Cruft PRs: wait for fork creation (#202)

scripts/pyproject.toml

@@ -65,7 +65,7 @@ line-length = 120
 [tool.ruff]
 target-version = "py311"
 line-length = 120
-allowed-confusables = ["’"]
+allowed-confusables = ["’", "×"]
 select = [
     "A",
     "ARG",
@@ -96,6 +96,7 @@ select = [
 ignore = [
     "S101",  # assert should be allowed
     "S603",  # subprocess with shell=False should be allowed
+    "S311",  # we don’t need cryptographically secure RNG
 ]
 unfixable = ["RUF001"]  # never “fix” “confusables”
 

scripts/src/scverse_template_scripts/backoff.py

@@ -0,0 +1,23 @@
+import random
+import time
+from collections.abc import Callable
+from typing import TypeVar
+
+T = TypeVar("T")
+
+
+def retry_with_backoff(
+    fn: Callable[[], T],
+    retries: int = 5,
+    backoff_in_seconds: int | float = 1,
+    exc_cls: type = Exception,
+) -> T:
+    exc = None
+    for x in range(retries):
+        try:
+            return fn()
+        except exc_cls as _exc:
+            exc = _exc
+            sleep = backoff_in_seconds * 2**x + random.uniform(0, 1)
+            time.sleep(sleep)
+    raise exc

scripts/src/scverse_template_scripts/cruft_prs.py

@@ -3,6 +3,7 @@
 Uses `template-repos.yml` from `scverse/ecosystem-packages`.
 """
 
+import math
 import os
 import sys
 from collections.abc import Generator
@@ -17,13 +18,15 @@
 from furl import furl
 from git.repo import Repo
 from git.util import Actor
-from github import ContentFile, Github
+from github import ContentFile, Github, UnknownObjectException
 from github.GitRelease import GitRelease as GHRelease
 from github.NamedUser import NamedUser
 from github.PullRequest import PullRequest
 from github.Repository import Repository as GHRepo
 from yaml import safe_load
 
+from .backoff import retry_with_backoff
+
 log = getLogger(__name__)
 
 PR_BODY_TEMPLATE = """\
@@ -163,10 +166,17 @@ def cruft_update(con: GitHubConnection, repo: GHRepo, path: Path, pr: PR) -> boo
     return True
 
 
+# GitHub says that up to 5 minutes of wait are OK,
+# So we error our once we wait longer, i.e. when 2ⁿ = 5 min × 60 sec/min
+n_retries = math.ceil(math.log(5 * 60) / math.log(2))  # = ⌈~8.22⌉ = 9
+# Due to exponential backoff, we’ll maximally wait 2⁹ sec, or 8.5 min
+
+
 def get_fork(con: GitHubConnection, repo: GHRepo) -> GHRepo:
     if fork := next((f for f in repo.get_forks() if f.owner.id == con.user.id), None):
         return fork
-    return repo.create_fork()
+    fork = repo.create_fork()
+    return retry_with_backoff(lambda: con.gh.get_repo(fork.id), retries=n_retries, exc_cls=UnknownObjectException)
 
 
 def make_pr(con: GitHubConnection, release: GHRelease, repo_url: str) -> None: