Crate thesis

Thesis provides the Experiment struct, which represents an experiment to run which compares the return values of multiple methods for accomplishing the same task.

Let’s imagine that we already have a function called load_data_from_db, which loads some data from a database. We want to refactor this to instead load the same data from redis. We write a new function called load_data_from_redis to accomplish the same task, but with redis instead of a DB. We want to use the redis version on only a very small percentage of traffic, say 0.5% of incoming requests, and we want to log it out if the redis data doesn’t match the DB data, treating the DB data as accurate and discarding the redis data if so. Here’s how we can use an Experiment to do this.

use thesis::{Experiment, rollout::Percent};

async fn load_data_from_db(id: i32) -> i32 { id }
async fn load_data_from_redis(id: i32) -> i32 { id }

let id = 4;
let result = Experiment::new("redis migration")
    .control(load_data_from_db(id))
    .experimental(load_data_from_redis(id))
    .rollout_strategy(Percent::new(0.5))
    .on_mismatch(|mismatch| {
        eprintln!(
            "DB & Redis data differ - db={}, redis={}",
            mismatch.control,
            mismatch.experimental,
        );

        // the `control` value here comes from the DB
        mismatch.control
    })
    .run()
    .await;

assert_eq!(result, 4);

Re-exports

pub use experiment::Experiment;

pub use rollout::RolloutDecision;

pub use rollout::RolloutStrategy;

pub use mismatch::MismatchHandler;

pub use mismatch::Mismatch;

Modules

experiment

mismatch

rollout