diff --git a/Cargo.lock b/Cargo.lock index 76f2dfa4..58117b75 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -4561,9 +4561,9 @@ dependencies = [ "async-nats", "axum", "futures-util", - "reqwest 0.13.1", "serde", "serde_json", + "swarm-queue-client", "tokio", "tracing", "tracing-subscriber", @@ -4591,6 +4591,19 @@ dependencies = [ "tracing-subscriber", ] +[[package]] +name = "swarm-queue-client" +version = "0.1.0" +dependencies = [ + "async-nats", + "reqwest 0.13.1", + "serde", + "serde_json", + "thiserror 2.0.18", + "tokio", + "tracing", +] + [[package]] name = "swarmctl" version = "0.1.0" diff --git a/Cargo.toml b/Cargo.toml index 5b85aa74..2f0ff283 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -23,6 +23,7 @@ members = [ "hivectl", "swarm-controller", "swarm-nats-auth", + "swarm-queue-client", "swarmctl", ] @@ -84,6 +85,7 @@ hive-host-sock = { path = "hive-host-sock" } hive-priv-sock = { path = "hive-priv-sock" } hive-sock-client = { path = "hive-sock-client" } hive-types = { path = "hive-types" } +swarm-queue-client = { path = "swarm-queue-client" } thiserror = "2" tower-http = { version = "0.7", features = ["fs"] } uuid = { version = "1", features = ["v4"] } diff --git a/swarm-controller/Cargo.toml b/swarm-controller/Cargo.toml index 507858d3..c5012025 100644 --- a/swarm-controller/Cargo.toml +++ b/swarm-controller/Cargo.toml @@ -18,9 +18,13 @@ anyhow.workspace = true async-nats = { workspace = true, features = ["kv"] } axum.workspace = true futures-util.workspace = true -reqwest.workspace = true serde.workspace = true serde_json.workspace = true +# The queue connect (token mint + auth callback + reconnect) is shared with +# every other participant - a hive publishing its own status runs the same +# code with a different client id. Two copies of credential handling is one +# token-refresh fix that has to be found twice. +swarm-queue-client.workspace = true tokio.workspace = true tracing.workspace = true tracing-subscriber.workspace = true diff --git a/swarm-controller/src/main.rs b/swarm-controller/src/main.rs index dd42e1f7..3c9e675e 100644 --- a/swarm-controller/src/main.rs +++ b/swarm-controller/src/main.rs @@ -31,7 +31,6 @@ use serde::{Deserialize, Serialize}; use utoipa::{OpenApi, ToSchema}; use utoipa_axum::{router::OpenApiRouter, routes}; -mod queue; mod status; /// Where the daemon binds, overridable via `SWARM_CONTROLLER_SOCKET`. @@ -298,12 +297,12 @@ async fn main() -> Result<()> { // a half-set environment — `QueueConfig::from_env` refuses that, because // silently behaving like an unconfigured host is how every hive ends up // reading `never_reported` with nothing to point at. - let status = match queue::QueueConfig::from_env()? { + let status = match swarm_queue_client::QueueConfig::from_env("SWARM_CONTROLLER")? { None => { tracing::info!("no swarm queue configured; status aggregation is off"); None } - Some(cfg) => match queue::connect(cfg).await { + Some(cfg) => match swarm_queue_client::connect(cfg).await { Ok(client) => { // NOT "connected": `retry_on_initial_connect` returns a client // before any connection has been established, so claiming a @@ -319,7 +318,13 @@ async fn main() -> Result<()> { ))) } Err(e) => { - tracing::warn!(error = format!("{e:#}"), "swarm queue unreachable"); + // `chain`, not `{:#}`: this is the queue client's own + // error type, and thiserror's Display ignores the + // alternate flag — the source would be dropped silently. + tracing::warn!( + error = swarm_queue_client::chain(&e), + "swarm queue unreachable" + ); None } }, diff --git a/swarm-controller/src/queue.rs b/swarm-controller/src/queue.rs deleted file mode 100644 index 6291f43d..00000000 --- a/swarm-controller/src/queue.rs +++ /dev/null @@ -1,206 +0,0 @@ -//! The controller's client end of the swarm message queue. -//! -//! The queue admits every non-responder client through `auth_callout`: a -//! client presents a token at CONNECT, the callout responder introspects it -//! against authelia and mints a user JWT if it is good. So the controller is -//! an ordinary client and needs an identity of its own — it is not a hive, and -//! the per-hive clients issued from the roster are not its to use. -//! -//! Two things about that shape drive everything here: -//! -//! - **A token expires.