AOF (Append Only File) in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable AOF persistence in Redis configuration.

Redis

appendonly [1]

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

Ano

Byes

Cauto

Dmaybe

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no' disables AOF.

Using invalid values like 'auto' or 'maybe' causes errors.

Setting appendonly yes enables AOF persistence in Redis.

2fill in blank

medium

Complete the command to rewrite the AOF file manually.

Redis

redis-cli [1]

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

ABGREWRITEAOF

BBGSAVE

CSAVE

DFLUSHALL

Attempts:

3 left

💡 Hint

Common Mistakes

Using BGSAVE rewrites the RDB snapshot, not AOF.

SAVE blocks Redis and is not recommended for AOF rewriting.

The BGREWRITEAOF command triggers a background rewrite of the AOF file.

3fill in blank

hard

Fix the error in the AOF fsync policy setting.

Redis

appendfsync [1]

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

Aalways

Bsometimes

Ceverysec

Dnever

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sometimes' or 'never' which are invalid options.

Confusing 'always' with 'everysec' for performance.

The valid options for appendfsync are always, everysec, and no. everysec is the recommended setting for balancing performance and durability.

4fill in blank

hard

Fill both blanks to configure AOF rewrite thresholds.

Redis

auto-aof-rewrite-percentage [1]
auto-aof-rewrite-min-size [2]

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

A100

B64mb

C50

D128mb

Attempts:

3 left

💡 Hint

Common Mistakes

Setting percentage too high or too low.

Using invalid size units.

The default settings are auto-aof-rewrite-percentage 50 and auto-aof-rewrite-min-size 64mb to trigger AOF rewrite when the file grows 50% larger and is at least 64 MB.

5fill in blank

hard

Fill all three blanks to configure AOF persistence with safe fsync and rewrite settings.

Redis

appendonly [1]
appendfsync [2]
auto-aof-rewrite-percentage [3]

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

Ayes

Beverysec

C100

Dno

Attempts:

3 left

💡 Hint

Common Mistakes

Disabling AOF by setting appendonly to no.

Using unsafe fsync settings.

Setting rewrite percentage too low.

This configuration enables AOF persistence, sets fsync to every second for safety and performance, and triggers rewrite when AOF grows 100% larger.

Practice

1.

What is the main purpose of Redis AOF (Append Only File)?

easy

A. To save every write operation for data recovery

B. To compress data for faster network transfer

C. To create backups only once a day

D. To store data in a binary format

Solution

1. Step 1: Understand AOF functionality

   AOF logs every write command to a file to ensure data can be recovered after a crash.

2. Step 2: Compare options with AOF purpose

   Only To save every write operation for data recovery correctly describes saving every write operation for recovery.

3. Final Answer:

   To save every write operation for data recovery -> Option A

4. Quick Check:

   AOF saves writes = B [OK]

Hint: AOF logs all writes to recover data after crashes [OK]

Common Mistakes:

• Thinking AOF compresses data
• Confusing AOF with snapshot backups
• Believing AOF stores data in binary

2.

Which of the following is the correct Redis configuration directive to enable AOF persistence?

?

easy

A. enable_aof on

B. appendonly yes

C. persistence append

D. aof_enable true

Solution

1. Step 1: Recall Redis config syntax for AOF

   The correct directive to enable AOF is appendonly yes.

2. Step 2: Check other options for correctness

   Options A, B, and C are not valid Redis config directives.

3. Final Answer:

   appendonly yes -> Option B

4. Quick Check:

   Enable AOF with appendonly yes [OK]

Hint: Remember: 'appendonly yes' enables AOF in redis.conf [OK]

Common Mistakes:

• Using incorrect directive names
• Confusing AOF with RDB snapshot settings
• Using boolean words like true/on instead of yes

3.

Given the Redis AOF configuration appendfsync everysec, what is the expected behavior?

medium

A. Redis writes AOF data to disk every second

B. Redis never writes AOF data to disk

C. Redis writes every command to disk immediately

D. Redis writes AOF data only on shutdown

Solution

1. Step 1: Understand appendfsync everysec meaning

   This setting tells Redis to sync AOF data to disk once every second.

2. Step 2: Compare with other options

   Redis writes every command to disk immediately means immediate write (appendfsync always), B and D are incorrect behaviors.

3. Final Answer:

   Redis writes AOF data to disk every second -> Option A

4. Quick Check:

   everysec means sync once per second [OK]

Hint: everysec means disk sync once per second, not instantly [OK]

Common Mistakes:

• Confusing everysec with always
• Thinking it never writes to disk
• Assuming writes happen only on shutdown

4.

Identify the error in this Redis AOF configuration snippet:

appendonly yes
appendfsync everyminute

medium

A. appendonly should be no

B. appendfsync must be set to 'never'

C. appendfsync value 'everyminute' is invalid

D. No error, configuration is valid

Solution

1. Step 1: Check valid appendfsync values

   Valid values are 'always', 'everysec', or 'no'. 'everyminute' is not valid.

2. Step 2: Verify appendonly setting

   appendonly yes is correct to enable AOF.

3. Final Answer:

   appendfsync value 'everyminute' is invalid -> Option C

4. Quick Check:

   appendfsync accepts only always, everysec, or no [OK]

Hint: appendfsync only accepts always, everysec, or no [OK]

Common Mistakes:

• Assuming 'everyminute' is valid
• Thinking appendonly yes is wrong
• Believing appendfsync must be 'never'

5.

You want to ensure Redis AOF persistence is safe but also fast. Which configuration balances durability and performance best?

appendonly yes
appendfsync everysec

hard

A. appendonly no and appendfsync no

B. appendonly no and appendfsync always

C. appendonly yes and appendfsync no

D. appendonly yes and appendfsync everysec

Solution

1. Step 1: Understand durability vs performance

   appendonly yes enables AOF persistence; appendfsync everysec syncs data every second, balancing safety and speed.

2. Step 2: Evaluate other options

   Options B and D disable AOF, losing durability; appendonly yes and appendfsync no disables syncing, risking data loss.

3. Final Answer:

   appendonly yes and appendfsync everysec -> Option D

4. Quick Check:

   Enable AOF with everysec sync for balance [OK]

Hint: Use appendonly yes with everysec for good speed and safety [OK]

Common Mistakes:

• Disabling AOF for speed
• Using appendfsync no risking data loss
• Choosing appendfsync always causing slow writes