[PR #10529/492f63dc backport][3.12] Fixed bug that lead to infinite wait for dns futures (#10560)

**This is a backport of PR #10529 as merged into master
(492f63d).**

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## What do these changes do?

Fixed bug that lead to infinite wait for dns futures when exception
occured in trace.send_dns_cache_miss call.

## Are there changes in behavior for the user?

No

## Is it a substantial burden for the maintainers to support this?

No

## Related issue number

No issue. 

## Checklist

- [x] I think the code is well written
- [x] Unit tests for the changes exist
- [x] Documentation reflects the changes
- [x] If you provide code modification, please add yourself to
`CONTRIBUTORS.txt`
  * The format is &lt;Name&gt; &lt;Surname&gt;.
  * Please keep alphabetical order, the file is sorted by names.
- [x] Add a new news fragment into the `CHANGES/` folder
  * name it `<issue_or_pr_num>.<type>.rst` (e.g. `588.bugfix.rst`)
  * if you don't have an issue number, change it to the pull request
    number after creating the PR
    * `.bugfix`: A bug fix for something the maintainers deemed an
      improper undesired behavior that got corrected to match
      pre-agreed expectations.
    * `.feature`: A new behavior, public APIs. That sort of stuff.
    * `.deprecation`: A declaration of future API removals and breaking
      changes in behavior.
    * `.breaking`: When something public is removed in a breaking way.
      Could be deprecated in an earlier release.
    * `.doc`: Notable updates to the documentation structure or build
      process.
    * `.packaging`: Notes for downstreams about unobvious side effects
      and tooling. Changes in the test invocation considerations and
      runtime assumptions.
    * `.contrib`: Stuff that affects the contributor experience. e.g.
      Running tests, building the docs, setting up the development
      environment.
    * `.misc`: Changes that are hard to assign to any of the above
      categories.
  * Make sure to use full sentences with correct case and punctuation,
    for example:
    ```rst
    Fixed issue with non-ascii contents in doctest text files
    -- by :user:`contributor-gh-handle`.
    ```

Co-authored-by: Alexey Stavrov <[email protected]>

Author: patchback[bot]

CHANGES/10529.bugfix.rst

@@ -0,0 +1,2 @@
+Fixed an issue where dns queries were delayed indefinitely when an exception occurred in a ``trace.send_dns_cache_miss``
+-- by :user:`logioniz`.

CONTRIBUTORS.txt

@@ -31,6 +31,7 @@ Alexandru Mihai
 Alexey Firsov
 Alexey Nikitin
 Alexey Popravka
+Alexey Stavrov
 Alexey Stepanov
 Amin Etesamian
 Amit Tulshyan

aiohttp/connector.py

@@ -1025,11 +1025,11 @@ async def _resolve_host_with_throttle(
         This method must be run in a task and shielded from cancellation
         to avoid cancelling the underlying lookup.
         """
-        if traces:
-            for trace in traces:
-                await trace.send_dns_cache_miss(host)
         try:
             if traces:
+                for trace in traces:
+                    await trace.send_dns_cache_miss(host)
+
                 for trace in traces:
                     await trace.send_dns_resolvehost_start(host)
 

tests/test_connector.py

@@ -3497,6 +3497,61 @@ async def send_dns_cache_hit(self, *args: object, **kwargs: object) -> None:
     await connector.close()
 
 
+async def test_connector_resolve_in_case_of_trace_cache_miss_exception(
+    loop: asyncio.AbstractEventLoop,
+) -> None:
+    token: ResolveResult = {
+        "hostname": "localhost",
+        "host": "127.0.0.1",
+        "port": 80,
+        "family": socket.AF_INET,
+        "proto": 0,
+        "flags": socket.AI_NUMERICHOST,
+    }
+
+    request_count = 0
+
+    class DummyTracer(Trace):
+        def __init__(self) -> None:
+            """Dummy"""
+
+        async def send_dns_cache_hit(self, *args: object, **kwargs: object) -> None:
+            """Dummy send_dns_cache_hit"""
+
+        async def send_dns_resolvehost_start(
+            self, *args: object, **kwargs: object
+        ) -> None:
+            """Dummy send_dns_resolvehost_start"""
+
+        async def send_dns_resolvehost_end(
+            self, *args: object, **kwargs: object
+        ) -> None:
+            """Dummy send_dns_resolvehost_end"""
+
+        async def send_dns_cache_miss(self, *args: object, **kwargs: object) -> None:
+            nonlocal request_count
+            request_count += 1
+            if request_count <= 1:
+                raise Exception("first attempt")
+
+    async def resolve_response() -> List[ResolveResult]:
+        await asyncio.sleep(0)
+        return [token]
+
+    with mock.patch("aiohttp.connector.DefaultResolver") as m_resolver:
+        m_resolver().resolve.return_value = resolve_response()
+
+        connector = TCPConnector()
+        traces = [DummyTracer()]
+
+        with pytest.raises(Exception):
+            await connector._resolve_host("", 0, traces)
+
+        await connector._resolve_host("", 0, traces) == [token]
+
+    await connector.close()
+
+
 async def test_connector_does_not_remove_needed_waiters(
     loop: asyncio.AbstractEventLoop, key: ConnectionKey
 ) -> None: