Retry setup-python on a transient download failure

.github/workflows/ci.yml

@@ -1499,9 +1499,24 @@ jobs:
         with:
           node-version: '24.21.0' # exact: bump deliberately (#1645)
 
-      - name: Setup Python
+      - name: Setup Python (attempt 1)
+        # setup-python downloads 3.12.10 on runners that don't cache it,
+        # which takes ~6 s. On 2026-10-28 (run 40771482790) the manifest
+        # fetch died on `getaddrinfo EAI_AGAIN raw.githubusercontent.com`
+        # and the step held the leg for 19 min before failing it. Cap the
+        # download and try once more; a second failure is not a blip.
+        id: setup-python
         if: matrix.suite == 'e2e_pypi' || matrix.uv != '' || matrix.poetry != '' || matrix.pdm != '' || matrix.hatch != ''
         uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
+        timeout-minutes: 4
+        continue-on-error: true
+        with:
+          python-version: '3.12.10' # exact: last 3.12 with Windows+macOS builds; bump deliberately (#1645)
+
+      - name: Setup Python (attempt 2)
+        if: (matrix.suite == 'e2e_pypi' || matrix.uv != '' || matrix.poetry != '' || matrix.pdm != '' || matrix.hatch != '') && steps.setup-python.outcome != 'success'
+        uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
+        timeout-minutes: 4
         with:
           python-version: '3.12.10' # exact: last 3.12 with Windows+macOS builds; bump deliberately (#1645)
 
@@ -2790,9 +2805,20 @@ jobs:
           bun --version
           node --no-warnings "$js" --version
 
-      - name: Setup Python + uv
+      - name: Setup Python (attempt 1)
+        # Capped and retried once, as in the e2e job.
+        id: setup-python
         if: steps.gate.outputs.run == 'true'
         uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
+        timeout-minutes: 4
+        continue-on-error: true
+        with:
+          python-version: '3.12.10' # exact: last 3.12 with Windows+macOS builds; bump deliberately (#1645)
+
+      - name: Setup Python (attempt 2)
+        if: (steps.gate.outputs.run == 'true') && steps.setup-python.outcome != 'success'
+        uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
+        timeout-minutes: 4
         with:
           python-version: '3.12.10' # exact: last 3.12 with Windows+macOS builds; bump deliberately (#1645)
 

scripts/tests/test_merge_queue_fail_fast.py

@@ -116,16 +116,29 @@ def test_no_job_tolerates_failure(self):
         # A job-level continue-on-error would let ci-ok pass despite a failed
         # job, and this script would then cancel a run that could still land.
         # A step-level one hides that step's failure the same way, so only
-        # the capped cache restores may carry it: a miss there just means
-        # building cold.
+        # the capped cache restores may carry it (a miss there just means
+        # building cold), plus a capped first attempt that the very next
+        # step retries without tolerance.
         self.assertIsNone(re.search(r"^    continue-on-error:", self.text, re.M))
         steps = re.split(r"(?m)^      - ", self.text)
-        tolerant = [s for s in steps if re.search(r"(?m)^\s*continue-on-error:", s)]
+        tolerant = [i for i, s in enumerate(steps) if re.search(r"(?m)^\s*continue-on-error:", s)]
         self.assertTrue(tolerant)
-        for step in tolerant:
-            self.assertRegex(step, r"(?m)^        uses: (Swatinem/rust-cache|actions/cache/restore)@", step[:80])
+        for i in tolerant:
+            step = steps[i]
             self.assertRegex(step, r"(?m)^        timeout-minutes: \d+$", step[:80])
             self.assertRegex(step, r"(?m)^        continue-on-error: true$", step[:80])
+            if re.search(r"(?m)^        uses: (Swatinem/rust-cache|actions/cache/restore)@", step):
+                continue
+            self.assertRegex(step, r"^name: .* \(attempt 1\)\n", step[:80])
+            sid = re.search(r"(?m)^        id: (\S+)$", step).group(1)
+            retry = steps[i + 1]
+            self.assertRegex(retry, r"^name: .* \(attempt 2\)\n", retry[:80])
+            self.assertIn(f"steps.{sid}.outcome != 'success'", retry, retry[:80])
+            self.assertEqual(
+                re.search(r"(?m)^        uses: .*$", step).group(0),
+                re.search(r"(?m)^        uses: .*$", retry).group(0),
+            )
+            self.assertNotRegex(retry, r"(?m)^\s*continue-on-error:", retry[:80])
 
     def test_every_cache_restore_is_capped(self):
         # An uncapped restore that hangs holds the queue head until the job