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Refactor metrics data structures to use BTreeMap for ordered JSON output #19

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Merged
Brent-A merged 1 commit into from
Jan 31, 2026
Merged

Refactor metrics data structures to use BTreeMap for ordered JSON output #19

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4 changes: 2 additions & 2 deletions crates/mcsim-runner/src/metric_spec.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@
//! - `<breakdown>` is a label name to group by (node, node_type, group, packet_type)
//! - `*` as a breakdown means "break down by all available labels in the data"

use std::collections::HashMap;
use std::collections::{BTreeMap, HashMap};

/// Known breakdown labels that can be used for aggregation.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
Expand Down Expand Up @@ -385,7 +385,7 @@ pub struct MetricsExport {
/// Timestamp when metrics were collected.
pub timestamp: String,
/// All metrics with their values and breakdowns.
pub metrics: HashMap<String, MetricValue>,
pub metrics: BTreeMap<String, MetricValue>,
}

// ============================================================================
Expand Down
56 changes: 28 additions & 28 deletions crates/mcsim-runner/src/metrics_export.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ use crate::metric_spec::{
};
use metrics::{Counter, Gauge, Histogram, Key, KeyName, Metadata, Recorder, SharedString, Unit};
use parking_lot::RwLock;
use std::collections::HashMap;
use std::collections::BTreeMap;
use std::io::Write;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;
Expand All @@ -31,14 +31,14 @@ use std::sync::Arc;
#[derive(Debug, Default, Clone, serde::Serialize)]
pub struct NodeMetrics {
/// Counter metrics for this node.
#[serde(skip_serializing_if = "HashMap::is_empty")]
pub counters: HashMap<String, u64>,
#[serde(skip_serializing_if = "BTreeMap::is_empty")]
pub counters: BTreeMap<String, u64>,
/// Gauge metrics for this node.
#[serde(skip_serializing_if = "HashMap::is_empty")]
pub gauges: HashMap<String, f64>,
#[serde(skip_serializing_if = "BTreeMap::is_empty")]
pub gauges: BTreeMap<String, f64>,
/// Histogram metrics for this node.
#[serde(skip_serializing_if = "HashMap::is_empty")]
pub histograms: HashMap<String, HistogramSummary>,
#[serde(skip_serializing_if = "BTreeMap::is_empty")]
pub histograms: BTreeMap<String, HistogramSummary>,
}

/// Collected metric data for export.
Expand All @@ -47,14 +47,14 @@ pub struct MetricsSnapshot {
/// Timestamp when metrics were collected.
pub timestamp: String,
/// Counter metrics (name -> value) - aggregated across all nodes.
pub counters: HashMap<String, u64>,
pub counters: BTreeMap<String, u64>,
/// Gauge metrics (name -> value) - aggregated across all nodes.
pub gauges: HashMap<String, f64>,
pub gauges: BTreeMap<String, f64>,
/// Histogram metrics (name -> summary stats) - aggregated across all nodes.
pub histograms: HashMap<String, HistogramSummary>,
pub histograms: BTreeMap<String, HistogramSummary>,
/// Per-node breakdown of metrics.
#[serde(skip_serializing_if = "HashMap::is_empty")]
pub nodes: HashMap<String, NodeMetrics>,
#[serde(skip_serializing_if = "BTreeMap::is_empty")]
pub nodes: BTreeMap<String, NodeMetrics>,
}

/// Summary statistics for a histogram metric.
Expand Down Expand Up @@ -598,13 +598,13 @@ impl HistogramState {
#[derive(Debug, Default)]
struct RecorderState {
/// Counters keyed by full key string (metric name + labels).
counters: RwLock<HashMap<String, Arc<CounterState>>>,
counters: RwLock<BTreeMap<String, Arc<CounterState>>>,
/// Gauges keyed by full key string (metric name + labels).
gauges: RwLock<HashMap<String, Arc<GaugeState>>>,
gauges: RwLock<BTreeMap<String, Arc<GaugeState>>>,
/// Histograms keyed by full key string (metric name + labels).
histograms: RwLock<HashMap<String, Arc<HistogramState>>>,
histograms: RwLock<BTreeMap<String, Arc<HistogramState>>>,
/// Mapping from full key to (metric_name, labels) for breakdown.
key_metadata: RwLock<HashMap<String, KeyMetadata>>,
key_metadata: RwLock<BTreeMap<String, KeyMetadata>>,
/// Metric specs for label filtering. When set, only labels matching the
/// breakdown specifications will be stored, reducing memory usage.
label_specs: RwLock<Vec<MetricSpec>>,
Expand Down Expand Up @@ -929,10 +929,10 @@ impl RecorderState {
let metadata = self.key_metadata.read();

