Re-use HTTP connections when remote S3 signing

The existing S3 remote signing hook function (`s3v4_rest_signer`) uses
`requests.post` to submit `POST` requests to the REST signing endpoint,
but this internally creates a new `requests.Session` for every request,
preventing any reuse of connections.

In my profiling I saw this add overhead from repeated loading of CA certs
and reestablishing of TLS connections.

This change makes the signing function a callable object that wraps a
`request.Session`, using this for `POST`ing, therefore achieving
connection reuse.

Signer callables are stored on the hook internals of the `aiobotocore`
client inside the `s3fs.S3FileSystem` instance, so use and lifetime will
match that of those instances.

The `s3fs.S3FileSystem` instances are guaranteed thread-local since:
apache#2495.

Author: lwfitzgerald

pyiceberg/io/fsspec.py

@@ -16,18 +16,20 @@
 # under the License.
 """FileIO implementation for reading and writing table files that uses fsspec compatible filesystems."""
 
+import abc
 import errno
 import json
 import logging
 import os
 import threading
 from copy import copy
-from functools import lru_cache, partial
+from functools import lru_cache
 from typing import (
     TYPE_CHECKING,
     Any,
     Callable,
     Dict,
+    Type,
     Union,
 )
 from urllib.parse import urlparse
@@ -95,38 +97,59 @@
     from botocore.awsrequest import AWSRequest
 
 
-def s3v4_rest_signer(properties: Properties, request: "AWSRequest", **_: Any) -> "AWSRequest":
-    signer_url = properties.get(S3_SIGNER_URI, properties[URI]).rstrip("/")  # type: ignore
-    signer_endpoint = properties.get(S3_SIGNER_ENDPOINT, S3_SIGNER_ENDPOINT_DEFAULT)
+class S3RequestSigner(abc.ABC):
+    """Abstract base class for S3 request signers."""
 
-    signer_headers = {}
-    if token := properties.get(TOKEN):
-        signer_headers = {"Authorization": f"Bearer {token}"}
-    signer_headers.update(get_header_properties(properties))
+    properties: Properties
 
-    signer_body = {
-        "method": request.method,
-        "region": request.context["client_region"],
-        "uri": request.url,
-        "headers": {key: [val] for key, val in request.headers.items()},
-    }
+    def __init__(self, properties: Properties) -> None:
+        self.properties = properties
+
+    @abc.abstractmethod
+    def __call__(self, request: "AWSRequest", **_: Any) -> None:
+        pass
+
+
+class S3V4RestSigner(S3RequestSigner):
+    """An S3 request signer that uses an external REST signing service to sign requests."""
+
+    session: requests.Session
 
-    response = requests.post(f"{signer_url}/{signer_endpoint.strip()}", headers=signer_headers, json=signer_body)
-    try:
-        response.raise_for_status()
-        response_json = response.json()
-    except HTTPError as e:
-        raise SignError(f"Failed to sign request {response.status_code}: {signer_body}") from e
+    def __init__(self, properties: Properties) -> None:
+        super().__init__(properties)
+        self.session = requests.Session()
 
-    for key, value in response_json["headers"].items():
-        request.headers.add_header(key, ", ".join(value))
+    def __call__(self, request: "AWSRequest", **_: Any) -> None:
+        signer_url = self.properties.get(S3_SIGNER_URI, self.properties[URI]).rstrip("/")  # type: ignore
+        signer_endpoint = self.properties.get(S3_SIGNER_ENDPOINT, S3_SIGNER_ENDPOINT_DEFAULT)
+
+        signer_headers = {}
+        if token := self.properties.get(TOKEN):
+            signer_headers = {"Authorization": f"Bearer {token}"}
+        signer_headers.update(get_header_properties(self.properties))
+
+        signer_body = {
+            "method": request.method,
+            "region": request.context["client_region"],
+            "uri": request.url,
+            "headers": {key: [val] for key, val in request.headers.items()},
+        }
+
+        response = self.session.post(f"{signer_url}/{signer_endpoint.strip()}", headers=signer_headers,
+                                     json=signer_body)
+        try:
+            response.raise_for_status()
+            response_json = response.json()
+        except HTTPError as e:
+            raise SignError(f"Failed to sign request {response.status_code}: {signer_body}") from e
 
-    request.url = response_json["uri"]
+        for key, value in response_json["headers"].items():
+            request.headers.add_header(key, ", ".join(value))
 
-    return request
+        request.url = response_json["uri"]
 
