383 lines
15 KiB
Rust
383 lines
15 KiB
Rust
use crate::tree::Tree;
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use actix_web::http::header::{HeaderValue, CONTENT_TYPE};
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use actix_web::{HttpRequest, HttpResponse};
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use bytes::Bytes;
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use futures_util::{StreamExt, TryStreamExt};
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use log::{debug, info};
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use std::collections::HashMap;
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use std::fmt::Debug;
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use std::sync::atomic::AtomicUsize;
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use std::sync::{Arc, Mutex};
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use std::thread;
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use std::time::Duration;
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#[derive(Debug)]
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pub enum Router {
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RoundRobin {
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worker_urls: Vec<String>,
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current_index: AtomicUsize,
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},
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Random {
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worker_urls: Vec<String>,
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},
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CacheAware {
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/*
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Cache-Aware Load Balancing Router
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This router combines two strategies to optimize both cache utilization and request distribution:
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1. Cache-Aware Routing (Approximate Tree)
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2. Load Balancing (Shortest Queue with Balance Thresholds)
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The router dynamically switches between these strategies based on load conditions:
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- Uses load balancing when the system is imbalanced
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- Uses cache-aware routing when the system is balanced
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A system is considered imbalanced if both conditions are met:
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1. (max - min) > abs_threshold
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2. max > rel_threshold * min
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Strategy Details:
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1. Cache-Aware Routing (Approximate Tree)
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-------------------------------------------
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This strategy maintains an approximate radix tree for each worker based on request history,
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eliminating the need for direct cache state queries. The tree stores raw text characters
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instead of token IDs to avoid tokenization overhead.
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Process:
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a. For each request, find the worker with the highest prefix match
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b. If match rate > cache_threshold:
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Route to the worker with highest match (likely has relevant data cached)
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c. If match rate ≤ cache_threshold:
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Route to the worker with smallest tree size (most available cache capacity)
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d. Background maintenance:
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Periodically evict least recently used leaf nodes to prevent memory overflow
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2. Load Balancing (Shortest Queue)
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-------------------------------------------
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This strategy tracks pending request counts per worker and routes new requests
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to the least busy worker when the system is detected to be imbalanced.
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Configuration Parameters:
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------------------------
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1. cache_threshold: (float, 0.0 to 1.0)
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Minimum prefix match ratio to use highest-match routing.
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Below this threshold, routes to worker with most available cache space.
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2. balance_abs_threshold: (integer)
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Absolute difference threshold for load imbalance detection.
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System is potentially imbalanced if (max_load - min_load) > abs_threshold
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3. balance_rel_threshold: (float)
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Relative ratio threshold for load imbalance detection.
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System is potentially imbalanced if max_load > min_load * rel_threshold
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Used in conjunction with abs_threshold to determine final imbalance state.
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4. eviction_interval_secs: (integer)
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Interval between LRU eviction cycles for the approximate trees.
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5. max_tree_size: (integer)
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Maximum nodes per tree. When exceeded, LRU leaf nodes are evicted
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during the next eviction cycle.
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*/
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worker_urls: Vec<String>,
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tree: Arc<Mutex<Tree>>,
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running_queue: Arc<Mutex<HashMap<String, usize>>>,
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processed_queue: Arc<Mutex<HashMap<String, usize>>>,
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cache_threshold: f32,
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balance_abs_threshold: usize,
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balance_rel_threshold: f32,
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_eviction_thread: Option<thread::JoinHandle<()>>,
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},
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}
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#[derive(Debug)]
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pub enum PolicyConfig {
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RandomConfig,
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RoundRobinConfig,
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CacheAwareConfig {
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cache_threshold: f32,
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balance_abs_threshold: usize,
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balance_rel_threshold: f32,
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eviction_interval_secs: u64,
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max_tree_size: usize,
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},
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}
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fn get_text_from_request(body: &Bytes, route: &str) -> String {
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// convert body to json
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let json = serde_json::from_slice::<serde_json::Value>(body).unwrap();
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if route == "generate" {
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// get the "text" field
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let text = json.get("text").and_then(|t| t.as_str()).unwrap_or("");
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return text.to_string();
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} else if route == "v1/chat/completions" {
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// get the messages field as raw text
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if let Some(messages) = json.get("messages") {
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// Convert messages back to a string, preserving all JSON formatting
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return serde_json::to_string(messages).unwrap_or_default();
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}
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} else if route == "v1/completions" {
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let prompt = json.get("prompt").and_then(|t| t.as_str()).unwrap_or("");
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return prompt.to_string();
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}
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return "".to_string();
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}
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impl Router {
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pub fn new(worker_urls: Vec<String>, policy_config: PolicyConfig) -> Self {
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match policy_config {
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PolicyConfig::RandomConfig => Router::Random { worker_urls },
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PolicyConfig::RoundRobinConfig => Router::RoundRobin {
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worker_urls,
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current_index: std::sync::atomic::AtomicUsize::new(0),
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},
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PolicyConfig::CacheAwareConfig {
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cache_threshold,
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balance_abs_threshold,
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balance_rel_threshold,
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eviction_interval_secs,
