntries MUST be changed to SUCCESS status and `updatedAt` field needs to be set.
+   * - Items that are in OutboxAccumulator::getFailedEntries MUST be changed to FAILED status, `updatedAt` field needs to be set and retryCount needs to be incremented.
+   */
+  flush(outboxAccumulator: OutboxAccumulator<SupportedEvents>): Promise<void>
+
+  /**
+   * Returns entries in the order they were created. It doesn't return entries with 'SUCCESS' status. It doesn't return entries that have been retried more than maxRetryCount times.
+   *
+   * For example if entry retryCount is 1 and maxRetryCount is 1, entry MUST be returned. If it fails again then retry count is 2, in that case entry MUST NOT be returned.
+   */
+  getEntries(maxRetryCount: number): Promise<OutboxEntry<SupportedEvents[number]>[]>
+}