Function prometheus_http_query::functions::label_join

pub fn label_join(
    vector: InstantVector, 
    dst_label: &str, 
    separator: &str, 
    src_labels: &[&str]
) -> Result<InstantVector, Error>

Apply the PromQL lable_join function.

use prometheus_http_query::{Client, Selector, InstantVector};
use prometheus_http_query::functions::label_join;
use std::convert::TryInto;

#[tokio::main(flavor = "current_thread")]
async fn main() -> Result<(), prometheus_http_query::Error> {
    let client = Client::default();
    let vector: InstantVector = Selector::new()
        .metric("up")
        .with("job", "prometheus")
        .try_into()?;

    let q = label_join(vector, "example_label", " on ", &["job", "instance"])?;

    let response = client.query(q, None, None).await?;
    let label = response.as_instant()
        .unwrap()
        .get(0)
        .unwrap()
        .metric()
        .get(&"example_label".to_string());

    assert_eq!(label, Some(&"prometheus on localhost:9090".to_string()));
    Ok(())
}