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Guard all metric registrations against re-evaluation

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Vite's dev server can re-evaluate modules, causing prom-client
"already registered" errors for all metrics, not just default ones.
Use getOrCreate pattern to reuse existing metrics from the registry.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ullrich Schäfer 2026-04-03 10:02:21 +01:00
parent a3ad073d96
commit d97992e967
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1 changed files with 33 additions and 21 deletions
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54
apps/planner/app/lib/metrics.server.ts
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@ -1,32 +1,44 @@
import client from "prom-client";
// Collect default Node.js metrics (event loop, heap, GC)
// Guard against duplicate registration during HMR
// Guard all metric registration — Vite's dev server can re-evaluate
// this module, causing "already registered" errors.
function getOrCreate<T>(name: string, create: () => T): T {
return (client.register.getSingleMetric(name) as T) ?? create();
}
if (!client.register.getSingleMetric("process_cpu_user_seconds_total")) {
client.collectDefaultMetrics();
}
export const httpRequestDuration = new client.Histogram({
name: "http_request_duration_seconds",
help: "Duration of HTTP requests in seconds",
labelNames: ["method", "route", "status"] as const,
buckets: [0.01, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5],
});
export const httpRequestDuration = getOrCreate("http_request_duration_seconds", () =>
new client.Histogram({
name: "http_request_duration_seconds",
help: "Duration of HTTP requests in seconds",
labelNames: ["method", "route", "status"] as const,
buckets: [0.01, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5],
}),
);
export const plannerActiveSessions = new client.Gauge({
name: "planner_active_sessions",
help: "Number of active planner sessions",
});
export const plannerActiveSessions = getOrCreate("planner_active_sessions", () =>
new client.Gauge({
name: "planner_active_sessions",
help: "Number of active planner sessions",
}),
);
export const plannerConnectedClients = new client.Gauge({
name: "planner_connected_clients",
help: "Number of connected WebSocket clients",
});
export const plannerConnectedClients = getOrCreate("planner_connected_clients", () =>
new client.Gauge({
name: "planner_connected_clients",
help: "Number of connected WebSocket clients",
}),
);
export const brouterRequestDuration = new client.Histogram({
name: "brouter_request_duration_seconds",
help: "Duration of BRouter API requests in seconds",
buckets: [0.1, 0.25, 0.5, 1, 2, 5, 10],
});
export const brouterRequestDuration = getOrCreate("brouter_request_duration_seconds", () =>
new client.Histogram({
name: "brouter_request_duration_seconds",
help: "Duration of BRouter API requests in seconds",
buckets: [0.1, 0.25, 0.5, 1, 2, 5, 10],
}),
);
export const registry = client.register;