Add connect retries

httpx/_client.py

@@ -1,14 +1,18 @@
 import functools
+import time
 import typing
 from types import TracebackType
 
 import httpcore
 
 from ._auth import Auth, BasicAuth, FunctionAuth
 from ._config import (
+    CONNECT_RETRIES_BACKOFF_FACTOR,
+    DEFAULT_CONNECT_RETRIES,
     DEFAULT_LIMITS,
     DEFAULT_MAX_REDIRECTS,
     DEFAULT_TIMEOUT_CONFIG,
+    IDEMPOTENT_METHODS,
     UNSET,
     Limits,
     Proxy,
@@ -19,6 +23,8 @@
 from ._content_streams import ContentStream
 from ._exceptions import (
     HTTPCORE_EXC_MAP,
+    ConnectError,
+    ConnectTimeout,
     InvalidURL,
     RemoteProtocolError,
     RequestBodyUnavailable,
@@ -45,9 +51,11 @@
 from ._utils import (
     NetRCInfo,
     URLPattern,
+    exponential_backoff,
     get_environment_proxies,
     get_logger,
     same_origin,
+    sleep,
     warn_deprecated,
 )
 
@@ -66,6 +74,7 @@ def __init__(
         cookies: CookieTypes = None,
         timeout: TimeoutTypes = DEFAULT_TIMEOUT_CONFIG,
         max_redirects: int = DEFAULT_MAX_REDIRECTS,
+        connect_retries: int = DEFAULT_CONNECT_RETRIES,
         base_url: URLTypes = "",
         trust_env: bool = True,
     ):
@@ -77,6 +86,7 @@ def __init__(
         self._cookies = Cookies(cookies)
         self._timeout = Timeout(timeout)
         self.max_redirects = max_redirects
+        self.connect_retries = connect_retries
         self._trust_env = trust_env
         self._netrc = NetRCInfo()
 
@@ -484,6 +494,8 @@ class Client(BaseClient):
     * **limits** - *(optional)* The limits configuration to use.
     * **max_redirects** - *(optional)* The maximum number of redirect responses
     that should be followed.
+    * **connect_retries** - *(optional)* The maximum number of retries when trying to
+    establish a connection.
     * **base_url** - *(optional)* A URL to use as the base when building
     request URLs.
     * **transport** - *(optional)* A transport class to use for sending requests
@@ -509,6 +521,7 @@ def __init__(
         limits: Limits = DEFAULT_LIMITS,
         pool_limits: Limits = None,
         max_redirects: int = DEFAULT_MAX_REDIRECTS,
+        connect_retries: int = DEFAULT_CONNECT_RETRIES,
         base_url: URLTypes = "",
         transport: httpcore.SyncHTTPTransport = None,
         app: typing.Callable = None,
@@ -521,6 +534,7 @@ def __init__(
             cookies=cookies,
             timeout=timeout,
             max_redirects=max_redirects,
+            connect_retries=connect_retries,
             base_url=base_url,
             trust_env=trust_env,
         )
@@ -766,7 +780,7 @@ def _send_handling_auth(
         auth_flow = auth.auth_flow(request)
         request = next(auth_flow)
         while True:
-            response = self._send_single_request(request, timeout)
+            response = self._send_handling_retries(request, timeout)
             if auth.requires_response_body:
                 response.read()
             try:
@@ -782,6 +796,22 @@ def _send_handling_auth(
                 request = next_request
                 history.append(response)
 
