问题描述
我正在尝试从Cloud Function中访问Google云存储中文件上的自定义元数据，但它始终返回"None".
I'm trying to access the custom metadata on a file in Google cloud storage from within a Cloud Function, but it always returns "None".
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该文件上肯定有自定义元数据-可以从GCS浏览器中看到自定义元数据.
The file definitely has custom metadata on it - the custom metadata can be seen from the GCS browser.
如果我在云外壳环境中运行代码，则可以成功访问自定义元数据.
I can access the custom metadata successfully if I run my code in a cloud shell environment.
但是，如果我在云函数中运行相同的代码，则返回的blob.metadata始终为"None".
But if I run the same code in a cloud function, then the returned blob.metadata is always "None".
我做错了什么?与Cloud Shell相比，我在Cloud Function中必须做些什么.
What am I doing wrong? What do I have to do differently in a Cloud Function compared to a Cloud Shell.
from google.cloud import storage
client = storage.Client()
bucket = client.bucket(<my bucket name>)
blob = bucket.get_blob(<my filename>)
metadata = blob.metadata
还请注意，blob.download_as_string()可以正确获取文件内容-这只是我无法获取的自定义元数据.
Note also that blob.download_as_string() gets me the file contents correctly - it's just the custom metadata I can't get.
推荐答案
blob.metadata仅返回存储对象的 自定义元数据 (字典). None表示没有自定义元数据.请参见 metadata 的文档:
blob.metadata only returns Storage object's custom metadata (a dict). None means that there is no custom metadata. See the docs of metadata :
Object资源(API)的文档指定metadata为:
The documentation of Object resource (API) specify that metadata is :
请注意，自定义元数据与固定键元数据不同，您还可以使用Google Cloud Console中的编辑元数据按钮进行编辑.固定键元数据包含:
Note that custom metadata is different from fixed-key metadata, that you can also edit with Edit metadata button in Google Cloud Console. Fixed-key metadata contains :
- 内容类型
- 内容编码
- 内容处置
- 内容语言
- 缓存控制
可以通过blob.content_type，blob.content_encoding，...访问这种特殊类型的元数据(请检查完整示例).
This particular kind of metadata can be accessed via blob.content_type, blob.content_encoding, ... (check a complete example).
要添加自定义元数据，只需在同一窗口中单击添加项目按钮(编辑元数据)或使用gsutil(请参阅 编辑对象元数据文档 ):
To add custom metadata, just click Add item button on the same window (Edit metadata) or use gsutil (see Editing object metadata docs) :
gsutil setmeta -h "x-goog-meta-examplekey:examplevalue" gs://<your-bucket>
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