Redis renderer

[kaihendry]

I'm curious if anyone has written a Redis renderer, since I have configuration not unlike https://docs.konghq.com/hub/kong-inc/rate-limiting/configuration/ and currently Redis keys are maintained manually by operations and can cause operational issues.

[HT154]

This is an interesting problem space! Pkl can only produce textual output, but there are a couple it may be able to help:

• Shell command generation - a simple technique here might be to have Pkl produce a shell script that runs redis-cli commands. A custom renderer of this kind is easy to build in-language. You would run it like pkl eval <module> | bash.
• Language binding library - using the Java/Kotlin library, pkl-swift, or pkl-go write a program where the Pkl module is evaluated into types in the target language. The program would use this result and a Redis client library to write the values.

[kaihendry]

Do you have an example of how to produce said shell script please?

[HT154]

Sure, it's fairly straightforward. Using your pkl-redis repo as the basis:

module Control

hidden baseCommand: String = "redis-cli" // could be "docker exec redis redis-cli"
hidden dbNum: UInt = 0

rl: Controller;
cb: Controller;

class Controller {
  toggle: Running = "OFF";
}

typealias Running = "ON"|"OFF"|"SHADOW"

/// Flatten an object structure down to "key:path"="value" pairs
function walkKV(val: Map|Mapping|Dynamic|Typed): Mapping<String, Any> = new {
  for (k, v in val.toMap()) {
    when (v is Map|Mapping|Dynamic|Typed) {
      for (k2, v2 in walkKV(v)) {
        ["\(k):\(k2)"] = v2
      }
    } else {
      // not clear how List|Listing should be handled here, pretend they don't exist
      [k] = v
    }
  }
}

output {
  text = new Listing {
    "#!/bin/bash"
    for (k, v in walkKV(module)) {
      "\(baseCommand) -n \(dbNum) SET \(k) '\(v)'"
    }
  }.join("\n")
}

Then to run it

pkl eval config.pkl | bash

[kaihendry]

Did I get the idea of the "Language binding library" over at https://github.com/kaihendry/pkl-redis ?

[HT154]

In general, yeah! My original thought was to directly use go-redis or similar for tighter integration instead of printing out the shell commands to run.