Event replay in Microservices - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start event replay from a specific offset.

Microservices

eventStream.replayFrom([1])

Drag options to blanks, or click blank then click option'

Aoffset

BeventType

Ctimestamp

DeventId

Attempts:

3 left

💡 Hint

Common Mistakes

Using eventId instead of offset causes replay to start incorrectly.

Using timestamp may cause replay to miss events.

The replay starts from a specific offset in the event stream to ensure correct ordering.

2fill in blank

medium

Complete the code to store events for replay in a durable storage.

Microservices

eventStore.save([1])

Drag options to blanks, or click blank then click option'

AeventBatch

BeventHandler

CeventListener

DeventQueue

Attempts:

3 left

💡 Hint

Common Mistakes

Saving eventHandler instead of events causes no data to be stored.

Using eventQueue is for processing, not storage.

Events are saved in batches (eventBatch) to durable storage for replay.

3fill in blank

hard

Fix the error in the replay function to avoid duplicate event processing.

Microservices

if (lastProcessedEventId !== [1]) {
  processEvent(event)
}

Drag options to blanks, or click blank then click option'

Aevent.payload

Bevent.timestamp

Cevent.type

Devent.id

Attempts:

3 left

💡 Hint

Common Mistakes

Using event.timestamp causes duplicate events if timestamps are same.

Comparing event.type leads to skipping different events of same type.

Comparing with event.id ensures each event is processed once, avoiding duplicates.

4fill in blank

hard

Fill both blanks to filter and replay only specific event types.

Microservices

replayEvents.filter(event => event.[1] === [2])

Drag options to blanks, or click blank then click option'

Atype

B'UserCreated'

Cid

D'OrderPlaced'

Attempts:

3 left

💡 Hint

Common Mistakes

Filtering by 'id' instead of 'type' does not select event types.

Using wrong event type string filters no events.

Filtering by event.type equal to 'UserCreated' replays only those events.

5fill in blank

hard

Fill all three blanks to implement a replay with offset, batch size, and event handler.

Microservices

eventStream.replayFrom([1]).batch([2]).onEvent([3])

Drag options to blanks, or click blank then click option'

Aoffset

BbatchSize

ChandleEvent

DeventType

Attempts:

3 left

💡 Hint

Common Mistakes

Using eventType instead of batchSize causes errors in batch processing.

Omitting the event handler causes no events to be processed.

The replay starts from offset, processes events in batchSize chunks, and uses handleEvent to process each event.