/**
* Unit tests for MetricsExporter
*
* Tests Prometheus metrics integration for monitoring:
* - Cache metrics (hits/misses)
* - HTTP metrics (requests, duration histogram)
* - Circuit breaker metrics (state gauge)
* - Connection pool metrics (active connections, queue depth)
*/
import { describe, it, expect, beforeEach, afterEach } from 'vitest';
import { MetricsExporter } from '../src/metrics-exporter';
describe('MetricsExporter', () => {
let metricsExporter: MetricsExporter;
beforeEach(() => {
metricsExporter = new MetricsExporter();
});
afterEach(() => {
// Clear all metrics between tests
metricsExporter.reset();
});
describe('T079: Prometheus metrics registration', () => {
it('should register cache hit counter', async () => {
metricsExporter.recordCacheHit('schema');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('cache_hits_total{cache_type="schema"}');
});
it('should register cache miss counter', async () => {
metricsExporter.recordCacheMiss('schema');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('cache_misses_total{cache_type="schema"}');
});
it('should register HTTP request counter with status and method labels', async () => {
metricsExporter.recordHttpRequest('POST', 200);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('http_requests_total{method="POST",status="200"}');
});
it('should register HTTP request duration histogram', async () => {
metricsExporter.recordHttpDuration('POST', '/mcp/tools', 0.15);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('http_request_duration_seconds');
});
it('should register circuit breaker state gauge', async () => {
metricsExporter.setCircuitBreakerState('filesystem', 'closed');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('circuit_breaker_state{server="filesystem"}');
});
it('should register pool active connections gauge', async () => {
metricsExporter.setPoolActiveConnections(5);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('pool_active_connections');
});
it('should register pool queue depth gauge', async () => {
metricsExporter.setPoolQueueDepth(10);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('pool_queue_depth');
});
it('should register pool queue wait histogram', async () => {
metricsExporter.recordPoolQueueWait(0.25);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('pool_queue_wait_seconds');
});
});
describe('T080: HTTP histogram buckets (web service optimized)', () => {
it('should use buckets: 0.01, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5 seconds', async () => {
const expectedBuckets = [0.01, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5];
// Record durations at each bucket boundary
expectedBuckets.forEach(duration => {
metricsExporter.recordHttpDuration('GET', '/health', duration);
});
const metrics = await metricsExporter.getMetrics();
// Verify all bucket boundaries appear in output
expectedBuckets.forEach(bucket => {
expect(metrics).toMatch(new RegExp(`le="${bucket}"`));
});
});
it('should include +Inf bucket for histogram', async () => {
metricsExporter.recordHttpDuration('GET', '/health', 10.5); // Above max bucket
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('le="+Inf"');
});
});
describe('T081: Metrics text format output (Prometheus exposition format)', () => {
it('should return Prometheus text format with HELP and TYPE', async () => {
metricsExporter.recordCacheHit('schema');
const metrics = await metricsExporter.getMetrics();
// Verify HELP line
expect(metrics).toMatch(/# HELP cache_hits_total/);
// Verify TYPE line
expect(metrics).toMatch(/# TYPE cache_hits_total counter/);
// Verify metric line with value
expect(metrics).toMatch(/cache_hits_total\{cache_type="schema"\} 1/);
});
it('should format histogram with _bucket, _sum, _count suffixes', async () => {
metricsExporter.recordHttpDuration('GET', '/health', 0.1);
const metrics = await metricsExporter.getMetrics();
// Histogram should have bucket suffixes
expect(metrics).toContain('http_request_duration_seconds_bucket');
// Histogram should have sum
expect(metrics).toContain('http_request_duration_seconds_sum');
// Histogram should have count
expect(metrics).toContain('http_request_duration_seconds_count');
});
it('should format gauge with current value', async () => {
metricsExporter.setPoolActiveConnections(7);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/pool_active_connections 7/);
});
it('should format counter with cumulative value', async () => {
metricsExporter.recordCacheHit('schema');
metricsExporter.recordCacheHit('schema');
metricsExporter.recordCacheHit('schema');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/cache_hits_total\{cache_type="schema"\} 3/);
});
});
describe('Cache metrics', () => {
it('should track cache hits with cache_type label', async () => {
metricsExporter.recordCacheHit('schema');
metricsExporter.recordCacheHit('schema');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/cache_hits_total\{cache_type="schema"\} 2/);
});
it('should track cache misses with cache_type label', async () => {
metricsExporter.recordCacheMiss('schema');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/cache_misses_total\{cache_type="schema"\} 1/);
});
it('should support multiple cache types', async () => {
