Provide a UrlCredentialsProvider for assume role (#317)

Author: yanghua

tosfs/certification.py

@@ -14,10 +14,12 @@
 """It contains everything about certification via a file-based provider."""
 
 import threading
-from datetime import datetime
+from datetime import datetime, timedelta
 from typing import Optional
 from xml.etree import ElementTree
 
+import requests
+from tos.consts import ECS_DATE_FORMAT
 from tos.credential import Credentials, CredentialsProvider
 
 from tosfs.core import logger
@@ -182,3 +184,55 @@ def _try_get_credentials(self) -> Optional[Credentials]:
             )
             return None
         return self.credentials
+
+
+class UrlCredentialsProvider(CredentialsProvider):
+    """The class provides the credentials from an url."""
+
+    def __init__(self, credential_url: str):
+        """Initialize the UrlCredentialsProvider."""
+        if not credential_url:
+            raise TosfsCertificationError("The credential_url param must not be empty.")
+        self._lock = threading.Lock()
+        self.expires: Optional[datetime] = None
+        self.credentials = None
+        self.credential_url = credential_url
+
+    def get_credentials(self) -> Credentials:
+        """Get the credentials from the url."""
+        res = self._try_get_credentials()
+        if res is not None:
+            return res
+        with self._lock:
+            try:
+                res = self._try_get_credentials()
+                if res is not None:
+                    return res
+
+                res = requests.get(self.credential_url, timeout=30)
+                res_body = res.json()
+                self.credentials = Credentials(
+                    res_body.get("AccessKeyId"),
+                    res_body.get("SecretAccessKey"),
+                    res_body.get("SessionToken"),
+                )
+                self.expires = datetime.strptime(
+                    res_body.get("ExpiredTime"), ECS_DATE_FORMAT
+                )
+                return self.credentials
+            except Exception as e:
+                if self.expires is not None and (
+                    datetime.now().timestamp() < self.expires.timestamp()
+                ):
+                    return self.credentials
+                raise TosfsCertificationError("Get token failed") from e
+
+    def _try_get_credentials(self) -> Optional[Credentials]:
+        if self.expires is None or self.credentials is None:
+            return None
+        if (
+            datetime.now().timestamp()
+            > (self.expires - timedelta(minutes=10)).timestamp()
+        ):
+            return None
+        return self.credentials

tosfs/exceptions.py

@@ -13,19 +13,27 @@
 # limitations under the License.
 
 """It contains exceptions definition for the tosfs package."""
+from typing import Optional
 
 
 class TosfsError(Exception):
     """Base class for all tosfs exceptions."""
 
-    def __init__(self, message: str):
+    def __init__(self, msg: str, cause: Optional[Exception] = None):
         """Initialize the base class for all exceptions in the tosfs package."""
-        super().__init__(message)
+        super().__init__(msg, cause)
+        self.message = msg
+        self.cause = cause
+
+    def __str__(self) -> str:
+        """Return the string representation of the exception."""
+        error = {"message": self.message, "case": str(self.cause)}
+        return str(error)
 
 
 class TosfsCertificationError(TosfsError):
     """Exception class for certification related exception."""
 
-    def __init__(self, message: str):
+    def __init__(self, message: str, cause: Optional[Exception] = None):
         """Initialize the exception class for certification related exception."""
-        super().__init__(message)
+        super().__init__(message, cause)