** Authelia issues `client_credentials` access tokens -//! with `expires_in: 3599`. Authentication happens at CONNECT, so a -//! long-lived connection is fine — but a *reconnect* an hour later needs a -//! token that was minted an hour later. -//! - **`async-nats` re-runs an auth callback per connection attempt** (it is -//! handed that attempt's nonce). So the refresh belongs in the callback and -//! not in a timer: there is no window in which the client holds a token it -//! minted for a previous connection. -//! -//! The alternative — mint once, pass a static `auth_token`, own the reconnect -//! loop — fails in the way this subsystem exists to prevent: the controller -//! keeps serving, its status data quietly stops updating, and nothing says so -//! until someone reads a dashboard. - -use std::path::PathBuf; - -use anyhow::{Context, Result, bail}; - -/// Only the one field this needs; authelia returns several. -#[derive(serde::Deserialize)] -struct TokenResponse { - access_token: String, -} - -/// Where the controller finds the queue and what it authenticates with. -/// -/// Every field comes from an environment variable the NixOS module sets, the -/// same way `load_hives` takes the roster — a config change is a redeploy, and -/// this process reads no file it was not pointed at. -#[derive(Debug, Clone)] -pub struct QueueConfig { - /// `nats://host:port` for the swarm queue. - pub url: String, - /// Authelia's token endpoint, e.g. `https://auth./api/oidc/token`. - pub token_endpoint: String, - /// The controller's own `OAuth2` client id. - pub client_id: String, - /// File holding the client secret's PLAINTEXT. - /// - /// A path and not a value: the secret is minted on the authelia host and - /// read here, and putting it in the environment would publish it to - /// anything that can read `/proc//environ`. - pub client_secret_file: PathBuf, -} - -impl QueueConfig { - /// Read the config from the environment, or `None` when the queue was not - /// wired up for this deployment. - /// - /// `None` rather than an error on purpose: the controller serves its HTTP - /// surface on hosts where the queue is not enabled, and refusing to start - /// there would trade a missing feature for a dead daemon. What must NOT - /// happen is a *half* configuration silently behaving like an absent one — - /// hence the explicit partial check below. - pub fn from_env() -> Result> { - let url = std::env::var("SWARM_CONTROLLER_NATS_URL").ok(); - let token_endpoint = std::env::var("SWARM_CONTROLLER_OIDC_TOKEN_ENDPOINT").ok(); - let client_id = std::env::var("SWARM_CONTROLLER_OIDC_CLIENT_ID").ok(); - let secret = std::env::var("SWARM_CONTROLLER_OIDC_CLIENT_SECRET_FILE").ok(); - - match (url, token_endpoint, client_id, secret) { - (None, None, None, None) => Ok(None), - (Some(url), Some(token_endpoint), Some(client_id), Some(secret)) => Ok(Some(Self { - url, - token_endpoint, - client_id, - client_secret_file: PathBuf::from(secret), - })), - // A partially-set environment is a deployment bug, and the failure - // it would otherwise produce is the expensive kind: the controller - // comes up "fine", never connects, and every hive reads as having - // never reported. Naming the missing variables costs one line. - _ => bail!( - "swarm queue is half-configured: SWARM_CONTROLLER_NATS_URL, \ - _OIDC_TOKEN_ENDPOINT, _OIDC_CLIENT_ID and \ - _OIDC_CLIENT_SECRET_FILE must be set together or not at all" - ), - } - } -} - -/// Mint a fresh access token for the controller's own client. -/// -/// `client_credentials`, because there is no user here: the controller -/// authenticates as itself. Authelia refuses the `openid` scope for this grant -/// (a machine client receives an access token and never an id-token), so no -/// scope is requested. -async fn mint_token(http: &reqwest::Client, cfg: &QueueConfig) -> Result { - // Read per call rather than caching: the file is small, and a cached - // secret would survive a rotation that the operator believes took effect. - let secret = tokio::fs::read_to_string(&cfg.client_secret_file) - .await - .with_context(|| { - format!