feat(streaming): add new s3 streaming utility

.github/boring-cyborg.yml

@@ -42,6 +42,8 @@ labelPRBasedOnFilePath:
   typing:
     - aws_lambda_powertools/utilities/typing/*
     - mypy.ini
+  streaming:
+    - aws_lambda_powertools/utilities/streaming/*
   commons:
     - aws_lambda_powertools/shared/*
 

README.md

@@ -15,7 +15,6 @@ A suite of Python utilities for AWS Lambda functions to ease adopting best pract
 
 ![hero-image](https://user-images.githubusercontent.com/3340292/198254617-d0fdb672-86a6-4988-8a40-adf437135e0a.png)
 
-
 ## Features
 
 * **[Tracing](https://awslabs.github.io/aws-lambda-powertools-python/latest/core/tracer/)** - Decorators and utilities to trace Lambda function handlers, and both synchronous and asynchronous functions
@@ -32,6 +31,7 @@ A suite of Python utilities for AWS Lambda functions to ease adopting best pract
 * **[Parser](https://awslabs.github.io/aws-lambda-powertools-python/latest/utilities/parser/)** - Data parsing and deep validation using Pydantic
 * **[Idempotency](https://awslabs.github.io/aws-lambda-powertools-python/latest/utilities/idempotency/)** - Convert your Lambda functions into idempotent operations which are safe to retry
 * **[Feature Flags](https://awslabs.github.io/aws-lambda-powertools-python/latest/utilities/feature_flags/)** - A simple rule engine to evaluate when one or multiple features should be enabled depending on the input
+* **[Streaming](https://awslabs.github.io/aws-lambda-powertools-python/latest/utilities/streaming/)** - Streams datasets larger than the available memory as streaming data.
 
 ### Installation
 

aws_lambda_powertools/utilities/streaming/__init__.py

@@ -0,0 +1,3 @@
+from aws_lambda_powertools.utilities.streaming.s3_object import S3Object
+
+__all__ = ["S3Object"]

