@iota-big3/sdk-gateway/dist/packages/sdk-gateway/src/resilience/circuit-breaker.js

Universal API Gateway with protocol translation, intelligent routing, rate limiting, health checking, and caching

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.CircuitBreaker = void 0;
const events_1 = require("events");
class CircuitBreaker extends events_1.EventEmitter {
    constructor(config) {
        super();
        this.state = 'CLOSED';
        this.failures = 0;
        this.successes = 0;
        this.isEnabled = true;
        this.config = {
            ...config,
            failureThreshold: config.failureThreshold ?? 5,
            recoveryTimeout: config.recoveryTimeout ?? 30000,
            monitoringPeriod: config.monitoringPeriod ?? 60000
        };
    }
    async execute(fn) {
        if (!this.isEnabled) {
            return fn();
        }
        if (this.state === 'OPEN') {
            if (this.shouldAttemptReset()) {
                this.state = 'HALF_OPEN';
                this.emit('state:changed', { state: this.state, timestamp: Date.now() });
            }
            else {
                throw new Error('Circuit breaker is OPEN');
            }
        }
        try {
            const result = await fn();
            this.onSuccess();
            return result;
        }
        catch (error) {
            this.onFailure();
            throw error;
        }
    }
    onSuccess() {
        if (!this.isEnabled) {
            return;
        }
        this.successes++;
        if (this.state === 'HALF_OPEN') {
            this.reset();
        }
    }
    onFailure() {
        if (!this.isEnabled) {
            return;
        }
        this.failures++;
        this.lastFailure = Date.now();
        if (this.failures >= this.config.failureThreshold) {
            this.trip();
        }
    }
    shouldAttemptReset() {
        if (!this.nextAttempt) {
            return false;
        }
        return Date.now() >= this.nextAttempt;
    }
    trip() {
        if (!this.isEnabled) {
            return;
        }
        this.state = 'OPEN';
        this.nextAttempt = Date.now() + this.config.recoveryTimeout;
        this.emit('circuit:opened', {
            failures: this.failures,
            timestamp: Date.now()
        });
        this.emit('state:changed', {
            state: this.state,
            timestamp: Date.now()
        });
    }
    reset() {
        if (!this.isEnabled) {
            return;
        }
        this.state = 'CLOSED';
        this.failures = 0;
        this.successes = 0;
        this.lastFailure = undefined;
        this.nextAttempt = undefined;
        this.emit('circuit:closed', {
            timestamp: Date.now()
        });
        this.emit('state:changed', {
            state: this.state,
            timestamp: Date.now()
        });
    }
    getMetrics() {
        if (!this.isEnabled) {
            return {
                state: 'CLOSED',
                failures: 0,
                successes: 0
            };
        }
        return {
            state: this.state,
            failures: this.failures,
            successes: this.successes,
            lastFailure: this.lastFailure,
            nextAttempt: this.nextAttempt
        };
    }
    getState() {
        return this.state;
    }
    isCircuitOpen() {
        return this.state === 'OPEN';
    }
    isCircuitClosed() {
        return this.state === 'CLOSED';
    }
    isCircuitHalfOpen() {
        return this.state === 'HALF_OPEN';
    }
    enable() {
        this.isEnabled = true;
    }
    disable() {
        this.isEnabled = false;
    }
    forceOpen() {
        this.state = 'OPEN';
        this.nextAttempt = Date.now() + this.config.recoveryTimeout;
        this.emit('state:changed', { state: this.state, timestamp: Date.now() });
    }
    forceClose() {
        this.reset();
    }
    forceClear() {
        this.failures = 0;
        this.successes = 0;
        this.lastFailure = undefined;
        this.nextAttempt = undefined;
    }
}
exports.CircuitBreaker = CircuitBreaker;
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