( - "reading the queue client secret from {}", - cfg.client_secret_file.display() - ) - })?; - - let response = http - .post(&cfg.token_endpoint) - .form(&[ - ("grant_type", "client_credentials"), - ("client_id", cfg.client_id.as_str()), - ("client_secret", secret.trim()), - ]) - .send() - .await - .context("requesting an access token from authelia")?; - - // The body carries authelia's own error description, and it is far more - // useful than the status alone: a wrong grant says `unauthorized_client`, - // a wrong secret says `invalid_client`, and those point at different - // config. - let status = response.status(); - let body = response.text().await.unwrap_or_default(); - if !status.is_success() { - bail!("authelia refused the controller's token request ({status}): {body}"); - } - - let parsed: TokenResponse = - serde_json::from_str(&body).context("parsing authelia's token response")?; - Ok(parsed.access_token) -} - -/// Connect to the swarm queue, minting a token for each connection attempt. -pub async fn connect(cfg: QueueConfig) -> Result { - // A timeout, because this client runs INSIDE the auth callback: a token - // endpoint that accepts the connection and then never answers would hang - // the callback, and with it the connection attempt that invoked it, with - // no retry and nothing in the log to say why. Failing fast lets - // `async-nats` do what it already does well — back off and try again. - // 10s is generous for a form POST to a local IdP. - let http = reqwest::Client::builder() - .timeout(std::time::Duration::from_secs(10)) - .build() - .context("building the token-endpoint HTTP client")?; - let url = cfg.url.clone(); - - let client = async_nats::ConnectOptions::with_auth_callback(move |_nonce| { - let http = http.clone(); - let cfg = cfg.clone(); - async move { - let token = mint_token(&http, &cfg) - .await - // The callback's error type carries a string, so the context - // chain would be lost; flatten it rather than dropping it. - .map_err(|e| async_nats::AuthError::new(format!("{e:#}")))?; - let mut auth = async_nats::Auth::new(); - auth.token = Some(token); - Ok(auth) - } - }) - // The controller and the queue are separate units on (possibly) - // separate hosts, and nothing orders them. Without this, a queue that - // comes up one second later leaves the controller permanently - // queue-less until someone restarts it — a boot-order race that - // presents as "status has been unavailable since Tuesday". - // - // It also composes with the callback above rather than fighting it: - // each background attempt is a connection attempt, so each one mints - // its own token instead of retrying a stale one. - .retry_on_initial_connect() - .connect(&url) - .await - .with_context(|| format!("connecting to the swarm queue at {url}"))?; - - Ok(client) -} - -#[cfg(test)] -mod tests { - use super::*; - - /// The all-unset case is the common one — most hosts do not run the queue. - #[test] - fn an_absent_environment_is_not_an_error() { - // Guard: this test would pass vacuously inside a configured - // environment, so it asserts the variables really are unset first. - for k in [ - "SWARM_CONTROLLER_NATS_URL", - "SWARM_CONTROLLER_OIDC_TOKEN_ENDPOINT", - "SWARM_CONTROLLER_OIDC_CLIENT_ID", - "SWARM_CONTROLLER_OIDC_CLIENT_SECRET_FILE", - ] { - if std::env::var(k).is_ok() { - return; - } - } - assert!