BLPOP and BRPOP for blocking pop in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to pop the first element from the list 'tasks' using a blocking pop.

Redis

BLPOP tasks [1]

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

Atimeout

B1

C0

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-numeric string as timeout causes an error.

Using a positive number causes the command to timeout after that many seconds.

The BLPOP command requires a timeout value in seconds. Using 0 means it will block indefinitely until an element is available.

2fill in blank

medium

Complete the code to pop the last element from the list 'queue' with a 10-second timeout.

Redis

BRPOP queue [1]

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

A0

B5

Ctimeout

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 causes indefinite blocking, not a 10-second wait.

Using a string like 'timeout' causes an error.

The BRPOP command pops the last element and waits up to the specified timeout in seconds. Here, 10 means it waits 10 seconds before giving up.

3fill in blank

hard

Fix the error in the command to block pop from lists 'list1' and 'list2' with a 5-second timeout.

Redis

BLPOP [1] 5

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

Alist1 list2

Blist1,list2

Clist1;list2

Dlist1:list2

Attempts:

3 left

💡 Hint

Common Mistakes

Using commas or semicolons between keys causes syntax errors.

Using colons is invalid syntax.

The BLPOP command accepts multiple keys separated by spaces, not commas or other punctuation.

4fill in blank

hard

Fill both blanks to pop from 'mylist' with a 0-second timeout using BRPOP.

Redis

BRPOP [1] [2]

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

Amylist

B0

C5

Dtimeout

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-numeric timeout causes errors.

Using a positive timeout causes the command to stop waiting after that time.

The command BRPOP mylist 0 blocks indefinitely until an element is available in 'mylist'.

5fill in blank

hard

Fill all three blanks to pop from lists 'a', 'b' with a 3-second timeout using BLPOP.

Redis

BLPOP [1] [2] [3]

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

Aa

Bb

C3

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using commas between list names causes errors.

Using 0 as timeout blocks indefinitely, not 3 seconds.

The command BLPOP a b 3 blocks up to 3 seconds waiting for elements in lists 'a' or 'b'.