generic-mcp-server
by v4lheru
Verified
- src
- services
/**
* Base Service
*
* Abstract base class for all service implementations.
* Provides common functionality like rate limiting, error handling, and request management.
* Services that interact with external APIs should extend this class.
*/
import axios, { AxiosInstance, AxiosRequestConfig, AxiosResponse } from 'axios';
import config from '../config.js';
export abstract class BaseService {
protected client: AxiosInstance;
protected rateLimitRemaining: number = 100;
protected rateLimitReset: number = 0;
/**
* Creates a new service instance with the provided configuration
* @param baseURL - Base URL for API requests
* @param headers - Default headers to include with every request
*/
constructor(baseURL: string, headers: Record<string, string>) {
this.client = axios.create({
baseURL,
headers,
timeout: config.serviceTimeout
});
// Add response interceptor for rate limit handling
this.client.interceptors.response.use(
(response) => {
// Update rate limit info from headers if available
if (response.headers['x-ratelimit-remaining']) {
this.rateLimitRemaining = parseInt(response.headers['x-ratelimit-remaining']);
}
if (response.headers['x-ratelimit-reset']) {
this.rateLimitReset = parseInt(response.headers['x-ratelimit-reset']);
}
return response;
},
async (error) => {
// Handle rate limiting (429 Too Many Requests)
if (error.response?.status === 429) {
const resetTime = parseInt(error.response.headers['x-ratelimit-reset'] || '0');
const waitTime = Math.max(0, resetTime - Math.floor(Date.now() / 1000));
console.warn(`Rate limit exceeded. Waiting ${waitTime} seconds before retrying...`);
// Wait until rate limit resets
await new Promise(resolve => setTimeout(resolve, waitTime * 1000));
// Retry the request
return this.client.request(error.config);
}
// Handle other errors
this.handleRequestError(error);
throw error;
}
);
}
/**
* Checks if we're close to hitting rate limits and waits if necessary
* @protected
*/
protected async checkRateLimit(): Promise<void> {
if (this.rateLimitRemaining <= 5) { // Buffer of 5 requests
const now = Math.floor(Date.now() / 1000);
const waitTime = Math.max(0, this.rateLimitReset - now);
if (waitTime > 0) {
console.warn(`Approaching rate limit. Waiting ${waitTime} seconds...`);
await new Promise(resolve => setTimeout(resolve, waitTime * 1000));
}
}
}
/**
* Makes an API request with rate limit handling
* @protected
* @param requestFn - Function that makes the actual API request
* @returns The API response
*/
protected async makeRequest<T>(requestFn: () => Promise<T>): Promise<T> {
await this.checkRateLimit();
try {
return await requestFn();
} catch (error) {
this.handleRequestError(error);
throw error;
}
}
/**
* Handles request errors with appropriate logging and formatting
* @protected
* @param error - The error that occurred
*/
protected handleRequestError(error: any): void {
if (axios.isAxiosError(error)) {
const status = error.response?.status;
const data = error.response?.data;
const url = error.config?.url;
console.error(`API Error (${status}) for ${url}:`, data);
// Enhance error with more context
error.friendlyMessage = this.getFriendlyErrorMessage(error);
} else {
console.error('Non-Axios error:', error);
}
}
/**
* Creates a user-friendly error message based on the API error
* @protected
* @param error - The Axios error
* @returns A user-friendly error message
*/
protected getFriendlyErrorMessage(error: any): string {
if (!axios.isAxiosError(error)) {
return 'An unexpected error occurred';
}
const status = error.response?.status;
switch (status) {
case 400:
return 'The request was invalid. Please check your input.';
case 401:
return 'Authentication failed. Please check your API key.';
case 403:
return 'You do not have permission to access this resource.';
case 404:
return 'The requested resource was not found.';
case 429:
return 'Rate limit exceeded. Please try again later.';
case 500:
case 502:
case 503:
case 504:
return 'The server encountered an error. Please try again later.';
default:
return `An error occurred: ${error.message}`;
}
}
}