Migrating from Redis 7.4+ to Valkey

There are many blog posts about your migration options from Redis to Valkey but if you’re wanting to do an in place swap, one thing that has come up is that Redis 7.4’s RDB format isn’t compatible with Redis so if you’ve upgraded Redis to 7.4, this complicates things a bit. I found myself in this exact situation which is described in this GitHub issue because I have been using the redis:7-alpine Docker image and auto-updating it when new versions are available. As user bigb4ng points out, there is a cli based tool, rdb-cli which can read data from a dump file and output it to a Valkey server to achieve your data migration. While not quite the swap that you might have been hoping for, it’s a nice workaround.

So why a blog post? Well, I found that the instructions for compiling rdb-cli were fine but details about the expected build environment weren’t great. If you know me, I am 100% going to build a Docker image to do just that which helped me figure out that Ubuntu 22.04 worked well for the use case after having issues on Debian Bookworm and Ubuntu 24.04. You can check out the GitHub repo (mbentley/docker-rdb-cli) where I have some basic instructions and a Dockerfile if you wish to build the image, otherwise it’s already available on Docker Hub.

Let’s do a quick walkthrough of what migration looks like using some basic Redis and Valkey containers to give you an idea of the process. We will create a Redis container, create some example data, ensure it is saved to disk, start up a Valkey container, migrate the data using rdb-cli to the valkey container, and then verify that the data was migrated.

Create a Redis container:

Note: Here, we are just using a Docker named volume redis-data for temporary data use. Adapt this method to your use case when performing your actual migration.
```
docker run -d \
  --name redis \
  -v redis-data:/data \
  redis:7-alpine
```
Write a few key/value pairs to have some data for validation:
```
docker exec -it redis redis-cli SET foo bar
docker exec -it redis redis-cli SET baz qux
```
Each command will output OK if successful.

Make sure to force Redis to save the data to the dump file:

# check when the last save was
$ docker exec -it redis redis-cli LASTSAVE
(integer) 1729871115

# initiate a non-blocking save
$ docker exec -it redis redis-cli BGSAVE
Background saving started

# check when the last save was to verify it had completed
$ docker exec -it redis redis-cli LASTSAVE
(integer) 1729871385

Stop the redis docker container:
```
docker stop -t 30 redis
```

Start a Valkey docker container:

docker run -d \
  --name valkey \
  -v valkey-data:/data \
  valkey/valkey:8-alpine

Verify that there is no data in our Valkey container’s database:
```
docker exec -it valkey valkey-cli KEYS '*'
```
This should return (empty array).

Using the persistent data volume from the redis container, run the rdb-cli command:

Note: we are re-using the container network from the valkey container so that it’s available as localhost; this simplifies our experiment.

docker run -it --rm \
  --network=container:valkey \
  -v redis-data:/data \
  -w /data \
  mbentley/rdb-cli \
    rdb-cli /data/dump.rdb -l /dev/stdout redis -h 127.0.0.1 -p 6379

This will output something similar to this, indicating that it can parse the RDB file:

INFO  : RDBX_createReaderFile: Initialized with file /data/dump.rdb
INFO  : Finalizing parser configuration
INFO  : Number sets of handlers registered at level RAW/STRUCT/DATA: 1/0/1
INFO  : Start processing RDB source
INFO  : The parsed RDB file version is: 12
WARN  : Target Redis version is not configured! Set it to Redis version: 7.4
INFO  : rdbversion=12
INFO  : Parser done

Verify that the data has been transferred to our Valkey container’s database:
```
docker exec -it valkey valkey-cli KEYS '*'
```
You should see a response of the two keys that should have been migrated from redis:
```
1) "foo"
2) "baz"
```
Now that you’re done, you can cleanup from our test migration.

Remove the containers:
```
docker rm -f redis valkey
```
Remove the volumes:
```
docker volume rm redis-data valkey-data
```
Remove the images:
```
docker rmi redis:7-alpine valkey/valkey:8-alpine
```

You might want to perform some more detailed testing but for my use, this method has worked for me to migrate a number of Redis instances.