Instances-rs

Disclaimer

This crate is being made for learning purposes. Any feedback is welcome.

Overview

instances-rs is a crate for making the application aware of how many of its instances its online.

Usage

To use instances-rs, add the following to your Cargo.toml: [NOT PUBLISHED YET]

[dependencies]
instances-rs = "0.1"

Then build the Instances object that will start updating the current instance info and fetching the other ones data. (See usability_test.rs for example)

use instances_rs::config::Builder;
use std::time::Duration;

fn main() {
    let instances_rs = Builder::default()
        .with_update_interval(Duration::from_secs(10))
        .with_backend(...) // One backend of your choose
        .with_info_extractor(...) // Some function that will extract the current instance data that you want to publish
        .build();

    // Optionally you can wait for
    instances_rs
        .wait_for_first_update(Duration::from_secs(10))
        .unwrap();

    // To get the info about the current instance
    instances_rs.get_instance_info();

    // To get the instance count
    instances_rs.instances_count();

    // List all active instances
    instances_rs.list_active_instances();
}

Data extractor

You can choose wherever data you like to publish with your instance data. The only restriction is that it must be Serializable and Deserializable.

Example:

    .with_info_extractor(|| env::consts::OS.to_string())

Backends

You can choose one of the available backends to store the instances' data or implement your own.

Right now there is no backend implemented, but I have plans to implement the following alternatives: MySQL, DynamoDB and Redis.

Leader strategy

You can classify your instances choosing one LeaderStrategy. By default LeaderStrategy::None is used.

Error strategy

You can choose one CommunicationErrorStrategy to handle error on updates.

• CommunicationErrorStrategy::Error will make the update return an Errto the daemon and all the instances' info will be unavailable.
• CommunicationErrorStrategy::UseLastInfo will emit a warning during the update and the outdated data will still be available.

License

This project is licensed under the MIT license.