Struct merino_integration_tests::MetricsWatcher

pub struct MetricsWatcher {
    rx: Receiver<Vec<u8>>,
    messages: Vec<Message>,
}

Helper to collect metrics during tests, and make assertions about them.

Fields

rx: Receiver<Vec<u8>>

Crossbeam channel that receives metrics lines as bytes.

messages: Vec<Message>

Metrics received by the watcher from [rx].

Implementations

impl MetricsWatcher

pub fn new_with_client() -> (Self, StatsdClient)

Make a new metrics watcher, attach it to a StatsdClient and return both.

fn process_events(&mut self)

Consume any waiting events from rx and parse them as metrics.

pub fn all_messages(&mut self) -> &[Message]

Get a list of all the metrics seen by this watcher, primarily for debugging.

pub fn has<F>(&mut self, predicate: F) -> bool where
    F: FnMut(&Message) -> bool, 

Test if any metric this watcher received matches predicate.

Example

use statsd_parser::{Message, Metric, Counter};
metrics_client.incr("a-metric");

assert!(metrics_watcher.has(|msg| {
    println!("@@@ msg: {:?}", msg);
    msg.name == "a-metric"
        && matches!(msg.metric, Metric::Counter(Counter { value, .. }) if value == 1.0)
}));

pub fn has_histogram(&mut self, name: &str, expected_value: f64) -> bool

Test if any metric this watcher received was a histogram with the given name and value.

Values are compared by taking the absolute difference between them, and checking if it less than an epsilon of 0.0001.

pub fn has_incr(&mut self, name: &str) -> bool

Test if any metric this watcher increase in value for a given name.