aws_lambda_powertools/utilities/streaming/_s3_seekable_io.py

@@ -0,0 +1,184 @@
+import io
+import logging
+from typing import IO, TYPE_CHECKING, AnyStr, Iterable, List, Optional
+
+import boto3
+
+from aws_lambda_powertools.utilities.streaming.compat import PowertoolsStreamingBody
+
+if TYPE_CHECKING:
+    from mypy_boto3_s3 import Client
+
+logger = logging.getLogger(__name__)
+
+
+class _S3SeekableIO(IO[bytes]):
+    """
+    _S3SeekableIO wraps boto3.StreamingBody to allow for seeking. Seeking is achieved by closing the
+    existing connection and re-opening a new one, passing the correct HTTP Range header.
+
+    Parameters
+    ----------
+    bucket: str
+        The S3 bucket
+    key: str
+        The S3 key
+    version_id: str, optional
+        A version ID of the object, when the S3 bucket is versioned
+    boto3_client: boto3 S3 Client, optional
+        An optional boto3 S3 client. If missing, a new one will be created.
+    sdk_options: dict, optional
+        Dictionary of options that will be passed to the S3 Client get_object API call
+    """
+
+    def __init__(
+        self, bucket: str, key: str, version_id: Optional[str] = None, boto3_client=Optional["Client"], **sdk_options
+    ):
+        self.bucket = bucket
+        self.key = key
+
+        # Holds the current position in the stream
+        self._position = 0
+
+        # Stores the closed state of the stream
+        self._closed: bool = False
+
+        # Caches the size of the object
+        self._size: Optional[int] = None
+
+        self._s3_client: Optional["Client"] = boto3_client
+        self._raw_stream: Optional[PowertoolsStreamingBody] = None
+
+        self._sdk_options = sdk_options
+        self._sdk_options["Bucket"] = bucket
+        self._sdk_options["Key"] = key
+        if version_id is not None:
+            self._sdk_options["VersionId"] = version_id
+
+    @property
+    def s3_client(self) -> "Client":
+        """
+        Returns a boto3 S3 client
+        """
+        if self._s3_client is None:
+            self._s3_client = boto3.client("s3")
+        return self._s3_client
+
+    @property
+    def size(self) -> int:
+        """
+        Retrieves the size of the S3 object
+        """
+        if self._size is None:
+            logger.debug("Getting size of S3 object")
+            self._size = self.s3_client.head_object(**self._sdk_options).get("ContentLength", 0)
+        return self._size
+
+    @property
+    def raw_stream(self) -> PowertoolsStreamingBody:
+        """
+        Returns the boto3 StreamingBody, starting the stream from the seeked position.
+        """
+        if self._raw_stream is None:
+            range_header = f"bytes={self._position}-"
+            logger.debug(f"Starting new stream at {range_header}")
+            self._raw_stream = self.s3_client.get_object(Range=range_header, **self._sdk_options).get("Body")
+            self._closed = False
+
+        return self._raw_stream
+
+    def seek(self, offset: int, whence: int = io.SEEK_SET) -> int:
+        """
+        Seeks the current object, invalidating the underlying stream if the position changes.
+        """
+        current_position = self._position
+
+        if whence == io.SEEK_SET:
+            self._position = offset
+        elif whence == io.SEEK_CUR:
+            self._position += offset
+        elif whence == io.SEEK_END:
+            self._position = self.size + offset
+        else:
+            raise ValueError(f"invalid whence ({whence}, should be {io.SEEK_SET}, {io.SEEK_CUR}, {io.SEEK_END})")
+
+        # Invalidate the existing stream, so a new one will be open on the next IO operation.
+        #
+        # Some consumers of this class might call seek multiple times, without affecting the net position.
+        # zipfile.ZipFile does this often. If we just blindly invalidated the stream, we would have to re-open
+        # an S3 HTTP connection just to continue reading on the same position as before, which would be inefficient.
+        #
+        # So we only invalidate it if there's a net position change after seeking, and we have an existing S3 connection
+        if current_position != self._position and self._raw_stream is not None:
+            self._raw_stream.close()
+            self._raw_stream = None
+
+        return self._position
+
+    def seekable(self) -> bool:
+        return True
+
+    def readable(self) -> bool:
+        return True
+
+    def writable(self) -> bool:
+        return False
+
+    def tell(self) -> int:
+        return self._position
+
+    def read(self, size: Optional[int] = -1) -> bytes:
+        size = None if size == -1 else size
+        data = self.raw_stream.read(size)
+        if data is not None:
+            self._position += len(data)
+        return data
+
+    def readline(self, size: Optional[int] = None) -> bytes:
+        data = self.raw_stream.readline(size)
+        self._position += len(data)
+        return data
+
+    def readlines(self, hint: int = -1) -> List[bytes]:
+        # boto3's StreamingResponse doesn't implement the "hint" parameter
+        data = self.raw_stream.readlines()
+        self._position += sum(len(line) for line in data)
+        return data
+
+    @property
+    def closed(self) -> bool:
+        return self._closed
+
+    def __next__(self):
+        return self.raw_stream.__next__()
+
+    def __iter__(self):
+        return self.raw_stream.__iter__()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *kwargs):
+        self.close()
+
+    def close(self) -> None:
+        self.raw_stream.close()
+        self._closed = True
+
+    def fileno(self) -> int:
+        raise NotImplementedError("this stream is not backed by a file descriptor")
+
+    def flush(self) -> None:
+        raise NotImplementedError("this stream is not writable")
+
+    def isatty(self) -> bool:
+        return False
+
+    def truncate(self, size: Optional[int] = 0) -> int:
+        raise NotImplementedError("this stream is not writable")
+
+    def write(self, data: AnyStr) -> int:
+        raise NotImplementedError("this stream is not writable")
+
+    def writelines(self, lines: Iterable[AnyStr]) -> None:
+        raise NotImplementedError("this stream is not writable")