Rust SDK - Installation

The Rust SDK is published to crates.io as westyx-nexus. There is no custom registry - cargo resolves the crate directly from crates.io.

Install

cargo add westyx-nexus
cargo add tokio --features rt-multi-thread,macros

Or add it manually:

[dependencies]
westyx-nexus = "0.14.0-beta.2"
tokio = { version = "1", features = ["rt-multi-thread", "macros"] }

Then import it:

use westyx_nexus::{NexusClient, NexusConfig, NexusError};

Features

Feature	Default	What it adds
`blocking`	off	`westyx_nexus::blocking::NexusClient` - the same surface synchronously, for applications with no async runtime
`aws-iam`	off	The `aws_iam` WIF provider (AWS IAM Caller Identity) for non-EKS AWS compute; pulls in the official AWS credential and SigV4 crates

westyx-nexus = { version = "0.14.0-beta.2", features = ["blocking"] }
westyx-nexus = { version = "0.14.0-beta.2", features = ["aws-iam"] }

A default build carries neither, so it pulls no AWS dependency and creates no runtime of its own.

Requirements

Rust 1.88 or newer. The floor is measured against the crate’s real dependency set and the language features it uses, and a CI job builds and tests with exactly that toolchain on every pipeline.
Network access to crates.io (or a mirror) at build time, and to <your-slug>.api.westyx.dev at runtime.

With aws-iam enabled, the AWS crates resolve against the same floor. The SDK repository sets resolver.incompatible-rust-versions = "fallback"; add the same option to your .cargo/config.toml if you enable that feature while pinning an older toolchain, so the newest AWS releases - which require a far newer compiler - are not selected for you.

TLS

TLS is rustls, reqwest 0.13’s default backend, so the SDK has no OpenSSL system dependency and certificate verification uses the platform trust store.

Dependencies

The SDK brings in a focused set:

Crate	Version	Purpose
`reqwest`	`0.13`	Async HTTP client, rustls TLS
`tokio`	`1.x`	Timers, tasks and async locks
`tracing`	`0.1`	Structured spans and events
`serde` + `serde_json`	`1.x`	JSON serialisation and the `Value` type
`thiserror`	`2.x`	Derive macro for `NexusError`
`percent-encoding`	`2.x`	URL encoding for secret key segments
`url`	`2.x`	Endpoint parsing and validation
`tempfile`	`3.x`	The private, mode-`0700` directory for materialised file-type secrets

With aws-iam: aws-config, aws-credential-types, aws-sigv4, aws-smithy-runtime-api.

Async and blocking

The client is async. In an axum or actix handler, clone it and use it directly:

let client = client.clone();
tokio::spawn(async move {
    let value = client.get_config("some.key"); // synchronous cache read
    let _ = value;
});

Cache reads (get_config, get_flag, get_secret, …) are synchronous because they read in-memory state; they never block on the network, so no spawn_blocking wrapper is needed - if you have one from v0.10.x, remove it. Without a runtime of your own, enable the blocking feature:

use westyx_nexus::{blocking::NexusClient, NexusConfig};

let client = NexusClient::create(NexusConfig {
    api_key: std::env::var("NEXUS_API_KEY")?,
    endpoint: std::env::var("NEXUS_ENDPOINT")?,
    ..Default::default()
})?;
let secret = client.get_secret("stripe.key")?;

The blocking client owns a small runtime on its own threads, so its calls also work from inside someone else’s runtime.

OpenFeature provider

westyx-nexus-openfeature = "0.14.0-beta.2"
open-feature = "0.3"

See OpenFeature.

Verifying installation

cargo tree -p westyx-nexus

Verifying connectivity

curl -s \
  -H "X-Nexus-API-Key: wxs_..." \
  https://your-slug.api.westyx.dev/v1/sync

A valid response returns a JSON snapshot with your configs, secrets and flags. An HTTP 401 means the key is wrong; HTTP 404 means the slug is wrong. To watch the live SSE stream:

curl -N \
  -H "X-Nexus-API-Key: wxs_..." \
  -H "Accept: text/event-stream" \
  https://your-slug.api.westyx.dev/v1/stream

You should see event:resync arrive within a second, then a : ping keepalive every 30 seconds. Press Ctrl+C to stop.

Troubleshooting

The crate name is westyx-nexus (hyphens); the Rust import uses underscores: use westyx_nexus::.... This is standard Cargo behaviour.

error[E0432]: unresolved import - ensure the dependency is in Cargo.toml and run cargo build at least once.
could not find 'westyx-nexus' in the registry - check network access to crates.io, or run cargo update.
package requires rustc 1.88 - upgrade your toolchain: rustup update stable.
`create` is not async, or missing .await - v0.11 made the client async; see Async migration.

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

Rust SDK - Installation

Install

Features

Requirements

TLS

Dependencies

Async and blocking

OpenFeature provider

Verifying installation

Verifying connectivity

Troubleshooting

​Install

​Features

​Requirements

​TLS

​Dependencies

​Async and blocking

​OpenFeature provider

​Verifying installation

​Verifying connectivity

​Troubleshooting

Install

Features

Requirements

TLS

Dependencies

Async and blocking

OpenFeature provider

Verifying installation

Verifying connectivity

Troubleshooting