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stefanwille / crystal-redis

Full featured Redis client for Crystal
MIT License
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Bug: Unusable in web context? #97

Closed gottlike closed 4 years ago

gottlike commented 4 years ago

I built a small web app that's supposed to go in production (first Crystal one, actually) and was stress-testing the backend with wrk.

That's when the backend was breaking down, throwing errors and hanging (but only for the routes where Redis is used). I noticed - among other things - that Redis commands were not in order anymore (e.g. a pipe command would have different responses from what was expected). So to me it looks like an issue regarding concurrency/timing.. maybe something like https://github.com/stefanwille/crystal-redis/issues/2, which @waj had fixed(?) quite a while ago.

Following I will paste code and instructions for reproduction:

shard.yml

removed

init_db.cr

removed

app.cr

removed

Then:

crystal run init_db.cr crystal run app.cr

wrk command for stress-testing: wrk -t2 -c20 -d5s http://localhost:1337/ (Maybe needs to be executed a few times, before hitting the issue)

After running wrk you will get timeouts and 500 responses when running simple curl http://localhost:1337/ commands.

This issue is framework independent - it occured with Raze as well as Kemal. Maybe of interest: I'm using (Ubuntu) Linux.

gottlike commented 4 years ago

I used Docker to run the following Redis instance:

docker run --rm -d -p 6379:6379/tcp redis:5.0.7-alpine3.11

gottlike commented 4 years ago

Okay, I just saw this: https://github.com/stefanwille/crystal-redis#connection-pooling

And after using Redis::PooledClient.new I can't reproduce the issue anymore :tada:

Maybe you would like to mention this in the readme as a requirement when using web frameworks :sweat_smile: