feat(cache): external API cache (#786)

server/api/externalapi.ts

@@ -0,0 +1,106 @@
+import axios, { AxiosInstance, AxiosRequestConfig } from 'axios';
+import NodeCache from 'node-cache';
+import logger from '../logger';
+
+// 5 minute default TTL (in seconds)
+const DEFAULT_TTL = 300;
+
+// 10 seconds default rolling buffer (in ms)
+const DEFAULT_ROLLING_BUFFER = 10000;
+
+interface ExternalAPIOptions {
+  nodeCache?: NodeCache;
+  headers?: Record<string, unknown>;
+}
+
+class ExternalAPI {
+  protected axios: AxiosInstance;
+  private baseUrl: string;
+  private cache?: NodeCache;
+
+  constructor(
+    baseUrl: string,
+    params: Record<string, unknown>,
+    options: ExternalAPIOptions = {}
+  ) {
+    this.axios = axios.create({
+      baseURL: baseUrl,
+      params,
+      headers: {
+        'Content-Type': 'application/json',
+        Accept: 'application/json',
+        ...options.headers,
+      },
+    });
+    this.baseUrl = baseUrl;
+    this.cache = options.nodeCache;
+  }
+
+  protected async get<T>(
+    endpoint: string,
+    config?: AxiosRequestConfig,
+    ttl?: number
+  ): Promise<T> {
+    const cacheKey = this.serializeCacheKey(endpoint, config?.params);
+    const cachedItem = this.cache?.get<T>(cacheKey);
+    if (cachedItem) {
+      return cachedItem;
+    }
+
+    const response = await this.axios.get<T>(endpoint, config);
+
+    if (this.cache) {
+      this.cache.set(cacheKey, response.data, ttl ?? DEFAULT_TTL);
+    }
+
+    return response.data;
+  }
+
+  protected async getRolling<T>(
+    endpoint: string,
+    config?: AxiosRequestConfig,
+    ttl?: number
+  ): Promise<T> {
+    const cacheKey = this.serializeCacheKey(endpoint, config?.params);
+    const cachedItem = this.cache?.get<T>(cacheKey);
+
+    if (cachedItem) {
+      const keyTtl = this.cache?.getTtl(cacheKey) ?? 0;
+      logger.debug(`Loaded item from cache: ${cacheKey}`, {
+        keyTtl,
+      });
+
+      // If the item has passed our rolling check, fetch again in background
+      if (
+        keyTtl - (ttl ?? DEFAULT_TTL) * 1000 <
+        Date.now() - DEFAULT_ROLLING_BUFFER
+      ) {
+        this.axios.get<T>(endpoint, config).then((response) => {
+          this.cache?.set(cacheKey, response.data, ttl ?? DEFAULT_TTL);
+        });
+      }
+      return cachedItem;
+    }
+
+    const response = await this.axios.get<T>(endpoint, config);
+
+    if (this.cache) {
+      this.cache.set(cacheKey, response.data, ttl ?? DEFAULT_TTL);
+    }
+
+    return response.data;
+  }
+
+  private serializeCacheKey(
+    endpoint: string,
+    params?: Record<string, unknown>
+  ) {
+    if (!params) {
+      return `${this.baseUrl}${endpoint}`;
+    }
+
+    return `${this.baseUrl}${endpoint}${JSON.stringify(params)}`;
+  }
+}
+
+export default ExternalAPI;