( - QueueConfig::from_env() - .expect("absent is not an error") - .is_none() - ); - } -} diff --git a/swarm-queue-client/Cargo.toml b/swarm-queue-client/Cargo.toml new file mode 100644 index 00000000..32a2d0e5 --- /dev/null +++ b/swarm-queue-client/Cargo.toml @@ -0,0 +1,23 @@ +[package] +name = "swarm-queue-client" +version.workspace = true +readme = "README.md" +edition.workspace = true + +[dependencies] +# No `kv`/`jetstream` feature here on purpose: this crate's job ends at a +# connected client. What a consumer does with it - KV for the controller and +# the hive, plain messaging for anything later - is the consumer's business, +# and its Cargo.toml is where that requirement should be visible. +async-nats.workspace = true +reqwest.workspace = true +serde.workspace = true +serde_json.workspace = true +# A library, so its errors are a matchable enum rather than an opaque +# `anyhow::Error`. The binaries that consume this keep anyhow; `?` converts. +thiserror.workspace = true +tokio.workspace = true +tracing.workspace = true + +[lints] +workspace = true diff --git a/swarm-queue-client/README.md b/swarm-queue-client/README.md new file mode 100644 index 00000000..79230794 --- /dev/null +++ b/swarm-queue-client/README.md @@ -0,0 +1,55 @@ +# swarm-queue-client + +Connecting to the swarm message queue as an authenticated client. Shared by +every process that participates: the swarm controller reads hive status out of +the queue, a hive publishes its own status into it. + +## Why a crate and not a module per binary + +The *connect* is identical for every participant — mint an authelia token, +present it at CONNECT for the `auth_callout` responder to introspect, let +`async-nats` re-run the callback on each connection attempt. Only the **use** +differs. + +Two copies of that would be two copies of credential handling, and a +token-refresh fix would have to be found twice. The same reasoning already put +`hive-sock-client` in its own crate rather than in each daemon that speaks to a +unix socket. + +## The two properties that constrain the code + +**A token expires.** Authelia issues `client_credentials` access tokens with +`expires_in: 3599`. Authentication happens at CONNECT, so a long-lived +connection is fine — but a *reconnect* an hour later needs a token minted an +hour later. + +**The refresh therefore lives in the auth callback, not in a timer.** +`async-nats` invokes it per connection attempt, so there is no window in which +the client holds a token it minted for a previous connection. The alternative — +mint once, own the reconnect loop — fails in the way this subsystem exists to +prevent: the process keeps serving while its data quietly stops moving, and +nothing says so until someone reads a dashboard. + +## Configuration + +`QueueConfig::from_env(prefix)` reads `_NATS_URL`, +`_OIDC_TOKEN_ENDPOINT`, `_OIDC_CLIENT_ID` and +`_OIDC_CLIENT_SECRET_FILE`. + +The prefix is a parameter because the variables belong to the consuming unit — +a NixOS module sets them alongside its other options. What is shared is the +rule, not the spelling: **all four together or none at all.** A half-set +environment is a hard error, because the failure it would otherwise produce is +the expensive kind — the process comes up "fine", never connects, and the data +it was supposed to move silently stops. + +The client secret is a **path, not a value**: putting it in the environment +would publish it to anything that can read `/proc//environ`. It is read +per token request rather than cached, so a rotation the operator believes took +effect actually did. + +## What this crate does not do + +It ends at a connected client. No `jetstream`/`kv` feature is enabled here — +what a consumer does with the connection is its own business, and its +`Cargo.toml` is where that requirement should be visible. diff --git a/swarm-queue-client/src/lib.rs b/swarm-queue-client/src/lib.rs new file mode 100644 index 00000000..94a4af0d --- /dev/null +++ b/swarm-queue-client/src/lib.rs @@ -0,0 +1,316 @@ +//! Connecting to the swarm message queue as an authenticated client. +//! +//! Shared by every process that needs the queue — the swarm controller reads +//! hive status out of it, a hive publishes its own status into it — because +//! the *connect* is identical for all of them and only the use differs. +//! Duplicating it