Add Hygraph circuit breaker and caching with fallback metrics #124
There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| """Simple cache helper that prefers Redis but falls back to an in-memory store.""" | ||
|
|
||
| from __future__ import annotations | ||
|
|
||
| import json | ||
| import os | ||
| import threading | ||
| import time | ||
| from typing import Any, Dict, Optional | ||
|
|
||
| try: # pragma: no cover - optional dependency | ||
| import redis # type: ignore | ||
| except Exception: # pragma: no cover - optional dependency | ||
| redis = None # type: ignore[assignment] | ||
|
|
||
|
|
||
| class RedisCache: | ||
| """Tiny wrapper that abstracts Redis availability.""" | ||
|
|
||
| def __init__(self, url: str | None = None, *, namespace: str = "hygraph") -> None: | ||
| self._url = url or os.getenv("HYGRAPH_CACHE_URL") or os.getenv("REDIS_URL") | ||
| self._namespace = namespace | ||
| self._lock = threading.Lock() | ||
| self._memory: Dict[str, tuple[str, Optional[float]]] = {} | ||
| if redis is not None and self._url: | ||
| self._client = redis.Redis.from_url(self._url, decode_responses=True) | ||
| else: # pragma: no cover - exercised implicitly when redis missing | ||
| self._client = None | ||
|
|
||
| def _ns(self, key: str) -> str: | ||
| return f"{self._namespace}:{key}" | ||
|
|
||
| def get(self, key: str) -> Any | None: | ||
| namespaced = self._ns(key) | ||
| if self._client is not None: | ||
| raw = self._client.get(namespaced) | ||
| return json.loads(raw) if raw else None | ||
| with self._lock: | ||
| value = self._memory.get(namespaced) | ||
| if value is None: | ||
| return None | ||
| raw, expires_at = value | ||
| if expires_at is not None and expires_at < time.time(): | ||
| del self._memory[namespaced] | ||
| return None | ||
| return json.loads(raw) | ||
|
|
||
| def set(self, key: str, value: Any, *, ttl: int | None = None) -> None: | ||
| payload = json.dumps(value) | ||
| namespaced = self._ns(key) | ||
| if self._client is not None: | ||
| if ttl is not None: | ||
| self._client.setex(namespaced, ttl, payload) | ||
| else: | ||
| self._client.set(namespaced, payload) | ||
| return | ||
| expires_at = (time.time() + ttl) if ttl else None | ||
| with self._lock: | ||
| self._memory[namespaced] = (payload, expires_at) | ||
|
|
||
| def clear(self, key: str) -> None: | ||
| namespaced = self._ns(key) | ||
| if self._client is not None: | ||
| self._client.delete(namespaced) | ||
| return | ||
|
||
| with self._lock: | ||
| self._memory.pop(namespaced, None) | ||
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,84 @@ | ||
| """Circuit breaker utility for wrapping outbound service calls.""" | ||
|
|
||
| from __future__ import annotations | ||
|
|
||
| import time | ||
| from dataclasses import dataclass, field | ||
| from typing import Any, Callable, TypeVar | ||
|
|
||
|
|
||
| T = TypeVar("T") | ||
|
|
||
|
|
||
| class CircuitOpenError(RuntimeError): | ||
| """Raised when the circuit breaker refuses to execute a call.""" | ||
|
|
||
| def __init__(self, message: str = "Circuit breaker is open", *, fallback: Any | None = None) -> None: | ||
| super().__init__(message) | ||
| self.fallback = fallback | ||
|
|
||
|
|
||
| @dataclass | ||
| class CircuitBreaker: | ||
| """Simple circuit breaker implementation with configurable thresholds.""" | ||
|
|
||
| failure_threshold: int = 5 | ||
| recovery_timeout: float = 30.0 | ||
| success_threshold: int = 1 | ||
| state: str = field(default="CLOSED", init=False) | ||
| failure_count: int = field(default=0, init=False) | ||
| success_count: int = field(default=0, init=False) | ||
| last_failure_time: float | None = field(default=None, init=False) | ||
|
|
||
| CLOSED: str = field(default="CLOSED", init=False) | ||
| OPEN: str = field(default="OPEN", init=False) | ||
| HALF_OPEN: str = field(default="HALF_OPEN", init=False) | ||
|
|
||
| def call(self, func: Callable[..., T], *args: Any, **kwargs: Any) -> T: | ||
| """Execute ``func`` respecting the breaker state machine.""" | ||
|
|
||
| now = time.monotonic() | ||
| if self.state == self.OPEN: | ||
| if self.last_failure_time is None or (now - self.last_failure_time) < self.recovery_timeout: | ||
| raise CircuitOpenError() | ||
| self.state = self.HALF_OPEN | ||
| self.success_count = 0 | ||
|
|
||
| try: | ||
| result = func(*args, **kwargs) | ||
| except Exception: # noqa: BLE001 | ||
| self._record_failure() | ||
| raise | ||
|
|
||
| self._record_success() | ||
| return result | ||
|
|
||
| def _record_failure(self) -> None: | ||
| now = time.monotonic() | ||
| if self.state == self.HALF_OPEN: | ||
| self._trip(now) | ||
| return | ||
|
|
||
| self.failure_count += 1 | ||
| if self.failure_count >= self.failure_threshold: | ||
| self._trip(now) | ||
|
|
||
| def _record_success(self) -> None: | ||
| if self.state == self.HALF_OPEN: | ||
| self.success_count += 1 | ||
| if self.success_count >= self.success_threshold: | ||
| self._reset() | ||
| else: | ||
| self._reset() | ||
|
|
||
| def _trip(self, when: float) -> None: | ||
| self.state = self.OPEN | ||
| self.last_failure_time = when | ||
| self.failure_count = 0 | ||
| self.success_count = 0 | ||
|
|
||
| def _reset(self) -> None: | ||
| self.state = self.CLOSED | ||
| self.failure_count = 0 | ||
| self.success_count = 0 | ||
| self.last_failure_time = None |
Oops, something went wrong.
Oops, something went wrong.
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
Address the pipeline failure by refining the type-ignore comment.
The pipeline failure at line 12 indicates that the broad
# type: ignorecomment may be unnecessary or should be more specific. Consider using a more precise suppression like# type: ignore[import-not-found]or remove it if the import can be typed correctly withTYPE_CHECKINGguards.Note: Also consider catching only
ImportErrorrather than the broadExceptionfor clarity.📝 Committable suggestion
🧰 Tools
🪛 GitHub Actions: CI
[error] 12-12: Typos/lint issues detected by ruff/typos; possibly unused type-ignore comments or redefinition.
🤖 Prompt for AI Agents