lean_ctx/core/
proxy_metrics.rs

1// SPDX-License-Identifier: Apache-2.0
2//! Cross-process proxy request totals: the proxy process counts and
3//! persists them, `gain`, the dashboard and the context-overhead report read them.
4
5use std::sync::atomic::{AtomicU64, Ordering};
6
7use serde::{Deserialize, Serialize};
8
9static REQUESTS_TOTAL: AtomicU64 = AtomicU64::new(0);
10static TOKENS_SAVED_TOTAL: AtomicU64 = AtomicU64::new(0);
11static BYTES_COMPRESSED: AtomicU64 = AtomicU64::new(0);
12
13/// File holding the cross-process proxy totals. The proxy runs as its own
14/// (long-lived) process, so the only way the `gain` CLI / dashboard can learn
15/// how many provider turns actually carried the injected prefix is to read a
16/// persisted counter. This is what makes the net-of-injection figure honest.
17const PROXY_METRICS_FILE: &str = "proxy_metrics.json";
18
19/// Persist every Nth request. The body is tiny but we still avoid a write on
20/// every single request under high benchmark throughput; losing a few requests
21/// of accuracy between flushes is immaterial for a meter.
22const PERSIST_EVERY: u64 = 4;
23
24pub fn record_request(tokens_saved: u64, bytes_compressed: u64) {
25    let n = REQUESTS_TOTAL.fetch_add(1, Ordering::Relaxed) + 1;
26    TOKENS_SAVED_TOTAL.fetch_add(tokens_saved, Ordering::Relaxed);
27    BYTES_COMPRESSED.fetch_add(bytes_compressed, Ordering::Relaxed);
28    if n == 1 || n.is_multiple_of(PERSIST_EVERY) {
29        persist();
30    }
31}
32
33#[derive(Debug, Clone, Default, Serialize, Deserialize)]
34pub struct ProxyMetrics {
35    pub requests_total: u64,
36    pub tokens_saved_total: u64,
37    pub bytes_compressed: u64,
38}
39
40pub fn snapshot() -> ProxyMetrics {
41    ProxyMetrics {
42        requests_total: REQUESTS_TOTAL.load(Ordering::Relaxed),
43        tokens_saved_total: TOKENS_SAVED_TOTAL.load(Ordering::Relaxed),
44        bytes_compressed: BYTES_COMPRESSED.load(Ordering::Relaxed),
45    }
46}
47
48fn metrics_path() -> Option<std::path::PathBuf> {
49    crate::core::data_dir::lean_ctx_data_dir()
50        .ok()
51        .map(|d| d.join(PROXY_METRICS_FILE))
52}
53
54/// Atomically write the current in-process totals to disk. The proxy owns these
55/// totals for its lifetime, so a plain overwrite (not an additive merge) keeps
56/// the file in lock-step with the live atomics.
57pub fn persist() {
58    let Some(path) = metrics_path() else {
59        return;
60    };
61    let Ok(json) = serde_json::to_string(&snapshot()) else {
62        return;
63    };
64    let tmp = path.with_extension("json.tmp");
65    if std::fs::write(&tmp, json).is_ok() {
66        let _ = std::fs::rename(&tmp, &path);
67    }
68}
69
70/// Cross-process read of the persisted proxy totals, used by the `gain`
71/// CLI/dashboard to reconcile savings against the real number of provider turns.
72pub fn load_persisted() -> Option<ProxyMetrics> {
73    let path = metrics_path()?;
74    let data = std::fs::read_to_string(path).ok()?;
75    serde_json::from_str(&data).ok()
76}
lean_ctx/core/proxy_metrics.rs

lean_ctx/core/
proxy_metrics.rs