per binary would put credential handling in two places, and +//! a token-refresh fix would then have to be found twice. +//! +//! The queue admits every non-responder client through `auth_callout`: a +//! client presents a token at CONNECT, the callout responder introspects it +//! against authelia and mints a user JWT if it is good. So each participant is +//! an ordinary client that needs an identity of its own — the controller is +//! not a hive, and the per-hive clients issued from the roster are not its to +//! use. +//! +//! Two things about that shape drive everything here: +//! +//! - **A token expires.** Authelia issues `client_credentials` access tokens +//! with `expires_in: 3599`. Authentication happens at CONNECT, so a +//! long-lived connection is fine — but a *reconnect* an hour later needs a +//! token that was minted an hour later. +//! - **`async-nats` re-runs an auth callback per connection attempt** (it is +//! handed that attempt's nonce). So the refresh belongs in the callback and +//! not in a timer: there is no window in which the client holds a token it +//! minted for a previous connection. +//! +//! The alternative — mint once, pass a static `auth_token`, own the reconnect +//! loop — fails in the way this subsystem exists to prevent: the controller +//! keeps serving, its status data quietly stops updating, and nothing says so +//! until someone reads a dashboard. + +use std::path::PathBuf; + +/// Everything that can go wrong reaching the swarm queue. +/// +/// `thiserror` and not `anyhow` because this is a library: a caller gets a +/// type it can match on, and the binaries that consume it keep using +/// `anyhow` — `?` converts for free, so nothing downstream is more verbose +/// for it. The same split `hive-claude` uses. +/// +/// The variants are the failures an operator acts on differently: a +/// half-configured environment is a deployment bug, a refused token is an +/// identity-provider config problem, an unreachable queue is a network +/// one. Collapsing them into one string would make that distinction a +/// matter of reading prose. +#[derive(Debug, thiserror::Error)] +pub enum Error { + #[error( + "swarm queue is half-configured: {prefix}_NATS_URL, \ + {prefix}_OIDC_TOKEN_ENDPOINT, {prefix}_OIDC_CLIENT_ID and \ + {prefix}_OIDC_CLIENT_SECRET_FILE must be set together or not at all" + )] + PartialConfig { prefix: String }, + + #[error("reading the queue client secret from {path}")] + ClientSecret { + path: String, + #[source] + source: std::io::Error, + }, + + #[error("building the token-endpoint HTTP client")] + HttpClient(#[source] reqwest::Error), + + #[error("requesting an access token from authelia")] + TokenRequest(#[source] reqwest::Error), + + /// The body carries authelia's own `error_description`, and it is far + /// more useful than the status alone: a wrong grant says + /// `unauthorized_client`, a wrong secret says `invalid_client`, and + /// those point at different config. + #[error("authelia refused the token request ({status}): {body}")] + TokenRefused { + status: reqwest::StatusCode, + body: String, + }, + + #[error("parsing authelia's token response")] + TokenResponse(#[source] serde_json::Error), + + #[error("connecting to the swarm queue at {url}")] + Connect { + url: String, + #[source] + source: async_nats::ConnectError, + }, +} + +/// Render an error and its source chain on one line. +/// +/// **Use this instead of `{:#}` anywhere an [`Error`] is rendered without +/// first being `?`-converted into an `anyhow::Error`.