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//! X-Ray daemon client.
use std::env;
use std::net::{SocketAddr, UdpSocket};
use std::sync::Arc;
use serde::Serialize;
use crate::error::{Error, Result};
/// X-Ray client interface.
pub trait Client: Clone + std::fmt::Debug + Send + Sync {
/// Sends a segment to the xray daemon this client is connected to.
fn send<S>(&self, data: &S) -> Result<()>
where
S: Serialize;
}
/// X-Ray daemon client.
#[derive(Clone, Debug)]
pub struct DaemonClient {
socket: Arc<UdpSocket>,
}
impl DaemonClient {
const HEADER: &'static [u8] = br#"{"format": "json", "version": 1}"#;
const DELIMITER: &'static [u8] = &[b'\n'];
/// Return a new X-Ray client connected
/// to the provided `addr`
pub fn new(addr: SocketAddr) -> Result<Self> {
let socket = Arc::new(UdpSocket::bind(&[([0, 0, 0, 0], 0).into()][..])?);
socket.set_nonblocking(true)?;
socket.connect(addr)?;
Ok(DaemonClient { socket })
}
/// Creates a new X-Ray client from the Lambda environment variable.
///
/// The following environment variable must be set:
/// - `AWS_XRAY_DAEMON_ADDRESS`: X-Ray daemon address
///
/// Please refer to the [AWS documentation](https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html#configuration-envvars-runtime)
/// for more details.
pub fn from_lambda_env() -> Result<Self> {
let addr: SocketAddr = env::var("AWS_XRAY_DAEMON_ADDRESS")
.map_err(|_| Error::MissingEnvVar("AWS_XRAY_DAEMON_ADDRESS"))?
.parse::<SocketAddr>()
.map_err(|e| Error::BadConfig(format!("invalid X-Ray daemon address: {e}")))?;
DaemonClient::new(addr)
}
#[inline]
fn packet<S>(data: S) -> Result<Vec<u8>>
where
S: Serialize,
{
let bytes = serde_json::to_vec(&data)?;
Ok([Self::HEADER, Self::DELIMITER, &bytes].concat())
}
}
impl Client for DaemonClient {
fn send<S>(&self, data: &S) -> Result<()>
where
S: Serialize,
{
self.socket.send(&Self::packet(data)?)?;
Ok(())
}
}
/// Infallible client.
#[derive(Clone, Debug)]
pub enum InfallibleClient<C> {
/// Operational client.
Op(C),
/// Non-operational client.
Noop,
}
impl<C> InfallibleClient<C> {
/// Creates a new infallible client from a result of client creation.
pub fn new<E>(result: std::result::Result<C, E>) -> Self {
match result {
Ok(client) => Self::Op(client),
Err(_) => Self::Noop,
}
}
}
impl<C> Client for InfallibleClient<C>
where
C: Client,
{
fn send<S>(&self, data: &S) -> Result<()>
where
S: Serialize,
{
match self {
Self::Op(client) => client.send(data),
Self::Noop => Ok(()),
}
}
}
/// Conversion into an [`InfallibleClient`].
///
/// This is useful if you want to fall back to a "no-op" client if the creation
/// of a client fails.
///
/// ```
/// use xray_lite::{
/// Context as _,
/// CustomNamespace,
/// DaemonClient,
/// IntoInfallibleClient as _,
/// SubsegmentContext,
/// };
///
/// let client = DaemonClient::from_lambda_env().into_infallible();
/// # std::env::set_var("_X_AMZN_TRACE_ID", "Root=1-5759e988-bd862e3fe1be46a994272793;Parent=53995c3f42cd8ad8;Sampled=1");
/// let context = SubsegmentContext::from_lambda_env(client).unwrap();
/// let _session = context.enter_subsegment(CustomNamespace::new("readme.example"));
/// ```
pub trait IntoInfallibleClient {
/// Client type.
type Client: Client;
/// Converts a value into an [`InfallibleClient`].
fn into_infallible(self) -> InfallibleClient<Self::Client>;
}
impl<C> IntoInfallibleClient for std::result::Result<C, Error>
where
C: Client,
{
type Client = C;
fn into_infallible(self) -> InfallibleClient<C> {
InfallibleClient::new(self)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn client_prefixes_packets_with_header() {
assert_eq!(
DaemonClient::packet(serde_json::json!({
"foo": "bar"
}))
.unwrap(),
[
br#"{"format": "json", "version": 1}"# as &[u8],
&[b'\n'],
br#"{"foo":"bar"}"#,
]
.concat()
)
}
}