运行Google Cloud Vision快速入门时遇google.auth.exceptions.TransportError错误

错误信息 #

ERROR:grpc._plugin_wrapping:AuthMetadataPluginCallback "<google.auth.transport.grpc.AuthMetadataPlugin object at 0x7fc1f3f66350>" raised exception!
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/dist-packages/google/auth/compute_engine/credentials.py", line 111, in refresh
    self._retrieve_info(request)
  File "/usr/local/lib/python3.7/dist-packages/google/auth/compute_engine/credentials.py", line 88, in _retrieve_info
    request, service_account=self._service_account_email
  File "/usr/local/lib/python3.7/dist-packages/google/auth/compute_engine/_metadata.py", line 234, in get_service_account_info
    return get(request, path, params={"recursive": "true"})
  File "/usr/local/lib/python3.7/dist-packages/google/auth/compute_engine/_metadata.py", line 187, in get
    response,
google.auth.exceptions.TransportError: ("Failed to retrieve http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/?recursive=true from the Google Compute Enginemetadata service. Status: 404 Response:\nb''", <google.auth.transport.requests._Response object at 0x7fc1fb046910>)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/dist-packages/grpc/_plugin_wrapping.py", line 90, in __call__
    context, _AuthMetadataPluginCallback(callback_state, callback))
  File "/usr/local/lib/python3.7/dist-packages/google/auth/transport/grpc.py", line 101, in __call__
    callback(self._get_authorization_headers(context), None)
  File "/usr/local/lib/python3.7/dist-packages/google/auth/transport/grpc.py", line 88, in _get_authorization_headers
    self._request, context.method_name, context.service_url, headers
  File "/usr/local/lib/python3.7/dist-packages/google/auth/credentials.py", line 133, in before_request
    self.refresh(request)
  File "/usr/local/lib/python3.7/dist-packages/google/auth/compute_engine/credentials.py", line 117, in refresh
    six.raise_from(new_exc, caught_exc)
  File "<string>", line 3, in raise_from
google.auth.exceptions.RefreshError: ("Failed to retrieve http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/?recursive=true from the Google Compute Enginemetadata service. Status: 404 Response:\nb''", <google.auth.transport.requests._Response object at 0x7fc1fb046910>)
---------------------------------------------------------------------------
_InactiveRpcError                         Traceback (most recent call last)
/usr/local/lib/python3.7/dist-packages/google/api_core/grpc_helpers.py in error_remapped_callable(*args, **kwargs)
     71         try:
---> 72             return callable_(*args, **kwargs)
     73         except grpc.RpcError as exc:

7 frames
_InactiveRpcError: <_InactiveRpcError of RPC that terminated with:
    status = StatusCode.UNAVAILABLE
    details = "Getting metadata from plugin failed with error: ("Failed to retrieve http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/?recursive=true from the Google Compute Enginemetadata service. Status: 404 Response:\nb''", <google.auth.transport.requests._Response object at 0x7fc1fb046910>)"
    debug_error_string = "UNKNOWN:Error received from peer vision.googleapis.com:443 {grpc_message:"Getting metadata from plugin failed with error: (\"Failed to retrieve http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/?recursive=true from the Google Compute Enginemetadata service. Status: 404 Response:\\nb''\\", <google.auth.transport.requests._Response object at 0x7fc1fb046910>)", grpc_status:14, created_time:"2022-09-13T14:48:30.187999422+00:00"}"
>

The above exception was the direct cause of the following exception:

ServiceUnavailable                        Traceback (most recent call last)
/usr/local/lib/python3.7/dist-packages/google/api_core/grpc_helpers.py in error_remapped_callable(*args, **kwargs)
     72             return callable_(*args, **kwargs)
     73         except grpc.RpcError as exc:
---> 74             raise exceptions.from_grpc_error(exc) from exc
     75 
     76     return error_remapped_callable

ServiceUnavailable: 503 Getting metadata from plugin failed with error: ("Failed to retrieve http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/?recursive=true from the Google Compute Enginemetadata service. Status: 404 Response:\nb''", <google.auth.transport.requests._Response object at 0x7fc1fb046910>)

