python - 谷歌 API 客户端(Python): is it possible to use BatchHttpRequest with ETag caching

Question

我使用的是 YouTube 数据 API v3。

是否有可能制作一个大的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 )？

ETags 对于单个查询工作得很好，我不知道它们是否对批量请求也有用。

Answer 1

长话短说:

• BatchHttpRequest 不能与缓存一起使用

在这里:

先看看BatchHttpRequest的初始化方式:

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)

现在让我们分析一下:

观察 BatchHttpRequest 示例的最后一行:batch.execute(http=http)，现在检查 source code对于执行，它调用 _refresh_and_apply_credentials，它应用我们传递给它的 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，接受 http 的执行调用可以传递给您创建的 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 库中注释的预感:

"""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:

再次验证 google-api-python 源代码后，我看到，BatchHttpRequest 已修复为 'POST' 请求，并且内容类型为 多部分/混合;.. - source code .

提供有关以下事实的线索，BatchHttpRequest 可用于POST 数据，然后在后面进行处理。

现在，牢记这一点，观察什么 httplib2 request 方法使用:_updateCache 仅当满足以下条件时:

1. 请求在 ["GET", "HEAD"] 或 response.status == 303 或者是 redirect request<
2. ElSE -- response.status in [200, 203] and method in ["GET", "HEAD"]
3. 或 -- if response.status == 304 and method == "GET"

这意味着，BatchHttpRequest 不能与缓存一起使用。