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Description

This error indicates that a background append-only file (AOF) rewrite process is already running. Redis only allows one AOF rewrite process to run at a time to prevent performance degradation.

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Error Message

ERR Background append only file rewriting already in progress

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Known Causes

3 known causes

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Concurrent BGREWRITE commands

Another `BGREWRITEAOF` command was issued while one was already in progress. Redis prevents overlapping rewrites.

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Scheduled BGREWRITE execution

Redis may automatically schedule an AOF rewrite based on configuration parameters. A manually triggered rewrite will fail if one is scheduled.

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Previous Rewrite Failure

A previous AOF rewrite might have failed and left a lock preventing new rewrites from starting.

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Solutions

3 solutions available

1. Wait for the Current AOF Rewrite to Complete easy

The error message explicitly states that a BGREWRITE is already in progress. The simplest solution is to wait for the current process to finish naturally. Redis will automatically start a new BGREWRITE when it's triggered again, provided no other rewrite is running.

1

Monitor Redis for the completion of the current BGREWRITE process. You can check the Redis log file for messages indicating the rewrite has started and finished.

2

Once the current BGREWRITE is complete, you can safely issue the BGREWRITE command again if needed. Check the Redis logs for confirmation that the previous rewrite has ended.

redis-cli BGREWRITEAOF

2. Check and Kill the Existing BGREWRITE Process (Advanced) advanced

If the BGREWRITE process seems stuck or is taking an excessively long time, you might consider forcefully terminating it. This should be done with extreme caution as it could lead to data inconsistencies if not managed properly. It's generally recommended to avoid this unless absolutely necessary and after understanding the risks.

1

Identify the Redis process ID (PID) on the server where Redis is running.

ps aux | grep redis-server

2

Within the output of the `ps aux | grep redis-server` command, look for a line that indicates a BGREWRITE is active. This might be visible in the command arguments or through Redis-specific monitoring tools if available.

3

If you are confident that the BGREWRITE process is indeed stuck and needs to be terminated, use the `kill` command with the appropriate signal. Sending `SIGTERM` first is a graceful way to attempt termination. If that doesn't work, `SIGKILL` can be used as a last resort.

kill <PID_of_redis_server>
# If SIGTERM doesn't work, use SIGKILL (use with caution):
kill -9 <PID_of_redis_server>

4

After killing the Redis process, restart Redis. Be aware that this will involve a full restart, and if AOF is enabled, Redis will likely need to rebuild the AOF file from the RDB snapshot or the remaining AOF entries upon startup, which might take time and could result in a temporary loss of data written during the last sync period.

3. Adjust BGREWRITE Triggers and Configuration medium

This error can occur if the conditions for automatic AOF rewrites are met too frequently, leading to overlapping processes. Reviewing and adjusting the `auto-aof-rewrite-percentage` and `auto-aof-rewrite-min-size` configuration parameters can help prevent this by making the triggers less sensitive.

1

Connect to your Redis instance using `redis-cli`.

redis-cli

2

View the current AOF rewrite trigger configuration.

CONFIG GET auto-aof-rewrite-percentage
CONFIG GET auto-aof-rewrite-min-size

3

If the current settings are too aggressive (e.g., a low percentage or small minimum size), consider increasing them. For example, to require a 100% increase in AOF size and a minimum size of 1GB:

CONFIG SET auto-aof-rewrite-percentage 100
CONFIG SET auto-aof-rewrite-min-size 1gb

4

To make these changes persistent across Redis restarts, you need to update your `redis.conf` file and reload the configuration or restart Redis.

vim /etc/redis/redis.conf
# Add or modify the following lines:
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 1gb

# Then reload or restart Redis:
redis-cli CONFIG REWRITE
# or restart the Redis service

Fix Redis BGREWRITE Error