在AWS Lambda中调用Yahoo Fantasy Sports API的令牌读取问题

问题背景 #

本地调用Yahoo Fantasy Sports API的OAuth2认证流程正常，但迁移到AWS Lambda后遇到两类异常：

问题1：从S3读取JSON内容传入OAuth2构造函数触发TypeError #

错误代码 #

s3x = boto3.client('s3')
o_bucket='mysportss3bucket'
o_path = 'oauth2.json'
resp = s3x.get_object(Bucket=o_bucket, Key = o_path)['Body'].read()
sc = OAuth2(None, None, resp)

报错信息 #

TypeError                                 Traceback (most recent call last)
<ipython-input-49-fd439f281ac6> in <module>
      1 print(resp)
----> 2 sc = OAuth2(None, None, resp)

TypeError: __init__() takes 3 positional arguments but 4 were given

原因与解决 #

Yahoo OAuth2的构造函数不支持直接将JSON字节作为位置参数传入，正确做法是先将字节内容转成UTF-8字符串，再通过from_string关键字参数传递：

s3x = boto3.client('s3')
o_bucket='mysportss3bucket'
o_path = 'oauth2.json'
# 读取字节并转成字符串
resp_str = s3x.get_object(Bucket=o_bucket, Key=o_path)['Body'].read().decode('utf-8')
# 使用关键字参数传入JSON字符串
sc = OAuth2(None, None, from_string=resp_str)

问题2：存放JSON文件到Lambda目录触发OSError #

报错信息 #

{
  "errorMessage": "[Errno 30] Read-only file system: 'tmp/oauth2.json'",
  "errorType": "OSError",
  "requestId": "7f23496c-50fa-4a49-b567-fd6bb66cabbc",
  "stackTrace": [
    "  File \"/var/task/lambda_function.py\", line 13, in lambda_handler\n    sc = OAuth2(None, None, from_file=x)\n",
    "  File \"/opt/python/lib/python3.9/site-packages/yahoo_oauth/oauth.py\", line 234, in __init__\n    super(OAuth2, self).__init__('oauth2', consumer_key, consumer_secret, **kwargs)\n",
    "  File \"/opt/python/lib/python3.9/site-packages/yahoo_oauth/oauth.py\", line 100, in __init__\n    write_data(data, vars(self).get('from_file', 'secrets.json'))\n",
    "  File \"/opt/python/lib/python3.9/site-packages/yahoo_oauth/utils.py\", line 41, in write_data\n    return func(data, filename)\n",
    "  File \"/opt/python/lib/python3.9/site-packages/yahoo_oauth/utils.py\", line 46, in json_write_data\n    with open(filename, 'w') as fp:\n"
  ]
}

原因与解决 #

1. 路径错误：Lambda唯一可写的临时目录是/tmp（开头带斜杠），而非tmp，需修正路径为/tmp/oauth2.json。
2. 权限限制：Lambda仅允许写入/tmp目录，确保文件存放路径符合要求。

修正后的代码示例（从S3下载文件到/tmp再读取）：

s3x = boto3.client('s3')
o_bucket='mysportss3bucket'
o_path = 'oauth2.json'
local_tmp_path = '/tmp/oauth2.json'
# 下载文件到Lambda可写目录
s3x.download_file(o_bucket, o_path, local_tmp_path)
# 从本地文件初始化OAuth2
sc = OAuth2(None, None, from_file=local_tmp_path)

内容的提问来源于stack exchange，提问作者rylaughlin