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问题：时间延迟是处理请求速率限制的好方法吗？

我对请求、API 和 Web 服务非常陌生。我正在尝试创建一个 Web 服务，给定一个 ID，向 MusicBrainz API 发出请求并检索一些信息。但是，显然我提出了太多的请求，或者太快了。在代码的最后一行，如果delay参数设置为0，就会出现这个错误：

{'error': 'Your requests are exceeding the allowable rate limit. Please see http://wiki.musicbrainz.org/XMLWebService for more information.'}

并查看该链接，我发现：

The rate at which your IP address is making requests is measured. If that rate is too high, all your requests will be declined (http 503) until the rate drops again. Currently that rate is (on average) 1 request per second.

因此我想，好吧，我将插入 1 秒的时间延迟，它会起作用。它奏效了，但我想有更好、更整洁、更聪明的方法来处理这样的问题。你认识一个吗？

代码：

####################################################
################### INSTRUCTIONS ###################
####################################################

'''
This script runs locally and returns a JSON formatted file, containing
information about the release-groups of an artist whose MBID must be provided.
'''

#########################################
############ CODE STARTS ################
#########################################


#IMPORT PACKAGES
#All of them come with Anaconda3 installation, otherwise they can be installed with pip 
import requests
import json
import math
import time


#Base URL for looking-up release-groups on musicbrainz.org
root_URL = 'http://musicbrainz.org/ws/2/'

#Parameters to run an example
offset = 10
limit = 1
MBID = '65f4f0c5-ef9e-490c-aee3-909e7ae6b2ab'



def collect_data(MBID, root_URL):

    '''
    Description: Auxiliar function to collect data from the MusicBrainz API

    Arguments: 
        MBID - MusicBrainz Identity of some artist.
        root_URL - MusicBrainz root_URL for requests

    Returns:
        decoded_output - dictionary file containing all the information about the release-groups 
        of type album of the requested artist
    '''

    #Joins paths. Note: Release-groups can be filtered by type.
    URL_complete = root_URL + 'release-group?artist=' + MBID + '&type=album' + '&fmt=json'

    #Creates a requests object and sends a GET request
    request = requests.get(URL_complete)

    assert request.status_code == 200

    output = request.content            #bits file 
    decoded_output = json.loads(output) #dict file

    return decoded_output 



def collect_releases(release_group_id, root_URL, delay = 1):

    '''
    Description: Auxiliar function to collect data from the MusicBrainz API

    Arguments: 
        release_group_id - ID of the release-group whose number of releases is to be extracted
        root_URL - MusicBrainz root_URL for requests

    Returns:
        releases_count - integer containing the number of releases of the release-group
    '''

    URL_complete = root_URL + 'release-group/' + release_group_id + '?inc=releases' + '&fmt=json'

    #Creates a requests object and sends a GET request
    request = requests.get(URL_complete)

    #Parses the content of the request to a dictionary
    output = request.content            
    decoded_output = json.loads(output) 

    #Time delay to not exceed MusicBrainz request rate limit
    time.sleep(delay)

    releases_count = 0

    if 'releases' in decoded_output:
        releases_count = len(decoded_output['releases'])
    else:
        print(decoded_output)
        #raise ValueError(decoded_output)


    return releases_count



def paginate(store_albums, offset, limit = 50):

    '''
    Description: Auxiliar function to paginate results

    Arguments: 
        store_albums - Dictionary containing information about each release-group
        offset - Integer. Corresponds to starting album to show.
        limit - Integer. Default to 50. Maximum number of albums to show per page

    Returns:
        albums_paginated - Paginated albums according to specified limit and offset
    '''

    #Restricts limit to 150 
    if limit > 150:
         limit = 150

    if offset > len(store_albums['albums']):
        raise ValueError('Offset is greater than number of albums')

    #Apply offset    
    albums_offset = store_albums['albums'][offset:]

    #Count pages
    pages = math.ceil(len(albums_offset) / limit)
    albums_limited = []

    if len(albums_offset) > limit:
        for i in range(pages):
            albums_limited.append(albums_offset[i * limit : (i+1) * limit])
    else:
        albums_limited = albums_offset

    albums_paginated = {'albums' : None}
    albums_paginated['albums'] = albums_limited


    return albums_paginated



def post(MBID, offset, limit, delay = 1):


    #Calls the auxiliar function 'collect_data' that retrieves the JSON file from MusicBrainz API
    json_file = collect_data(MBID, root_URL) 

    #Creates list and dictionary for storing the information about each release-group 
    album_details_list = []
    album_details = {"id": None, "title": None, "year": None, "release_count": None}

    #Loops through all release-groups in the JSON file 
    for item in json_file['release-groups']:

        album_details["id"]    = item["id"]
        album_details["title"] = item["title"]
        album_details["year"]  = item["first-release-date"].split("-")[0]
        album_details["release_count"] = collect_releases(item["id"], root_URL, delay)

        album_details_list.append(album_details.copy())   


    #Creates dictionary with all the albums of the artist    
    store_albums = {"albums": None}
    store_albums["albums"] = album_details_list

    #Paginates the dictionary 
    stored_paginated_albums = paginate(store_albums, offset , limit)

    #Returns JSON typed file containing the different albums arranged according to offset&limit
    return json.dumps(stored_paginated_albums)


#Runs the program and prints the JSON output as specified in the wording of the exercise 
print(post(MBID, offset, limit, delay = 1))
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1 回答 1

3

除了要求 API 所有者提高您的速率限制之外，没有更好的方法来处理这个问题。避免速率限制问题的唯一方法是一次不要发出太多请求，并且除了以绕过其请求计数器的方式入侵 API 之外，您还不得不在每个请求之间等待一秒钟。

于 2018-07-05T17:25:55.523 回答