// Build aggregated metrics and per-node breakdown
let mut agg_counters: HashMap<String, u64> = HashMap::new();
let mut agg_gauges: HashMap<String, f64> = HashMap::new();
let mut agg_histograms: HashMap<String, Vec<f64>> = HashMap::new();
let mut nodes: HashMap<String, NodeMetrics> = HashMap::new();
let mut agg_counters: BTreeMap<String, u64> = BTreeMap::new();
let mut agg_gauges: BTreeMap<String, f64> = BTreeMap::new();
let mut agg_histograms: BTreeMap<String, Vec<f64>> = BTreeMap::new();
let mut nodes: BTreeMap<String, NodeMetrics> = BTreeMap::new();

// Process counters
for (key_str, counter) in self.counters.read().iter() {
Expand Down Expand Up @@ -983,7 +983,7 @@ impl RecorderState {
}

// Convert aggregated histogram samples to summaries
let histograms: HashMap<String, HistogramSummary> = agg_histograms
let histograms: BTreeMap<String, HistogramSummary> = agg_histograms
.into_iter()
.map(|(name, samples)| {
let summary = compute_histogram_summary(&samples);
Expand All @@ -1006,9 +1006,9 @@ impl RecorderState {
let metadata = self.key_metadata.read();

// Collect raw data keyed by (metric_name, labels)
let mut counter_data: HashMap<String, Vec<(KeyMetadata, u64)>> = HashMap::new();
let mut gauge_data: HashMap<String, Vec<(KeyMetadata, f64)>> = HashMap::new();
let mut histogram_data: HashMap<String, Vec<(KeyMetadata, Vec<f64>)>> = HashMap::new();
let mut counter_data: BTreeMap<String, Vec<(KeyMetadata, u64)>> = BTreeMap::new();
let mut gauge_data: BTreeMap<String, Vec<(KeyMetadata, f64)>> = BTreeMap::new();
let mut histogram_data: BTreeMap<String, Vec<(KeyMetadata, Vec<f64>)>> = BTreeMap::new();

// Collect counters
for (key_str, counter) in self.counters.read().iter() {
Expand Down Expand Up @@ -1041,7 +1041,7 @@ impl RecorderState {
}

// Build result based on specs
let mut metrics: HashMap<String, MetricValue> = HashMap::new();
let mut metrics: BTreeMap<String, MetricValue> = BTreeMap::new();

// Determine which metrics match which specs
let all_metric_names: std::collections::HashSet<_> = counter_data
Expand Down Expand Up @@ -1171,7 +1171,7 @@ fn apply_counter_breakdowns(
}

let label = breakdowns[depth];
let mut grouped: HashMap<String, Vec<(KeyMetadata, u64)>> = HashMap::new();
let mut grouped: BTreeMap<String, Vec<(KeyMetadata, u64)>> = BTreeMap::new();

for (meta, v) in data {
let keys = meta.breakdown_values(label);
Expand Down Expand Up @@ -1215,7 +1215,7 @@ fn apply_gauge_breakdowns(
}

let label = breakdowns[depth];
let mut grouped: HashMap<String, Vec<(KeyMetadata, f64)>> = HashMap::new();
let mut grouped: BTreeMap<String, Vec<(KeyMetadata, f64)>> = BTreeMap::new();

for (meta, v) in data {
let keys = meta.breakdown_values(label);
Expand Down Expand Up @@ -1261,7 +1261,7 @@ fn apply_histogram_breakdowns(
}

let label = breakdowns[depth];
let mut grouped: HashMap<String, Vec<(KeyMetadata, Vec<f64>)>> = HashMap::new();
let mut grouped: BTreeMap<String, Vec<(KeyMetadata, Vec<f64>)>> = BTreeMap::new();

for (meta, samples) in data {
let keys = meta.breakdown_values(label);
Expand Down