metricsExporter.recordCacheHit('schema');
metricsExporter.recordCacheHit('redis');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('cache_type="schema"');
expect(metrics).toContain('cache_type="redis"');
});
});
describe('HTTP metrics', () => {
it('should track requests with method and status labels', async () => {
metricsExporter.recordHttpRequest('POST', 200);
metricsExporter.recordHttpRequest('POST', 200);
metricsExporter.recordHttpRequest('GET', 404);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/http_requests_total\{method="POST",status="200"\} 2/);
expect(metrics).toMatch(/http_requests_total\{method="GET",status="404"\} 1/);
});
it('should track request duration with method and endpoint labels', async () => {
metricsExporter.recordHttpDuration('GET', '/health', 0.05);
metricsExporter.recordHttpDuration('POST', '/mcp/tools', 0.15);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('method="GET"');
expect(metrics).toContain('endpoint="/health"');
expect(metrics).toContain('method="POST"');
expect(metrics).toContain('endpoint="/mcp/tools"');
});
});
describe('Circuit breaker metrics', () => {
it('should set circuit breaker state as gauge (0=closed, 1=open, 0.5=half-open)', async () => {
metricsExporter.setCircuitBreakerState('filesystem', 'closed');
let metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/circuit_breaker_state\{server="filesystem"\} 0/);
metricsExporter.setCircuitBreakerState('filesystem', 'open');
metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/circuit_breaker_state\{server="filesystem"\} 1/);
metricsExporter.setCircuitBreakerState('filesystem', 'half-open');
metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/circuit_breaker_state\{server="filesystem"\} 0\.5/);
});
it('should track multiple circuit breakers with server label', async () => {
metricsExporter.setCircuitBreakerState('filesystem', 'closed');
metricsExporter.setCircuitBreakerState('zen', 'open');
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('server="filesystem"');
expect(metrics).toContain('server="zen"');
});
});
describe('Connection pool metrics', () => {
it('should track active connections as gauge', async () => {
metricsExporter.setPoolActiveConnections(3);
let metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/pool_active_connections 3/);
metricsExporter.setPoolActiveConnections(5);
metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/pool_active_connections 5/);
});
it('should track queue depth as gauge', async () => {
metricsExporter.setPoolQueueDepth(15);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toMatch(/pool_queue_depth 15/);
});
it('should track queue wait time as histogram', async () => {
metricsExporter.recordPoolQueueWait(0.25);
metricsExporter.recordPoolQueueWait(0.8);
const metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('pool_queue_wait_seconds');
expect(metrics).toMatch(/pool_queue_wait_seconds_count 2/);
});
});
describe('Metrics endpoint integration', () => {
it('should return all metrics in single response', async () => {
// Record various metrics
metricsExporter.recordCacheHit('schema');
metricsExporter.recordHttpRequest('GET', 200);
metricsExporter.setCircuitBreakerState('filesystem', 'closed');
metricsExporter.setPoolActiveConnections(5);
const metrics = await metricsExporter.getMetrics();
// All metrics should be present in single output
expect(metrics).toContain('cache_hits_total');
expect(metrics).toContain('http_requests_total');
expect(metrics).toContain('circuit_breaker_state');
expect(metrics).toContain('pool_active_connections');
});
it('should be compatible with Prometheus scraper', async () => {
metricsExporter.recordHttpRequest('POST', 200);
const metrics = await metricsExporter.getMetrics();
// Verify Prometheus text format compliance
const lines = metrics.split('\n');
const hasHelp = lines.some(line => line.startsWith('# HELP'));
const hasType = lines.some(line => line.startsWith('# TYPE'));
const hasMetric = lines.some(line => !line.startsWith('#') && line.trim().length > 0);
expect(hasHelp).toBe(true);
expect(hasType).toBe(true);
expect(hasMetric).toBe(true);
});
});
describe('Reset functionality', () => {
it('should clear all metrics when reset', async () => {
metricsExporter.recordCacheHit('schema');
metricsExporter.recordHttpRequest('GET', 200);
metricsExporter.setCircuitBreakerState('filesystem', 'open');
// Verify metrics are set
let metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('cache_hits_total{cache_type="schema"} 1');
expect(metrics).toContain('http_requests_total{method="GET",status="200"} 1');
expect(metrics).toContain('circuit_breaker_state{server="filesystem"} 1');
metricsExporter.reset();
// After reset, only HELP and TYPE lines remain (labeled metrics don't appear until set)
metrics = await metricsExporter.getMetrics();
expect(metrics).toContain('# HELP cache_hits_total');
expect(metrics).toContain('# TYPE cache_hits_total counter');
// Labeled metrics don't appear until they're set again after reset
expect(metrics).not.toContain('cache_hits_total{cache_type="schema"}');
expect(metrics).not.toContain('http_requests_total{method="GET",status="200"}');
expect(metrics).not.toContain('circuit_breaker_state{server="filesystem"}');
});
});
});
