b8c0a73e89
- 5.7: Enhanced structured logging with userId, productId, cacheHit, tokenCount - 5.8: Metrics module (counters + histograms) + /extract/metrics endpoint - 5.9: Grafana dashboard config for extraction-service (Loki queries) - 5.10: Error mapping — sidecar errors → proper HTTP status codes (408, 429, 502, 503) - 5.11: Circuit breaker for Python sidecar (5 failures → 30s OPEN) - 5.12: Graceful degradation — circuit open returns 503, cached results still served - 46 TS tests passing
86 lines
2.1 KiB
TypeScript
86 lines
2.1 KiB
TypeScript
/**
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* Simple circuit breaker for the Python sidecar.
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*
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* States: CLOSED (normal) → OPEN (fail fast) → HALF_OPEN (probe)
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* Opens after `failureThreshold` consecutive failures.
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* Resets after `resetTimeoutMs` in OPEN state.
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*/
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type State = 'CLOSED' | 'OPEN' | 'HALF_OPEN';
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export interface CircuitBreakerOptions {
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failureThreshold?: number;
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resetTimeoutMs?: number;
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}
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export class CircuitBreaker {
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private state: State = 'CLOSED';
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private failureCount = 0;
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private lastFailureTime = 0;
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private readonly failureThreshold: number;
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private readonly resetTimeoutMs: number;
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constructor(opts: CircuitBreakerOptions = {}) {
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this.failureThreshold = opts.failureThreshold ?? 5;
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this.resetTimeoutMs = opts.resetTimeoutMs ?? 30_000; // 30s
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}
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/**
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* Check if request is allowed. Throws if circuit is OPEN.
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*/
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allowRequest(): boolean {
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if (this.state === 'CLOSED') return true;
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if (this.state === 'OPEN') {
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// Check if reset timeout has elapsed
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if (Date.now() - this.lastFailureTime >= this.resetTimeoutMs) {
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this.state = 'HALF_OPEN';
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return true; // Allow one probe request
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}
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return false; // Still open, fail fast
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}
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// HALF_OPEN: allow the probe
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return true;
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}
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/**
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* Record a successful call — resets the breaker to CLOSED.
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*/
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recordSuccess(): void {
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this.failureCount = 0;
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this.state = 'CLOSED';
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}
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/**
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* Record a failure — may trip the breaker to OPEN.
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*/
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recordFailure(): void {
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this.failureCount++;
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this.lastFailureTime = Date.now();
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if (this.failureCount >= this.failureThreshold) {
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this.state = 'OPEN';
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}
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}
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get currentState(): State {
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return this.state;
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}
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get stats(): { state: State; failureCount: number; threshold: number; resetMs: number } {
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return {
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state: this.state,
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failureCount: this.failureCount,
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threshold: this.failureThreshold,
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resetMs: this.resetTimeoutMs,
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};
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}
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}
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// Module-level singleton for the sidecar circuit breaker
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export const sidecarBreaker = new CircuitBreaker({
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failureThreshold: 5,
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resetTimeoutMs: 30_000,
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});
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