fix(bot): http client perf issue (#852)

Work around for a perf issue with how httpx handles SSL.

Instead of using `httpx.AsyncClient` directly, we subclass and reuse the ssl context.

rel: encode/httpx#838

bot/kodiak/cli.py

@@ -4,10 +4,10 @@
 
 import click
 import requests
-from httpx import AsyncClient
 
 from kodiak import app_config as conf
 from kodiak.config import V1
+from kodiak.http import HttpClient
 from kodiak.queries import generate_jwt, get_token_for_install
 
 
@@ -66,7 +66,7 @@ def token_for_install(install_id: str) -> None:
     """
 
     async def get_token() -> str:
-        async with AsyncClient() as http:
+        async with HttpClient() as http:
             return await get_token_for_install(session=http, installation_id=install_id)
 
     token = asyncio.run(get_token())

bot/kodiak/http.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+import ssl
+
+from httpx import (  # noqa: I251
+    AsyncClient,
+    HTTPError,
+    HTTPStatusError,
+    Request,
+    Response,
+)
+from httpx._config import DEFAULT_TIMEOUT_CONFIG  # noqa: I251
+from httpx._types import TimeoutTypes  # noqa: I251
+
+__all__ = ["Response", "Request", "HTTPError", "HttpClient", "HTTPStatusError"]
+
+# NOTE: this has a cost to create so we may want to set this lazily on the first HttpClient creation
+context = ssl.create_default_context()
+
+
+class HttpClient(AsyncClient):
+    """
+    HTTP Client with the SSL config cached at the module level to avoid perf issues.
+    see: https://github.com/encode/httpx/issues/838
+    """
+
+    def __init__(
+        self,
+        *,
+        timeout: TimeoutTypes = DEFAULT_TIMEOUT_CONFIG,
+    ):
+
+        super().__init__(
+            verify=context,
+            timeout=timeout,
+        )

bot/kodiak/pull_request.py

@@ -5,7 +5,6 @@
 from typing import Awaitable, Callable, List, Optional, Type
 
 import structlog
-from httpx import HTTPStatusError as HTTPError
 from typing_extensions import Protocol
 
 import kodiak.app_config as conf
@@ -16,6 +15,7 @@
     RetryForSkippableChecks,
 )
 from kodiak.evaluation import mergeable
+from kodiak.http import HTTPStatusError as HTTPError
 from kodiak.queries import Client, EventInfoResponse
 
 logger = structlog.get_logger()

bot/kodiak/queries/__init__.py

@@ -6,7 +6,6 @@
 from enum import Enum
 from typing import Any, Dict, List, Mapping, MutableMapping, Optional, Union, cast
 
-import httpx as http
 import jwt
 import pydantic
 import structlog
@@ -16,7 +15,9 @@
 from typing_extensions import Literal, Protocol
 
 import kodiak.app_config as conf
+from kodiak import http
 from kodiak.config import V1, MergeMethod
+from kodiak.http import HttpClient
 from kodiak.queries.commits import Commit, CommitConnection, GitActor
 from kodiak.queries.commits import User as PullRequestCommitUser
 from kodiak.queries.commits import get_commits
@@ -825,7 +826,7 @@ def __init__(self, *, owner: str, repo: str, installation_id: str):
         self.installation_id = installation_id
         # NOTE: We must call `await session.close()` when we are finished with our session.
         # We implement an async context manager this handle this.
-        self.session = http.AsyncClient(
+        self.session = HttpClient(
             # infinite timeout to match behavior of old, requests_async http
             # client. As a backup we have an asyncio timeout of 30 seconds.
             timeout=None

bot/kodiak/refresh_pull_requests.py

@@ -21,12 +21,12 @@
 import structlog
 from asyncio_redis.connection import Connection as RedisConnection
 from asyncio_redis.replies import BlockingPopReply
-from httpx import AsyncClient
 from pydantic import BaseModel
 from sentry_sdk.integrations.logging import LoggingIntegration
 
 from kodiak import app_config as conf
 from kodiak import redis_client
+from kodiak.http import HttpClient
 from kodiak.logging import SentryProcessor, add_request_info_processor
 from kodiak.queries import generate_jwt, get_token_for_install
 from kodiak.queue import WebhookEvent
@@ -106,7 +106,7 @@
 """
 
 
-async def get_login_for_install(*, http: AsyncClient, installation_id: str) -> str:
+async def get_login_for_install(*, http: HttpClient, installation_id: str) -> str:
     app_token = generate_jwt(
         private_key=conf.PRIVATE_KEY, app_identifier=conf.GITHUB_APP_ID
     )
@@ -124,7 +124,7 @@ async def get_login_for_install(*, http: AsyncClient, installation_id: str) -> s
 async def refresh_pull_requests_for_installation(
     *, installation_id: str, redis: RedisConnection
 ) -> None:
-    async with AsyncClient() as http:
+    async with HttpClient() as http:
         login = await get_login_for_install(http=http, installation_id=installation_id)
         token = await get_token_for_install(
             session=http, installation_id=installation_id

bot/kodiak/test_pull_request.py

@@ -2,13 +2,13 @@
 
 from typing import Any, Awaitable, Callable, Dict, List, Mapping, Optional, Type, cast
 
-import httpx as requests
 import pytest
-from httpx import Request
 from typing_extensions import Protocol
 
+import kodiak.http as requests
 from kodiak.config import V1, Merge, MergeMethod
 from kodiak.errors import ApiCallException
+from kodiak.http import Request
 from kodiak.pull_request import PRV2, EventInfoResponse, QueueForMergeCallback
 from kodiak.queries import (
     BranchProtectionRule,

bot/kodiak/test_queries.py

@@ -8,11 +8,11 @@
 
 import asyncio_redis
 import pytest
-from httpx import Request, Response
 from pytest_mock import MockFixture
 
 from kodiak import app_config as conf
 from kodiak.config import V1, Merge, MergeMethod
+from kodiak.http import Request, Response
 from kodiak.queries import (
     BranchProtectionRule,
     CheckConclusionState,

bot/pyproject.toml

@@ -47,6 +47,7 @@ pytest-cov = "^2.10"
 flake8-pyi = "^20.10"
 types-requests = "^2.28.0"
 types-toml = "^0.10.7"
+flake8-tidy-imports = "^4.8.0"
 
 [tool.poetry.plugins."pytest11"]
 "pytest_plugin" = "pytest_plugin.plugin"

bot/tox.ini

@@ -9,6 +9,9 @@ filterwarnings =
   ignore::pytest.PytestDeprecationWarning
   ignore::DeprecationWarning:asyncio_redis
 [flake8]
+banned-modules =
+  httpx.* = Use kodiak.http
+ban-relative-imports = true
 ignore =
     ; formatting handled by black
     ; https://pycodestyle.readthedocs.io/en/latest/intro.html#error-codes