** `anyhow`'s +/// `Display` special-cases `f.alternate()` to walk the source chain; +/// `thiserror`'s derive does not, so `{e:#}` and `{e}` render +/// identically for this type. A call site that formatted an +/// `anyhow::Error` with `{:#}` and now holds an [`Error`] therefore keeps +/// compiling, keeps looking right, and silently drops the cause — which +/// is the half that says *why*, and is exactly what a one-shot boot +/// warning with no retry needs most. +/// +/// Public for that reason: the fix cannot live only inside this crate's +/// own auth callback while the callers it was written for reach for +/// `{:#}` and get nothing. +pub fn chain(error: &dyn std::error::Error) -> String { + let mut rendered = error.to_string(); + let mut source = error.source(); + while let Some(cause) = source { + rendered.push_str(": "); + rendered.push_str(&cause.to_string()); + source = cause.source(); + } + rendered +} + +/// Only the one field this needs; authelia returns several. +#[derive(serde::Deserialize)] +struct TokenResponse { + access_token: String, +} + +/// Where the controller finds the queue and what it authenticates with. +/// +/// Every field comes from an environment variable the NixOS module sets, the +/// same way `load_hives` takes the roster — a config change is a redeploy, and +/// this process reads no file it was not pointed at. +#[derive(Debug, Clone)] +pub struct QueueConfig { + /// `nats://host:port` for the swarm queue. + pub url: String, + /// Authelia's token endpoint, e.g. `https://auth./api/oidc/token`. + pub token_endpoint: String, + /// The controller's own `OAuth2` client id. + pub client_id: String, + /// File holding the client secret's PLAINTEXT. + /// + /// A path and not a value: the secret is minted on the authelia host and + /// read here, and putting it in the environment would publish it to + /// anything that can read `/proc//environ`. + pub client_secret_file: PathBuf, +} + +impl QueueConfig { + /// Read the config from `_NATS_URL`, `_OIDC_TOKEN_ENDPOINT`, + /// `_OIDC_CLIENT_ID` and `_OIDC_CLIENT_SECRET_FILE`, or + /// `None` when the queue was not wired up for this deployment. + /// + /// The prefix is a parameter rather than a constant because the variables + /// belong to the *consuming unit* — a NixOS module sets them alongside its + /// other options, and two daemons sharing one name would be a worse + /// coupling than passing four characters. What is shared is the RULE + /// below, not the spelling. + /// + /// `None` rather than an error on purpose: a daemon serves its other + /// surfaces on hosts where the queue is not enabled, and refusing to start + /// there would trade a missing feature for a dead process. What must NOT + /// happen is a *half* configuration silently behaving like an absent one — + /// hence the explicit partial check below. + pub fn from_env(prefix: &str) -> Result, Error> { + let url = std::env::var(format!("{prefix}_NATS_URL")).ok(); + let token_endpoint = std::env::var(format!("{prefix}_OIDC_TOKEN_ENDPOINT")).ok(); + let client_id = std::env::var(format!("{prefix}_OIDC_CLIENT_ID")).ok(); + let secret = std::env::var(format!("{prefix}_OIDC_CLIENT_SECRET_FILE")).ok(); + + match (url, token_endpoint, client_id, secret) { + (None, None, None, None) => Ok(None), + (Some(url), Some(token_endpoint), Some(client_id), Some(secret)) => Ok(Some(Self { + url, + token_endpoint, + client_id, + client_secret_file: PathBuf::from(secret), + })), + // A partially-set environment is a deployment bug, and the failure + // it would otherwise produce is the expensive kind: the process + // comes up "fine", never connects, and the data it was supposed to + // move silently stops moving. Naming the variables costs one line. + _ => Err(Error::PartialConfig { + prefix: prefix.to_owned(), + }), + } + } +} + +/// Mint a fresh access token for the controller's own client. +/// +/// `client_credentials`, because there is no user here: the controller +/// authenticates as itself. Authelia refuses the `openid` scope for this grant +/// (a machine client receives an access token and never an id-token), so no +/// scope is requested. +async fn mint_token(http: &reqwest::Client, cfg: &QueueConfig) -> Result { + // Read per call rather than caching: the file is small, and a cached + // secret would survive a rotation that the operator believes took effect. + let secret = tokio::fs::read_to_string(&cfg.client_secret_file) + .await + .map_err(|source| Error::ClientSecret { + path: