feat(spans): parameterize redis spans

[DominikB2014]

Work towards #cach

First pass to parameterize redis spans, there is still a lot of other commands to consider, and improvements to be made, but if we merge this we can audit the cardinality and real data.

Also in a future PR we will have to tag the scrubbed keys as well.

[jjbayer]

Because correctly parsing string literals is hard, I have a suggestion for simplification: What if we always only parametrize the first key, and make everything else "*"? With something like

let scrubbed_args = if let Some((first, rest)) = args.split_once(" ") {
    if first.starts_with('"') || first.starts_with('\'') { // It's a string literal
        "*".to_owned()
    } else {
        let mut result = parameterize_redis_key(first);
        result.push_str(" ");
        result.push_str(rest);
    }
}

you would not need split_string_with_quotes at all.

[DominikB2014]

I get the intention, but i'm hesitant in only parameterizing the first key. The plan is to show metrics for each key namespace, in the scenario where you often perform a command that touches many keys, the metrics would be incorrect.

I am open to trying this out first, as its much simpler and we can audit to see what the data really looks like!

[phacops]

I'm with @jjbayer on this.

You should also not really distinguish between the single and multi argument commands. I'd parse the command then replace everything with a * and then we can re-evaluate and specialize based on commands perhaps.

Redis has a somewhat easy protocol to understand. If we need to extract more from this, we can look at the definitions of each command and parse it properly. I wouldn't be surprised if there weren't a library doing that already in Rust.

[DominikB2014]

For v0 we are really looking to get some level of key grouping here, so ideally we don't replace everything except the command with a *. I'm okay to just try @jjbayer suggestion and only parametrize the first key.

[phacops]

There are a lot more commands than this in Redis. We should try to parse them in a more generic fashion.

[phacops]

I'm with @jjbayer on this.

You should also not really distinguish between the single and multi argument commands. I'd parse the command then replace everything with a * and then we can re-evaluate and specialize based on commands perhaps.

Redis has a somewhat easy protocol to understand. If we need to extract more from this, we can look at the definitions of each command and parse it properly. I wouldn't be surprised if there weren't a library doing that already in Rust.

[jjbayer]

@DominikB2014 is this PR still relevant? Or can we close it?

[DominikB2014]

@DominikB2014 is this PR still relevant? Or can we close it?

@jjbayer not needed, I'll close it!