+    def _send_handling_retries(self, request: Request, timeout: Timeout) -> Response:
+        connect_retries_left = self.connect_retries
+        delays = exponential_backoff(factor=CONNECT_RETRIES_BACKOFF_FACTOR)
+
+        while True:
+            try:
+                return self._send_single_request(request, timeout)
+            except (ConnectError, ConnectTimeout):
+                if request.method not in IDEMPOTENT_METHODS:
+                    raise
+                if connect_retries_left <= 0:
+                    raise
+                connect_retries_left -= 1
+                delay = next(delays)
+                time.sleep(delay)
+
     def _send_single_request(self, request: Request, timeout: Timeout) -> Response:
         """
         Sends a single request, without handling any redirections.
@@ -1091,6 +1121,8 @@ class AsyncClient(BaseClient):
     * **limits** - *(optional)* The limits configuration to use.
     * **max_redirects** - *(optional)* The maximum number of redirect responses
     that should be followed.
+    * **connect_retries** - *(optional)* The maximum number of retries when trying to
+    establish a connection.
     * **base_url** - *(optional)* A URL to use as the base when building
     request URLs.
     * **transport** - *(optional)* A transport class to use for sending requests
@@ -1116,6 +1148,7 @@ def __init__(
         limits: Limits = DEFAULT_LIMITS,
         pool_limits: Limits = None,
         max_redirects: int = DEFAULT_MAX_REDIRECTS,
+        connect_retries: int = DEFAULT_CONNECT_RETRIES,
         base_url: URLTypes = "",
         transport: httpcore.AsyncHTTPTransport = None,
         app: typing.Callable = None,
@@ -1128,6 +1161,7 @@ def __init__(
             cookies=cookies,
             timeout=timeout,
             max_redirects=max_redirects,
+            connect_retries=connect_retries,
             base_url=base_url,
             trust_env=trust_env,
         )
@@ -1375,7 +1409,7 @@ async def _send_handling_auth(
         auth_flow = auth.auth_flow(request)
         request = next(auth_flow)
         while True:
-            response = await self._send_single_request(request, timeout)
+            response = await self._send_handling_retries(request, timeout)
             if auth.requires_response_body:
                 await response.aread()
             try:
@@ -1391,6 +1425,24 @@ async def _send_handling_auth(
                 request = next_request
                 history.append(response)
 
+    async def _send_handling_retries(
+        self, request: Request, timeout: Timeout
+    ) -> Response:
+        connect_retries_left = self.connect_retries
+        delays = exponential_backoff(factor=CONNECT_RETRIES_BACKOFF_FACTOR)
+
+        while True:
+            try:
+                return await self._send_single_request(request, timeout)
+            except (ConnectError, ConnectTimeout):
+                if request.method not in IDEMPOTENT_METHODS:
+                    raise
+                if connect_retries_left <= 0:
+                    raise
+                connect_retries_left -= 1
+                delay = next(delays)
+                await sleep(delay)
+
     async def _send_single_request(
         self, request: Request, timeout: Timeout
     ) -> Response:

httpx/_config.py

@@ -30,6 +30,7 @@
     ]
 )
 
+IDEMPOTENT_METHODS = {"GET", "HEAD", "PUT", "DELETE", "OPTIONS", "TRACE"}
 
 logger = get_logger(__name__)
 
@@ -413,3 +414,5 @@ def __repr__(self) -> str:
 DEFAULT_TIMEOUT_CONFIG = Timeout(timeout=5.0)
 DEFAULT_LIMITS = Limits(max_connections=100, max_keepalive_connections=20)
 DEFAULT_MAX_REDIRECTS = 20
+DEFAULT_CONNECT_RETRIES = 0
+CONNECT_RETRIES_BACKOFF_FACTOR = 0.5  # 0s, 0.5s, 1s, 2s, 4s, etc.

httpx/_utils.py

@@ -1,5 +1,7 @@
+import asyncio
 import codecs
 import collections
+import itertools
 import logging
 import mimetypes
 import netrc
@@ -14,6 +16,8 @@
 from types import TracebackType
 from urllib.request import getproxies
 
+import sniffio
+
 from ._types import PrimitiveData
 
 if typing.TYPE_CHECKING:  # pragma: no cover
@@ -529,3 +533,20 @@ def __eq__(self, other: typing.Any) -> bool:
 
 def warn_deprecated(message: str) -> None:  # pragma: nocover
     warnings.warn(message, DeprecationWarning, stacklevel=2)
+
+
+async def sleep(seconds: float) -> None:
+    library = sniffio.current_async_library()
+    if library == "trio":
+        import trio
+
+        await trio.sleep(seconds)
+    else:
+        assert library == "asyncio"
+        await asyncio.sleep(seconds)
+
+
+def exponential_backoff(factor: float) -> typing.Iterator[float]:
+    yield 0
+    for n in itertools.count(2):
+        yield factor * (2 ** (n - 2))