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[router] Add retries based fault tolerance #2452

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Dec 11, 2024
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56 changes: 55 additions & 1 deletion rust/py_test/test_launch_server.py
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

import requests

from sglang.srt.utils import kill_process_tree
from sglang.test.run_eval import run_eval
from sglang.test.test_utils import (
DEFAULT_MODEL_NAME_FOR_TEST,
Expand Down Expand Up @@ -182,7 +183,7 @@ def test_2_add_and_remove_worker(self):
timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
policy="round_robin", # use round robin to make sure every worker processes requests
)
# 1. start a worker, and wait until it is healthy
# 1. start a worker
port = find_available_port()
worker_url = f"http://127.0.0.1:{port}"
worker_process = popen_launch_server(
Expand Down Expand Up @@ -226,6 +227,59 @@ def test_2_add_and_remove_worker(self):
msg = f"MMLU test {'passed' if passed else 'failed'} with score {score:.3f} (threshold: {THRESHOLD})"
self.assertGreaterEqual(score, THRESHOLD, msg)

def test_3_lazy_fault_tolerance(self):
print("Running test_3_lazy_fault_tolerance...")
# DP size = 1
self.process = popen_launch_router(
self.model,
self.base_url,
dp_size=1,
timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
policy="round_robin",
)

# 1. start a worker
port = find_available_port()
worker_url = f"http://127.0.0.1:{port}"
worker_process = popen_launch_server(
self.model, worker_url, DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH
)
self.other_process.append(worker_process)

# 2. use /add_worker api to add it the the router. It will be used by router after it is healthy
with requests.Session() as session:
response = session.post(f"{self.base_url}/add_worker?url={worker_url}")
print(f"status code: {response.status_code}, response: {response.text}")
self.assertEqual(response.status_code, 200)

# Start a thread to kill the worker after 10 seconds to mimic abrupt worker failure
def kill_worker():
time.sleep(10)
kill_process_tree(worker_process.pid)
print("Worker process killed")

import threading

kill_thread = threading.Thread(target=kill_worker)
kill_thread.daemon = True
kill_thread.start()

# 3. run mmlu
args = SimpleNamespace(
base_url=self.base_url,
model=self.model,
eval_name="mmlu",
num_examples=256,
num_threads=32,
temperature=0.1,
)
metrics = run_eval(args)
score = metrics["score"]
THRESHOLD = 0.65
passed = score >= THRESHOLD
msg = f"MMLU test {'passed' if passed else 'failed'} with score {score:.3f} (threshold: {THRESHOLD})"
self.assertGreaterEqual(score, THRESHOLD, msg)


if __name__ == "__main__":
unittest.main()
98 changes: 89 additions & 9 deletions rust/src/router.rs
Original file line number Diff line number Diff line change
Expand Up @@ -274,10 +274,49 @@ impl Router {
}

pub async fn route_to_first(&self, client: &reqwest::Client, route: &str) -> HttpResponse {
match self.select_first_worker() {
Ok(worker_url) => self.send_request(client, &worker_url, route).await,
Err(e) => HttpResponse::InternalServerError().body(e),
const MAX_REQUEST_RETRIES: u32 = 3;
const MAX_TOTAL_RETRIES: u32 = 6;
let mut total_retries = 0;

while total_retries < MAX_TOTAL_RETRIES {
match self.select_first_worker() {
Ok(worker_url) => {
let mut request_retries = 0;

// Try the same worker multiple times
while request_retries < MAX_REQUEST_RETRIES {
if total_retries >= 1 {
info!("Retrying request after {} failed attempts", total_retries);
}

let response = self.send_request(client, &worker_url, route).await;

if response.status().is_success() {
return response;
}

warn!(
"Request to {} failed (attempt {}/{})",
worker_url,
request_retries + 1,
MAX_REQUEST_RETRIES
);

request_retries += 1;
total_retries += 1;

if request_retries == MAX_REQUEST_RETRIES {
warn!("Removing failed worker: {}", worker_url);
self.remove_worker(&worker_url);
break;
}
}
}
Err(e) => return HttpResponse::InternalServerError().body(e),
}
}

HttpResponse::InternalServerError().body("All retry attempts failed")
}

fn get_text_from_request(&self, body: &Bytes, route: &str) -> String {
Expand Down Expand Up @@ -488,9 +527,46 @@ impl Router {
body: &Bytes,
route: &str,
) -> HttpResponse {
let worker_url = self.select_generate_worker(&body, route);
self.send_generate_request(client, req, body, route, &worker_url)
.await
const MAX_REQUEST_RETRIES: u32 = 3;
const MAX_TOTAL_RETRIES: u32 = 6;
let mut total_retries = 0;

while total_retries < MAX_TOTAL_RETRIES {
let worker_url = self.select_generate_worker(body, route);
let mut request_retries = 0;

// Try the same worker multiple times
while request_retries < MAX_REQUEST_RETRIES {
if total_retries >= 1 {
info!("Retrying request after {} failed attempts", total_retries);
}
let response = self
.send_generate_request(client, req, body, route, &worker_url)
.await;

if response.status().is_success() {
return response;
}

warn!(
"Generate request to {} failed (attempt {}/{})",
worker_url,
request_retries + 1,
MAX_REQUEST_RETRIES
);

request_retries += 1;
total_retries += 1;

if request_retries == MAX_REQUEST_RETRIES {
warn!("Removing failed worker: {}", worker_url);
self.remove_worker(&worker_url);
break;
}
}
}

HttpResponse::InternalServerError().body("All retry attempts failed")
}

pub async fn add_worker(&self, worker_url: &str) -> Result<String, String> {
Expand Down Expand Up @@ -590,9 +666,13 @@ impl Router {
| Router::Random { worker_urls }
| Router::CacheAware { worker_urls, .. } => {
let mut urls = worker_urls.write().unwrap();
let index = urls.iter().position(|url| url == &worker_url).unwrap();
urls.remove(index);
info!("Removed worker: {}", worker_url);
if let Some(index) = urls.iter().position(|url| url == &worker_url) {
urls.remove(index);
info!("Removed worker: {}", worker_url);
} else {
warn!("Worker {} not found, skipping removal", worker_url);
return;
}
}
}

Expand Down
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