nm 0.1.30

Minimalistic high-performance metrics collection in highly concurrent environments
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105

use std::time::Duration;

use num_traits::AsPrimitive;

use crate::Magnitude;

/// Operations for observing the occurrences of an event.
///
/// This is implemented primarily by [`Event`][1] but also by [`ObservationBatch`][2],
/// thereby providing an abstraction for callers that wish to support both single and batch events.
///
/// [1]: crate::Event
/// [2]: crate::ObservationBatch
pub trait Observe {
    /// Observes an event that has no explicit magnitude.
    ///
    /// By convention, this is represented as a magnitude of 1. We expose a separate
    /// method for this to make it clear that the magnitude has no inherent meaning.
    ///
    /// # Example
    ///
    /// ```
    /// use nm::Event;
    ///
    /// thread_local! {
    ///     static REQUESTS: Event = Event::builder()
    ///         .name("requests")
    ///         .build();
    /// }
    ///
    /// // Count a single request occurrence
    /// REQUESTS.with(|event| event.observe_once());
    /// ```
    fn observe_once(&self);

    /// Observes an event with a specific magnitude.
    ///
    /// # Example
    ///
    /// ```
    /// use nm::Event;
    ///
    /// thread_local! {
    ///     static SENT_BYTES: Event = Event::builder()
    ///         .name("sent_bytes")
    ///         .build();
    /// }
    ///
    /// // Record sending 1024 bytes
    /// SENT_BYTES.with(|event| event.observe(1024));
    /// ```
    fn observe(&self, magnitude: impl AsPrimitive<Magnitude>);

    /// Observes an event with the magnitude being the indicated duration in milliseconds.
    ///
    /// Only the whole number part of the duration is used - fractional milliseconds are ignored.
    /// Values outside the i64 range are not guaranteed to be correctly represented.
    ///
    /// # Example
    ///
    /// ```
    /// use std::time::Duration;
    ///
    /// use nm::Event;
    ///
    /// thread_local! {
    ///     static REQUEST_DURATION: Event = Event::builder()
    ///         .name("request_duration_ms")
    ///         .build();
    /// }
    ///
    /// let duration = Duration::from_millis(250);
    /// REQUEST_DURATION.with(|event| event.observe_millis(duration));
    /// ```
    fn observe_millis(&self, duration: Duration);

    /// Observes the duration of a function call, in milliseconds.
    ///
    /// Uses a low-precision clock optimized for high-frequency capture. The measurement
    /// has a granularity of roughly 1-20 ms. Durations shorter than the granularity may
    /// appear as zero.
    ///
    /// # Example
    ///
    /// ```
    /// use nm::Event;
    ///
    /// thread_local! {
    ///     static DATABASE_QUERY_TIME: Event = Event::builder()
    ///         .name("database_query_time_ms")
    ///         .build();
    /// }
    ///
    /// fn query_database() -> String {
    /// #     // Simulated database query
    /// #     "result".to_string()
    /// }
    ///
    /// let result =
    ///     DATABASE_QUERY_TIME.with(|event| event.observe_duration_millis(|| query_database()));
    /// ```
    fn observe_duration_millis<F, R>(&self, f: F) -> R
    where
        F: FnOnce() -> R;
}