chore: update gateway pressure observability

frontend/src/utils/__tests__/prometheus.spec.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from 'vitest'
 import {
+  findMetricSamples,
   findMetricValueNumber,
   parsePrometheusSamples,
   sumMetricValues,
@@ -34,4 +35,15 @@ decision_remote_total{route_kind="responses",reason="remote_decision_miss"} 3
 
     expect(sumMetricValues(samples, 'decision_remote_total')).toBe(5)
   })
+
+  it('finds all matching samples by full or suffix metric name', () => {
+    const samples = parsePrometheusSamples(`
+aether_gateway_upstream_target_selected_total{target="openai"} 4
+aether_gateway_upstream_target_selected_total{target="azure"} 6
+aether_gateway_upstream_target_saturated_total{target="openai"} 1
+`)
+
+    expect(findMetricSamples(samples, 'upstream_target_selected_total')).toHaveLength(2)
+    expect(sumMetricValues(samples, 'upstream_target_selected_total')).toBe(10)
+  })
 })

frontend/src/utils/prometheus.ts

@@ -44,6 +44,13 @@ export function sumMetricValues(
   }, 0)
 }
 
+export function findMetricSamples(
+  samples: PrometheusSample[],
+  metricName: string
+): PrometheusSample[] {
+  return samples.filter(sample => metricNameMatches(sample.name, metricName))
+}
+
 function metricNameMatches(actual: string, expected: string): boolean {
   return actual === expected || actual.split('_').pop() === expected || actual.endsWith(`_${expected}`)
 }