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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"DefaultCredentialsError (only sometimes) in Google Compute Engine with docker","articleBody":"Hello,\r\n\r\nI run a python script hourly, embedded in a docker container hosted on a Google Compute Engine instance. That script includes a step where I use python lib google.cloud.storage to upload files in google storage.\r\n\r\nI want to use the default service account of the compute engine instance. As written in the [doc](https://google-cloud-python.readthedocs.io/en/latest/google-cloud-auth.html), authentication should “just work”. And most of the time it does.\r\n\r\nYet I quite often get the error:\r\nFile \"/usr/local/lib/python2.7/dist-packages/google/auth/_default.py\", line 282, in default raise exceptions.DefaultCredentialsError(_HELP_MESSAGE)\r\ngoogle.auth.exceptions.DefaultCredentialsError: Could not automatically determine credentials. Please set GOOGLE_APPLICATION_CREDENTIALS or explicitly create credential and re-run the application. For more information, please see https://developers.google.com/accounts/docs/application-default-credentials.\r\n\r\nMy code:\r\n```\r\nimport google.auth\r\nfrom google.cloud import storage\r\n...\r\ncredentials, projectId = google.auth.default()\r\n# Next line raises sometimes the exception\r\nclient = storage.Client(projectId, credentials=credentials)\r\n...\r\n```\r\n\r\nWhen I run a python CLI from that same docker container, and call the `credentials, projectId = google.auth.default()`, I can see that the credentials are a `google.auth.compute_engine.credentials.Credentials object`, so I guess that the \"magic\" works even in a container (the doc does not explain how it works though).\r\n\r\nAny explanation on how to make it work, using the service account from the host compute instance ?\r\n\r\nMy env:\r\n* OS: ubuntu:16:04 (compute instance and docker instance)\r\n* python 2.7.12\r\n* google-cloud-storage==0.22.0, google-auth==0.5.0\r\n","author":{"url":"https://github.com/gjanvier","@type":"Person","name":"gjanvier"},"datePublished":"2017-02-10T09:11:44.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/2995/google-cloud-python/issues/2995"}