reth_bench/bench/
metrics_scraper.rs

1//! Prometheus metrics scraper for reth-bench.
2//!
3//! Scrapes a node's Prometheus metrics endpoint after each block to record
4//! execution and state root durations with block-level granularity.
5
6use csv::Writer;
7use eyre::Context;
8use reqwest::Client;
9use serde::Serialize;
10use std::{path::Path, time::Duration};
11use tracing::info;
12
13/// Suffix for the metrics CSV output file.
14pub(crate) const METRICS_OUTPUT_SUFFIX: &str = "metrics.csv";
15
16/// A single row of scraped prometheus metrics for one block.
17#[derive(Debug, Clone, Serialize)]
18pub(crate) struct MetricsRow {
19    /// The block number.
20    pub(crate) block_number: u64,
21    /// EVM execution duration in seconds (from `sync_execution_execution_duration` gauge).
22    pub(crate) execution_duration_secs: Option<f64>,
23    /// State root computation duration in seconds (from
24    /// `sync_block_validation_state_root_duration` gauge).
25    pub(crate) state_root_duration_secs: Option<f64>,
26}
27
28/// Scrapes a Prometheus metrics endpoint after each block to collect
29/// execution and state root durations.
30pub(crate) struct MetricsScraper {
31    /// The full URL of the Prometheus metrics endpoint.
32    url: String,
33    /// Reusable HTTP client.
34    client: Client,
35    /// Collected metrics rows, one per block.
36    rows: Vec<MetricsRow>,
37}
38
39impl MetricsScraper {
40    /// Creates a new scraper if a URL is provided.
41    pub(crate) fn maybe_new(url: Option<String>) -> Option<Self> {
42        url.map(|url| {
43            info!(target: "reth-bench", %url, "Prometheus metrics scraping enabled");
44            let client = Client::builder()
45                .timeout(Duration::from_secs(5))
46                .build()
47                .expect("failed to build reqwest client");
48            Self { url, client, rows: Vec::new() }
49        })
50    }
51
52    /// Scrapes the metrics endpoint and records values for the given block.
53    pub(crate) async fn scrape_after_block(&mut self, block_number: u64) -> eyre::Result<()> {
54        let text = self
55            .client
56            .get(&self.url)
57            .send()
58            .await
59            .wrap_err("failed to fetch metrics endpoint")?
60            .error_for_status()
61            .wrap_err("metrics endpoint returned error status")?
62            .text()
63            .await
64            .wrap_err("failed to read metrics response body")?;
65
66        let execution = parse_gauge(&text, "sync_execution_execution_duration");
67        let state_root = parse_gauge(&text, "sync_block_validation_state_root_duration");
68
69        self.rows.push(MetricsRow {
70            block_number,
71            execution_duration_secs: execution,
72            state_root_duration_secs: state_root,
73        });
74        Ok(())
75    }
76
77    /// Writes collected metrics to a CSV file in the output directory.
78    pub(crate) fn write_csv(&self, output_dir: &Path) -> eyre::Result<()> {
79        let path = output_dir.join(METRICS_OUTPUT_SUFFIX);
80        info!(target: "reth-bench", "Writing scraped metrics to file: {:?}", path);
81        let mut writer = Writer::from_path(&path)?;
82        for row in &self.rows {
83            writer.serialize(row)?;
84        }
85        writer.flush()?;
86        Ok(())
87    }
88}
89
90/// Parses a Prometheus gauge value from exposition-format text.
91///
92/// Searches for lines starting with `name` followed by either a space or `{`
93/// (for labeled metrics), then parses the numeric value. Returns the last
94/// matching sample to handle metrics emitted with multiple label sets.
95fn parse_gauge(text: &str, name: &str) -> Option<f64> {
96    let mut result = None;
97    for line in text.lines() {
98        let line = line.trim();
99        if line.is_empty() || line.starts_with('#') {
100            continue;
101        }
102
103        if !line.starts_with(name) {
104            continue;
105        }
106
107        // Ensure we match the full metric name, not a prefix of another metric.
108        let rest = &line[name.len()..];
109        if !rest.starts_with(' ') && !rest.starts_with('{') {
110            continue;
111        }
112
113        // Format: `metric_name{labels} value [timestamp]` or `metric_name value [timestamp]`
114        // Value is always the second whitespace-separated token.
115        let mut parts = line.split_whitespace();
116        if let Some(value_str) = parts.nth(1) &&
117            let Ok(v) = value_str.parse::<f64>()
118        {
119            result = Some(v);
120        }
121    }
122    result
123}
124
125#[cfg(test)]
126mod tests {
127    use super::*;
128
129    #[test]
130    fn test_parse_gauge_simple() {
131        let text = r#"# HELP sync_execution_execution_duration Duration of execution
132# TYPE sync_execution_execution_duration gauge
133sync_execution_execution_duration 0.123456
134"#;
135        assert_eq!(parse_gauge(text, "sync_execution_execution_duration"), Some(0.123456));
136    }
137
138    #[test]
139    fn test_parse_gauge_missing() {
140        let text = "some_other_metric 1.0\n";
141        assert_eq!(parse_gauge(text, "sync_execution_execution_duration"), None);
142    }
143
144    #[test]
145    fn test_parse_gauge_with_labels() {
146        let text = "sync_block_validation_state_root_duration{instance=\"node1\"} 0.5\n";
147        assert_eq!(parse_gauge(text, "sync_block_validation_state_root_duration"), Some(0.5));
148    }
149
150    #[test]
151    fn test_parse_gauge_prefix_no_false_match() {
152        let text =
153            "sync_execution_execution_duration_total 99.0\nsync_execution_execution_duration 0.5\n";
154        assert_eq!(parse_gauge(text, "sync_execution_execution_duration"), Some(0.5));
155    }
156}
reth_bench/bench/metrics_scraper.rs

reth_bench/bench/
metrics_scraper.rs