 
-SIGNERS: Dict[str, Callable[[Properties, "AWSRequest"], "AWSRequest"]] = {"S3V4RestSigner": s3v4_rest_signer}
+SIGNERS: Dict[str, Type[S3RequestSigner]] = {"S3V4RestSigner": S3V4RestSigner}
 
 
 def _file(_: Properties) -> LocalFileSystem:
@@ -144,13 +167,13 @@ def _s3(properties: Properties) -> AbstractFileSystem:
         "region_name": get_first_property_value(properties, S3_REGION, AWS_REGION),
     }
     config_kwargs = {}
-    register_events: Dict[str, Callable[[Properties], None]] = {}
+    register_events: Dict[str, Callable[[AWSRequest], None]] = {}
 
     if signer := properties.get(S3_SIGNER):
         logger.info("Loading signer %s", signer)
-        if signer_func := SIGNERS.get(signer):
-            signer_func_with_properties = partial(signer_func, properties)
-            register_events["before-sign.s3"] = signer_func_with_properties
+        if signer_cls := SIGNERS.get(signer):
+            signer = signer_cls(properties)
+            register_events["before-sign.s3"] = signer
 
             # Disable the AWS Signer
             from botocore import UNSIGNED

tests/io/test_fsspec.py

@@ -31,7 +31,7 @@
 
 from pyiceberg.exceptions import SignError
 from pyiceberg.io import fsspec
-from pyiceberg.io.fsspec import FsspecFileIO, s3v4_rest_signer
+from pyiceberg.io.fsspec import FsspecFileIO, S3V4RestSigner
 from pyiceberg.io.pyarrow import PyArrowFileIO
 from pyiceberg.typedef import Properties
 from tests.conftest import UNIFIED_AWS_SESSION_PROPERTIES
@@ -814,10 +814,11 @@ def test_s3v4_rest_signer(requests_mock: Mocker) -> None:
         "retries": {"attempt": 1, "invocation-id": "75d143fb-0219-439b-872c-18213d1c8d54"},
     }
 
-    signed_request = s3v4_rest_signer({"token": "abc", "uri": TEST_URI, "header.X-Custom-Header": "value"}, request)
+    signer = S3V4RestSigner(properties={"token": "abc", "uri": TEST_URI, "header.X-Custom-Header": "value"})
+    signer(request)
 
-    assert signed_request.url == new_uri
-    assert dict(signed_request.headers) == {
+    assert request.url == new_uri
+    assert dict(request.headers) == {
         "Authorization": "AWS4-HMAC-SHA256 Credential=ASIAQPRZZYGHUT57DL3I/20221017/us-west-2/s3/aws4_request, SignedHeaders=host;x-amz-content-sha256;x-amz-date;x-amz-security-token, Signature=430582a17d61ab02c272896fa59195f277af4bdf2121c441685e589f044bbe02",
         "Host": "bucket.s3.us-west-2.amazonaws.com",
         "User-Agent": "Botocore/1.27.59 Python/3.10.7 Darwin/21.5.0",
@@ -868,10 +869,11 @@ def test_s3v4_rest_signer_endpoint(requests_mock: Mocker) -> None:
         "retries": {"attempt": 1, "invocation-id": "75d143fb-0219-439b-872c-18213d1c8d54"},
     }
 
-    signed_request = s3v4_rest_signer({"token": "abc", "uri": TEST_URI, "s3.signer.endpoint": endpoint}, request)
+    signer = S3V4RestSigner(properties={"token": "abc", "uri": TEST_URI, "s3.signer.endpoint": endpoint})
+    signer(request)
 
-    assert signed_request.url == new_uri
-    assert dict(signed_request.headers) == {
+    assert request.url == new_uri
+    assert dict(request.headers) == {
         "Authorization": "AWS4-HMAC-SHA256 Credential=ASIAQPRZZYGHUT57DL3I/20221017/us-west-2/s3/aws4_request, SignedHeaders=host;x-amz-content-sha256;x-amz-date;x-amz-security-token, Signature=430582a17d61ab02c272896fa59195f277af4bdf2121c441685e589f044bbe02",
         "Host": "bucket.s3.us-west-2.amazonaws.com",
         "User-Agent": "Botocore/1.27.59 Python/3.10.7 Darwin/21.5.0",
@@ -909,8 +911,9 @@ def test_s3v4_rest_signer_forbidden(requests_mock: Mocker) -> None:
         "retries": {"attempt": 1, "invocation-id": "75d143fb-0219-439b-872c-18213d1c8d54"},
     }
 
+    signer = S3V4RestSigner(properties={"token": "abc", "uri": TEST_URI})
     with pytest.raises(SignError) as exc_info:
-        _ = s3v4_rest_signer({"token": "abc", "uri": TEST_URI}, request)
+        signer(request)
 
     assert (
         """Failed to sign request 401: {'method': 'HEAD', 'region': 'us-west-2', 'uri': 'https://bucket/metadata/snap-8048355899640248710-1-a5c8ea2d-aa1f-48e8-89f4-1fa69db8c742.avro', 'headers': {'User-Agent': ['Botocore/1.27.59 Python/3.10.7 Darwin/21.5.0']}}"""