inspector-analysis 0.1.0

Deterministic diagnostic rules over Tokio runtime snapshots
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
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143

//! Snapshot comparison with explicit counter-reset and instrumentation-change handling.
use inspector_core::{CoreError, MetricKind, Observation, Snapshot, SnapshotDelta};

/// Compare two snapshots. Never invents data: `None` stays `None`.
/// Marks comparison unreliable on counter reset or completeness drift.
pub fn compare_snapshots(
    base: &Observation<Snapshot>,
    current: &Observation<Snapshot>,
) -> Result<SnapshotDelta, CoreError> {
    let mut notes = Vec::new();
    let mut unreliable = false;
    let mut reason: Option<String> = None;

    // Counter-reset detection.
    for b in &base.data.metrics {
        if let Some(c) = current.data.metrics.iter().find(|m| m.name == b.name) {
            if let (
                MetricKind::Counter {
                    total: bt,
                    reset_detected: _,
                },
                MetricKind::Counter {
                    total: ct,
                    reset_detected: _,
                },
            ) = (&b.kind, &c.kind)
            {
                if ct < bt {
                    unreliable = true;
                    reason = Some(format!("counter '{}' reset: {bt} -> {ct}", b.name));
                    notes.push(reason.clone().unwrap());
                }
            }
        }
    }

    // Instrumentation drift: different missing-field sets mean different visibility.
    if base.data.overview.metric_names != current.data.overview.metric_names
        || base.completeness.missing_fields != current.completeness.missing_fields
    {
        notes.push("instrumentation/visibility changed between snapshots".to_string());
    }

    let latency_delta_ratio = match (
        histogram_p50(&base.data, "request_latency_ms"),
        histogram_p50(&current.data, "request_latency_ms"),
    ) {
        (Some(b), Some(c)) if b > 0.0 => Some(c / b),
        _ => None, // missing is not zero
    };

    let task_growth = match (
        base.data.overview.active_tasks,
        current.data.overview.active_tasks,
    ) {
        (Some(b), Some(c)) => Some(c as i64 - b as i64),
        _ => None,
    };

    Ok(SnapshotDelta {
        base_id: base.observation_id.clone(),
        current_id: current.observation_id.clone(),
        latency_delta_ratio,
        task_growth,
        unreliable,
        reason,
        notes,
    })
}

fn histogram_p50(snap: &Snapshot, name: &str) -> Option<f64> {
    snap.metrics
        .iter()
        .find(|m| m.name == name)
        .and_then(|m| match &m.kind {
            MetricKind::Histogram { p50, .. } => *p50,
            MetricKind::Gauge { value } => Some(*value),
            MetricKind::Counter { total, .. } => Some(*total),
        })
}

#[cfg(test)]
mod tests {
    use super::*;
    use inspector_core::{Completeness, MetricObservation, RuntimeOverview, SourceId};

    fn snap(p50: Option<f64>, tasks: Option<u64>) -> Observation<Snapshot> {
        let metrics = p50
            .map(|p| {
                vec![MetricObservation {
                    name: "request_latency_ms".into(),
                    kind: MetricKind::Histogram {
                        count: 100,
                        sum: p * 100.0,
                        p50: Some(p),
                        p95: Some(p * 1.5),
                        p99: Some(p * 2.0),
                    },
                    unit: "ms".into(),
                    observed_at_unix_ms: 0,
                }]
            })
            .unwrap_or_default();
        Observation::new(
            SourceId {
                console_addr: "test".into(),
                service_name: None,
            },
            Some(5000),
            0,
            Snapshot {
                overview: RuntimeOverview {
                    service_name: None,
                    console_addr: "test".into(),
                    active_tasks: tasks,
                    completed_tasks: None,
                    tasks_truncated: false,
                    metric_names: vec!["request_latency_ms".into()],
                },
                tasks: vec![],
                resources: vec![],
                metrics,
            },
            Completeness::complete(),
        )
    }

    #[test]
    fn detects_regression_ratio() {
        let d =
            compare_snapshots(&snap(Some(40.0), Some(12)), &snap(Some(310.0), Some(142))).unwrap();
        assert!((d.latency_delta_ratio.unwrap() - 7.75).abs() < 0.01);
        assert_eq!(d.task_growth, Some(130));
        assert!(!d.unreliable);
    }

    #[test]
    fn missing_is_not_zero() {
        let d = compare_snapshots(&snap(None, None), &snap(Some(40.0), None)).unwrap();
        assert_eq!(d.latency_delta_ratio, None);
        assert_eq!(d.task_growth, None);
    }
}