执行代码 #

#connect to google drive
from google.colab import drive
drive.mount('/content/drive')

#download and extract google cloud client
!curl -O https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/google-cloud-cli-401.0.0-linux-x86_64.tar.gz
!tar -xf google-cloud-cli-401.0.0-linux-x86_64.tar.gz

#set credentials environment variable
!export GOOGLE_APPLICATION_CREDENTIALS=/content/drive/MyDrive/imagelabeling-1663076432940-26cfebd304cf.json

#install and init google cloud
!./google-cloud-sdk/install.sh --usage-reporting False --quiet
!./google-cloud-sdk/bin/gcloud init

#install google-cloud-vision libraries
!pip install --upgrade google-cloud-vision

#download cat image
!wget https://raw.githubusercontent.com/googleapis/python-vision/master/samples/snippets/quickstart/resources/wakeupcat.jpg

#run labeling code
import io
import os

# Imports the Google Cloud client library
from google.cloud import vision

# Instantiates a client
client = vision.ImageAnnotatorClient()

# The name of the image file to annotate
file_name = os.path.abspath('/content/wakeupcat.jpg')

# Loads the image into memory
with io.open(file_name, 'rb') as image_file:
    content = image_file.read()

image = vision.Image(content=content)

# Performs label detection on the image file
response = client.label_detection(image=image)
labels = response.label_annotations

print('Labels:')
for label in labels:
    print(label.description)

已完成的操作 #

• 执行gcloud init时选择重新初始化默认配置，通过网页登录谷歌账号并选择对应测试项目
• 测试项目已启用计费和Vision API
• 创建了拥有Owner角色的服务账号，并生成JSON密钥文件，已挂载到Colab的Drive路径中

问题原因及修复方案 #

错误核心是**GOOGLE_APPLICATION_CREDENTIALS环境变量未在Python运行环境中生效**——用!export设置的变量只作用于当前shell进程，不会传递到后续执行Python代码的进程，导致Vision客户端尝试从Colab元数据服务获取认证信息（Colab环境无默认服务账号元数据），从而抛出404错误。

修复步骤 #

1. 替换环境变量设置方式
   用Python的os.environ直接设置变量，确保能被Vision客户端读取。把原来的!export GOOGLE_APPLICATION_CREDENTIALS=...替换为：

   import os
   os.environ['GOOGLE_APPLICATION_CREDENTIALS'] = '/content/drive/MyDrive/imagelabeling-1663076432940-26cfebd304cf.json'
   

   这段代码必须放在from google.cloud import vision之前执行。

2. 可选：简化gcloud操作
   Colab预装了gcloud CLI，无需手动下载安装。可以去掉下载、解压gcloud的步骤，改用服务账号直接激活：

   !gcloud auth activate-service-account --key-file=/content/drive/MyDrive/imagelabeling-1663076432940-26cfebd304cf.json
   !gcloud config set project 你的项目ID
   

修改后的完整代码 #

from google.colab import drive
drive.mount('/content/drive')

# 设置环境变量（关键修复）
import os
os.environ['GOOGLE_APPLICATION_CREDENTIALS'] = '/content/drive/MyDrive/imagelabeling-1663076432940-26cfebd304cf.json'

# 验证环境变量路径
print("Credentials path:", os.environ.get('GOOGLE_APPLICATION_CREDENTIALS'))

# 安装依赖
!pip install --upgrade google-cloud-vision

# 下载测试图片
!wget https://raw.githubusercontent.com/googleapis/python-vision/master/samples/snippets/quickstart/resources/wakeupcat.jpg

# 调用Vision API
import io
from google.cloud import vision

client = vision.ImageAnnotatorClient()

file_name = os.path.abspath('/content/wakeupcat.jpg')
with io.open(file_name, 'rb') as image_file:
    content = image_file.read()

image = vision.Image(content=content)
response = client.label_detection(image=image)
labels = response.label_annotations

print('Labels:')
for label in labels:
    print(label.description)

内容的提问来源于stack exchange，提问作者matthias_buehlmann