Google API客户端(Python)：是否可以将BatchHttpRequest与ETag缓存一起使用

我正在使用YouTube数据API v3.

是否可以制作一个大的BatchHttpRequest(例如,参见here),并在httplib2级别使用ETag进行本地缓存(例如,参见here)？

ETag适用于单个查询,我不明白它们是否也适用于批处理请求.

解决方法:

TL; DR：

> BatchHttpRequest不能与缓存一起使用

这里是：

首先让我们看看初始化BatchHttpRequest的方法：

from apiclient.http import BatchHttpRequest

def list_animals(request_id, response, exception):
  if exception is not None:
    # Do something with the exception
    pass
  else:
    # Do something with the response
    pass

def list_farmers(request_id, response):
  """Do something with the farmers list response."""
  pass

service = build('farm', 'v2')

batch = service.new_batch_http_request()

batch.add(service.animals().list(), callback=list_animals)
batch.add(service.farmers().list(), callback=list_farmers)


batch.execute(http=http)

其次让我们看看如何使用ETag：

from google.appengine.api import memcache
http = httplib2.Http(cache=memcache)

现在让我们分析：

观察BatchHttpRequest示例的最后一行：batch.execute(http = http),现在检查source code是否执行,它调用_refresh_and_apply_credentials,它应用我们传递它的http对象.

def _refresh_and_apply_credentials(self, request, http):
    """Refresh the credentials and apply to the request.
    Args:
      request: HttpRequest, the request.
      http: httplib2.Http, the global http object for the batch.
    """
    # For the credentials to refresh, but only once per refresh_token
    # If there is no http per the request then refresh the http passed in
    # via execute()

这意味着,执行带有http的调用,可以传递给你创建的ETag http：

http = httplib2.Http(cache=memcache)
# This would mean we would get the ETags cached http
batch.execute(http=http)

更新1：

也可以尝试使用自定义对象：

from googleapiclient.discovery_cache import DISCOVERY_DOC_MAX_AGE
from googleapiclient.discovery_cache.base import Cache
from googleapiclient.discovery_cache.file_cache import Cache as FileCache

custCache = FileCache(max_age=DISCOVERY_DOC_MAX_AGE)
http = httplib2.Http(cache=custCache)
# This would mean we would get the ETags cached http
batch.execute(http=http)

因为,这只是对http2 lib中评论的预感：

"""If 'cache' is a string then it is used as a directory name for
        a disk cache. Otherwise it must be an object that supports the
        same interface as FileCache.

结论更新2：

在再次验证google-api-python源代码之后,我看到,BatchHttpRequest使用’POST’请求修复,并且内容类型为multipart / mixed; .. – source code.

给出一个事实的线索,BatchHttpRequest对POST数据很有用,然后将数据处理掉.

现在,记住这一点,观察httplib2请求方法使用的内容：_updateCache仅在满足以下条件时：

>请求在[“GET”,“HEAD”]或response.status == 303或是重定向请求
> ElSE – [200,203]中的response.status和[“GET”,“HEAD”]中的方法
> OR – 如果response.status == 304和method ==“GET”

这意味着,BatchHttpRequest不能与缓存一起使用.

标签：python,youtube-data-api,httplib2,google-api-client,youtube-data-api-v3
来源： https://codeday.me/bug/20190628/1311118.html