Why streams handle event logs in Redis - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an event to a Redis stream named 'mystream'.

Redis

XADD mystream * event [1]

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

Astart

Bstart_time

Cstart_event

Dstart_value

Attempts:

3 left

💡 Hint

Common Mistakes

Using a complex or incorrect event name.

Forgetting the asterisk (*) for automatic ID generation.

The command XADD mystream * event start adds an event named 'start' to the stream 'mystream'. The asterisk * lets Redis generate the event ID automatically.

2fill in blank

medium

Complete the code to read the latest event from the Redis stream 'mystream'.

Redis

XREVRANGE mystream + - COUNT [1]

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

A5

B10

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT 0 which returns no events.

Using a large COUNT when only one event is needed.

The command XREVRANGE mystream + - COUNT 1 reads the most recent event from the stream.

3fill in blank

hard

Fix the error in the command to read events from 'mystream' starting from ID '0-0'.

Redis

XRANGE mystream [1] +

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

A0

B0-0

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '0' instead of '0-0' as the start ID.

Using '-' or '*' which are not valid start IDs.

The command XRANGE mystream 0-0 + reads all events from the beginning of the stream.

4fill in blank

hard

Fill both blanks to create a consumer group named 'mygroup' for the stream 'mystream' starting from the beginning.

Redis

XGROUP CREATE mystream [1] [2]

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

Amygroup

B0

C0-0

D$

Attempts:

3 left

💡 Hint

Common Mistakes

Using '0' instead of '0-0' as the starting ID.

Using '$' which starts from the latest event.

The command XGROUP CREATE mystream mygroup 0-0 creates a consumer group named 'mygroup' starting from the first event in the stream.

5fill in blank

hard

Fill all three blanks to read new messages from 'mystream' for consumer 'consumer1' in group 'mygroup'.

Redis

XREADGROUP GROUP [1] [2] COUNT 1 STREAMS mystream [3]

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

Amygroup

Bconsumer1

C>

D0-0

Attempts:

3 left

💡 Hint

Common Mistakes

Using '0-0' instead of '>' which reads all messages from the start.

Mixing up group and consumer names.

The command XREADGROUP GROUP mygroup consumer1 COUNT 1 STREAMS mystream > reads new messages that have never been delivered to any consumer in the group.