cfg.client_secret_file.display().to_string(), + source, + })?; + + let response = http + .post(&cfg.token_endpoint) + .form(&[ + ("grant_type", "client_credentials"), + ("client_id", cfg.client_id.as_str()), + ("client_secret", secret.trim()), + ]) + .send() + .await + .map_err(Error::TokenRequest)?; + + // Why the body and not just the status: see `Error::TokenRefused`. + let status = response.status(); + let body = response.text().await.unwrap_or_default(); + if !status.is_success() { + return Err(Error::TokenRefused { status, body }); + } + + let parsed: TokenResponse = serde_json::from_str(&body).map_err(Error::TokenResponse)?; + Ok(parsed.access_token) +} + +/// Connect to the swarm queue, minting a token for each connection attempt. +pub async fn connect(cfg: QueueConfig) -> Result { + // A timeout, because this client runs INSIDE the auth callback: a token + // endpoint that accepts the connection and then never answers would hang + // the callback, and with it the connection attempt that invoked it, with + // no retry and nothing in the log to say why. Failing fast lets + // `async-nats` do what it already does well — back off and try again. + // 10s is generous for a form POST to a local IdP. + let http = reqwest::Client::builder() + .timeout(std::time::Duration::from_secs(10)) + .build() + .map_err(Error::HttpClient)?; + let url = cfg.url.clone(); + + let client = async_nats::ConnectOptions::with_auth_callback(move |_nonce| { + let http = http.clone(); + let cfg = cfg.clone(); + async move { + let token = mint_token(&http, &cfg) + .await + // The callback's error type carries a string, so the source + // chain would be lost; flatten it rather than dropping it. + .map_err(|e| async_nats::AuthError::new(chain(&e)))?; + let mut auth = async_nats::Auth::new(); + auth.token = Some(token); + Ok(auth) + } + }) + // The controller and the queue are separate units on (possibly) + // separate hosts, and nothing orders them. Without this, a queue that + // comes up one second later leaves the controller permanently + // queue-less until someone restarts it — a boot-order race that + // presents as "status has been unavailable since Tuesday". + // + // It also composes with the callback above rather than fighting it: + // each background attempt is a connection attempt, so each one mints + // its own token instead of retrying a stale one. + .retry_on_initial_connect() + .connect(&url) + .await + .map_err(|source| Error::Connect { + url: url.clone(), + source, + })?; + + Ok(client) +} + +#[cfg(test)] +mod tests { + use super::*; + + /// The all-unset case is the common one — most hosts do not run the queue. + /// + /// Uses a prefix no deployment sets, so it cannot pass vacuously by + /// running inside a configured environment (the guard below covers the + /// same ground, and both are cheap). + #[test] + fn an_absent_environment_is_not_an_error() { + for k in [ + "SWARM_QUEUE_TEST_NATS_URL", + "SWARM_QUEUE_TEST_OIDC_TOKEN_ENDPOINT", + "SWARM_QUEUE_TEST_OIDC_CLIENT_ID", + "SWARM_QUEUE_TEST_OIDC_CLIENT_SECRET_FILE", + ] { + assert!(std::env::var(k).is_err(), "{k} must be unset for this test"); + } + assert!( + QueueConfig::from_env("SWARM_QUEUE_TEST") + .expect("absent is not an error") + .is_none() + ); + } + + /// The half-set case is the one the rule exists for: a deployment bug that + /// would otherwise look exactly like "no queue configured". + /// + /// SAFETY: single-threaded mutation of a process env var under a prefix no + /// other test or deployment uses; removed before returning. + #[test] + fn a_half_set_environment_is_a_hard_error() { + unsafe { + std::env::set_var("SWARM_QUEUE_HALF_NATS_URL", "nats://127.0.0.1:4222"); + } + let err = QueueConfig::from_env("SWARM_QUEUE_HALF") + .expect_err("a partial set must not read as absent"); + let msg = format!("{err}"); + assert!( + msg.contains("SWARM_QUEUE_HALF_OIDC_CLIENT_ID"), + "the error must name the missing variables, got: {msg}" + ); + unsafe { + std::env::remove_var("SWARM_QUEUE_HALF_NATS_URL"); + } + } +}