Implement Gateway(providers, clock, sleep, max_retries, breaker_threshold, cooldown) with
complete(prompt) -> {"text", "provider", "attempts"}. providers is a list of objects with a name and
a complete(prompt) method that returns text or raises ProviderError (provided) with a status.
Policy:
cooldown
seconds ago by clock()).max_retries times, sleeping
0.5 × 2**i seconds before retry i (0, 1, …) using sleep. Then move on to the next provider.breaker_threshold, the circuit opens (stop using that provider
immediately, even mid-retries). A provider whose cooldown has passed is tried again; a success closes
its circuit, a failure re-opens it.BadRequest (provided) at once — don't try other providers.AllProvidersFailed (provided).attempts counts every provider call made for this prompt. The harness replays prompts with scripted
provider failures; each provider call takes 1 second on the fake clock.
Implement Gateway. Input: providers, clock, sleep, max_retries: int, breaker_threshold: int, cooldown: float. Returns: a class.
Prompt a: primary fails, sleep 0.5, fails again (retries exhausted), backup answers. Prompt b: primary has 2 failures (below 3) and its script is empty now, so it answers.
Two failures open primary's circuit; backup's 400 raises BadRequest for x. For y, primary is still open (skipped) and backup has one failure (below 2), so it is tried and answers.
This code runs before yours (fake clients, clocks and the test harness). You can use its names; don't edit them.
class ProviderError(Exception):
def __init__(self, status):
super().__init__(f"HTTP {status}")
self.status = status
class BadRequest(Exception):
pass
class AllProvidersFailed(Exception):
pass
class FakeProvider:
def __init__(self, name, script, now):
self.name, self.script, self.now, self.calls = name, list(script), now, 0
def complete(self, prompt):
self.calls += 1
self.now["t"] += 1.0
outcome = self.script.pop(0) if self.script else "ok"
if outcome != "ok":
raise ProviderError(outcome)
return f"{self.name}:{prompt}"
def __harness__(cls, scripts, prompts, max_retries, threshold, cooldown):
now = {"t": 0.0}
providers = [FakeProvider(name, script, now) for name, script in scripts]
def sleep(seconds):
now["t"] += seconds
gateway = cls(providers, lambda: now["t"], sleep, max_retries, threshold, cooldown)
results = []
for p in prompts:
try:
r = gateway.complete(p)
results.append([r["provider"], r["attempts"]])
except BadRequest:
results.append("bad_request")
except AllProvidersFailed:
results.append("all_failed")
return {"results": results, "calls": {p.name: p.calls for p in providers}, "clock": round(now["t"], 3)}
class Gateway:
def __init__(self, providers, clock, sleep, max_retries, breaker_threshold, cooldown):
self.providers = providers
def complete(self, prompt):
p = self.providers[0]
return {"text": p.complete(prompt), "provider": p.name, "attempts": 1}
Run executes the public tests. Submit grades against public and hidden tests.
Implement Gateway(providers, clock, sleep, max_retries, breaker_threshold, cooldown) with
complete(prompt) -> {"text", "provider", "attempts"}. providers is a list of objects with a name and
a complete(prompt) method that returns text or raises ProviderError (provided) with a status.
Policy:
cooldown
seconds ago by clock()).max_retries times, sleeping
0.5 × 2**i seconds before retry i (0, 1, …) using sleep. Then move on to the next provider.breaker_threshold, the circuit opens (stop using that provider
immediately, even mid-retries). A provider whose cooldown has passed is tried again; a success closes
its circuit, a failure re-opens it.BadRequest (provided) at once — don't try other providers.AllProvidersFailed (provided).attempts counts every provider call made for this prompt. The harness replays prompts with scripted
provider failures; each provider call takes 1 second on the fake clock.
Implement Gateway. Input: providers, clock, sleep, max_retries: int, breaker_threshold: int, cooldown: float. Returns: a class.
Prompt a: primary fails, sleep 0.5, fails again (retries exhausted), backup answers. Prompt b: primary has 2 failures (below 3) and its script is empty now, so it answers.
Two failures open primary's circuit; backup's 400 raises BadRequest for x. For y, primary is still open (skipped) and backup has one failure (below 2), so it is tried and answers.
This code runs before yours (fake clients, clocks and the test harness). You can use its names; don't edit them.
class ProviderError(Exception):
def __init__(self, status):
super().__init__(f"HTTP {status}")
self.status = status
class BadRequest(Exception):
pass
class AllProvidersFailed(Exception):
pass
class FakeProvider:
def __init__(self, name, script, now):
self.name, self.script, self.now, self.calls = name, list(script), now, 0
def complete(self, prompt):
self.calls += 1
self.now["t"] += 1.0
outcome = self.script.pop(0) if self.script else "ok"
if outcome != "ok":
raise ProviderError(outcome)
return f"{self.name}:{prompt}"
def __harness__(cls, scripts, prompts, max_retries, threshold, cooldown):
now = {"t": 0.0}
providers = [FakeProvider(name, script, now) for name, script in scripts]
def sleep(seconds):
now["t"] += seconds
gateway = cls(providers, lambda: now["t"], sleep, max_retries, threshold, cooldown)
results = []
for p in prompts:
try:
r = gateway.complete(p)
results.append([r["provider"], r["attempts"]])
except BadRequest:
results.append("bad_request")
except AllProvidersFailed:
results.append("all_failed")
return {"results": results, "calls": {p.name: p.calls for p in providers}, "clock": round(now["t"], 3)}
class Gateway:
def __init__(self, providers, clock, sleep, max_retries, breaker_threshold, cooldown):
self.providers = providers
def complete(self, prompt):
p = self.providers[0]
return {"text": p.complete(prompt), "provider": p.name, "attempts": 1}
Run executes the public tests. Submit grades against public and hidden tests.