What is redis used for?

[marcelmindemann]

Hello,

the official docker-compose file sets up a redis container next to searxng:
https://github.com/searxng/searxng-docker/blob/master/docker-compose.yaml#L21

I've been trying to understand why exactly. The README does not say anything about why redis is needed.
The only two pages in the documentation I can find are:
https://docs.searxng.org/admin/architecture.html
and
https://docs.searxng.org/admin/engines/settings.html#redis
which say absoutely nothing about why redis is needed and what gets saved.
Out of curiosity, I disabled my redis container and started searxng. No problem, the containers comes up and seems functional. The redis is also empty after running searxng for some time as proven by redis-cli --scan.

Can I simply ignore redis, then? What are the implications?

[dalf]

Currently, SearXNG uses redis for two things:

• the limiter plugin: useful if you have a public instance, it blocks too many requests from the same IP and block obvious bots.
• the embedded checker, which checks if each of engine is working in your instance.

If you don't use these two features, you can disable the redis container.
In future, redis is going to store more things.

[Bag72]

I don't fully understand docker but I had an issue with Redis but SearXNG still worked. I fixed it and I looked at the docker-compose file given in 'Any working compose file #124' which is the compose file I was given originally. I don't see anywhere in there that points SearXNG to Redis and if you remove redis from the docker-compose it still works. Is it using Redis in the docker-compose file? If I connect to the contained and use redis-cli and type info it doesn't seem to change when I do any queries via SearXNG. Other times I've seen redis in a shared contained there has been a Redis_URL environment variable. How does this work without one?

[unixfox]

Redis is mainly being used for the anti bot built in SearXNG.

Apart from that, it is used in some engines like DDG for storing temporary data.

SearXNG works without redis because it's not mandatory yet, if searxng does not detect redis then it will try to do it without redis. But it's possible that it's in the future we are going to make redis mandatory. Obviously we will tell it to everyone before doing that.

[return42]

an additional note: without Redis, the defense against bots is inefficient .. if you have a public instance that is listed at searx.space, for example .. which anyone can access, then you should run the instance with Redis (and with bot-detection, aka limiter activated).

[Bag72]

Thank you for the replies. I'll leave it in then as I do have a public instance although not registered at searx.space. I'll turn on the bot-detection in the settings file as well. Just to be safe.

Is there a way I can test that it is linked to Redis and working correctly?

[return42]

utils/searxng.sh instance check

[Bag72]

Thank you.