fix; HTTP/429 when requesting authors information, resolves #1570

server/providers/Audnexus.js

@@ -1,78 +1,123 @@
 const axios = require('axios')
 const { levenshteinDistance } = require('../utils/index')
 const Logger = require('../Logger')
+const { RateLimiter } = require('limiter');
 
 class Audnexus {
+  static _instance = null;
+
   constructor() {
+    // ensures Audnexus class is singleton 
+    if (Audnexus._instance) {
+      return Audnexus._instance
+    }
+
     this.baseUrl = 'https://api.audnex.us'
+
+    // @see https://github.com/laxamentumtech/audnexus#-deployment-
+    this.limiter = new RateLimiter({
+      tokensPerInterval: 100,
+      fireImmediately: true,
+      interval: 'minute',
+    })
+
+    Audnexus._instance = this
   }
 
   authorASINsRequest(name, region) {
     name = encodeURIComponent(name)
     const regionQuery = region ? `&region=${region}` : ''
     const authorRequestUrl = `${this.baseUrl}/authors?name=${name}${regionQuery}`
+
     Logger.info(`[Audnexus] Searching for author "${authorRequestUrl}"`)
-    return axios.get(authorRequestUrl).then((res) => {
-      return res.data || []
-    }).catch((error) => {
-      Logger.error(`[Audnexus] Author ASIN request failed for ${name}`, error)
-      return []
-    })
+
+    return this._processRequest(() => axios.get(authorRequestUrl))
+      .then((res) => res.data || [])
+      .catch((error) => {
+        Logger.error(`[Audnexus] Author ASIN request failed for ${name}`, error)
+        return []
+      })
   }
 
   authorRequest(asin, region) {
     asin = encodeURIComponent(asin)
     const regionQuery = region ? `?region=${region}` : ''
     const authorRequestUrl = `${this.baseUrl}/authors/${asin}${regionQuery}`
+
     Logger.info(`[Audnexus] Searching for author "${authorRequestUrl}"`)
-    return axios.get(authorRequestUrl).then((res) => {
-      return res.data
-    }).catch((error) => {
-      Logger.error(`[Audnexus] Author request failed for ${asin}`, error)
-      return null
-    })
+
+    return this._processRequest(() => axios.get(authorRequestUrl))
+      .then((res) => res.data)
+      .catch((error) => {
+        Logger.error(`[Audnexus] Author request failed for ${asin}`, error)
+        return null
+      })
+  }
+
+  /**
+   * @description Process a request with a rate limiter
+   * 
+   * @param {*} request 
+   * @returns 
+   */
+  async _processRequest(request) {
+    const remainingTokens = await this.limiter.removeTokens(1)
+    Logger.info(`[Audnexus] Attempting request with ${remainingTokens} remaining tokens and ${this.limiter.tokensThisInterval} this interval`)
+
+    if (remainingTokens >= 1) {
+      return request()
+    }
+
+    // 100 tokens(requests) per minute give a refresh of ~1.67 per second, 
+    // so a 10 second wait will yield ~16.7 additional tokens
+    Logger.info('[Audnexus] Sleeping for 10 seconds')
+    await new Promise(resolve => setTimeout(resolve, 10000))
+
+    return this._processRequest(request)
   }
 
   async findAuthorByASIN(asin, region) {
     const author = await this.authorRequest(asin, region)
-    if (!author) {
-      return null
-    }
-    return {
-      asin: author.asin,
-      description: author.description,
-      image: author.image || null,
-      name: author.name
-    }
+
+    return author ?
+      {
+        asin: author.asin,
+        description: author.description,
+        image: author.image || null,
+        name: author.name
+      } : null
   }
 
   async findAuthorByName(name, region, maxLevenshtein = 3) {
     Logger.debug(`[Audnexus] Looking up author by name ${name}`)
+
     const asins = await this.authorASINsRequest(name, region)
     const matchingAsin = asins.find(obj => levenshteinDistance(obj.name, name) <= maxLevenshtein)
+
     if (!matchingAsin) {
       return null
     }
+
     const author = await this.authorRequest(matchingAsin.asin)
-    if (!author) {
-      return null
-    }
-    return {
-      asin: author.asin,
-      description: author.description,
-      image: author.image || null,
-      name: author.name
-    }
+    return author ?
+      {
+        description: author.description,
+        image: author.image || null,
+        asin: author.asin,
+        name: author.name
+      } : null
   }
 
   getChaptersByASIN(asin, region) {
     Logger.debug(`[Audnexus] Get chapters for ASIN ${asin}/${region}`)
-    return axios.get(`${this.baseUrl}/books/${asin}/chapters?region=${region}`).then((res) => {
-      return res.data
-    }).catch((error) => {
-      Logger.error(`[Audnexus] Chapter ASIN request failed for ${asin}/${region}`, error)
-      return null
-    })
+
+    return this._processRequest(() => axios.get(`${this.baseUrl}/books/${asin}/chapters?region=${region}`))
+      .then((res) => res.data)
+      .catch((error) => {
+        Logger.error(`[Audnexus] Chapter ASIN request failed for ${asin}/${region}`, error)
+        return null
+      })
   }
 }
+
 module.exports = Audnexus