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max_tree_size,
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} => {
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let mut running_queue = HashMap::new();
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for url in &worker_urls {
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running_queue.insert(url.clone(), 0);
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}
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let mut processed_queue = HashMap::new();
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for url in &worker_urls {
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processed_queue.insert(url.clone(), 0);
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}
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let tree = Arc::new(Mutex::new(Tree::new()));
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let running_queue = Arc::new(Mutex::new(running_queue));
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let processed_queue = Arc::new(Mutex::new(processed_queue));
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// Create background eviction thread
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let tree_clone = Arc::clone(&tree);
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let processed_queue_clone = Arc::clone(&processed_queue);
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let running_queue_clone = Arc::clone(&running_queue);
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let eviction_thread = thread::spawn(move || {
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loop {
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// Sleep for the specified interval
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thread::sleep(Duration::from_secs(eviction_interval_secs));
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let locked_tree_clone = tree_clone.lock().unwrap();
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// Run eviction
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locked_tree_clone.evict_tenant_data(max_tree_size);
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// Print the process queue
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let locked_processed_queue = processed_queue_clone.lock().unwrap();
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info!("Processed Queue: {:?}", locked_processed_queue);
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// Print the running queue
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let locked_running_queue = running_queue_clone.lock().unwrap();
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info!("Running Queue: {:?}", locked_running_queue);
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}
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});
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for url in &worker_urls {
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tree.lock().unwrap().insert(&"".to_string(), url);
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}
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Router::CacheAware {
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worker_urls,
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tree,
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running_queue,
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processed_queue,
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cache_threshold,
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balance_abs_threshold,
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balance_rel_threshold,
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_eviction_thread: Some(eviction_thread),
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}
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}
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}
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}
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pub fn get_first(&self) -> Option<String> {
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match self {
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Router::RoundRobin { worker_urls, .. }
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| Router::Random { worker_urls }
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| Router::CacheAware { worker_urls, .. } => {
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if worker_urls.is_empty() {
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None
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} else {
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Some(worker_urls[0].clone())
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}
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}
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}
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}
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pub async fn dispatch(
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&self,
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client: &reqwest::Client,
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req: HttpRequest,
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body: Bytes,
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route: &str,
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) -> HttpResponse {
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let text = get_text_from_request(&body, route);
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let worker_url = match self {
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Router::RoundRobin {
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worker_urls,
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current_index,
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} => {
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let idx = current_index
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.fetch_update(
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std::sync::atomic::Ordering::SeqCst,
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std::sync::atomic::Ordering::SeqCst,
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|x| Some((x + 1) % worker_urls.len()),
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)
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.unwrap();
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worker_urls[idx].clone()
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}
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Router::Random { worker_urls } => {
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worker_urls[rand::random::<usize>() % worker_urls.len()].clone()
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}
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Router::CacheAware {
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worker_urls,
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tree,
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running_queue,
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processed_queue,
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cache_threshold,
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balance_abs_threshold,
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balance_rel_threshold,
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..
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} => {
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// TODO: delay scheduling if cache hit rate is high because it may cause imbalance. prioritize low hit rate ones
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let tree = tree.lock().unwrap();
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let mut running_queue = running_queue.lock().unwrap();
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// Get current load statistics
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let max_load = *running_queue.values().max().unwrap_or(&0);
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let min_load = *running_queue.values().min().unwrap_or(&0);
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// Load is considered imbalanced if:
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// 1. (max - min) > abs_threshold AND
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// 2. max > rel_threshold * min
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let is_imbalanced = max_load.saturating_sub(min_load) > *balance_abs_threshold
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&& (max_load as f32) > (min_load as f32 * balance_rel_threshold);
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let selected_url = if is_imbalanced {
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// Log load balancing trigger and current queue state
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info!(
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"Load balancing triggered due to workload imbalance:\n\
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Max load: {}, Min load: {}\n\
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Current running queue: {:?}",
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max_load, min_load, running_queue
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);
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// Use shortest queue routing when load is imbalanced
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running_queue
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.iter()
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.min_by_key(|(_url, &count)| count)
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.map(|(url, _)| url.clone())
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.unwrap_or_else(|| worker_urls[0].clone())
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} else {
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// Use cache-aware routing when load is balanced
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let (matched_text, matched_worker) = tree.prefix_match(&text);
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let matched_rate =
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matched_text.chars().count() as f32 / text.chars().count() as f32;
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if matched_rate > *cache_threshold {
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matched_worker.to_string()
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} else {
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tree.get_smallest_tenant()
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}
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};
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// Update queues and tree
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*running_queue.get_mut(&selected_url).unwrap() += 1;
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*processed_queue
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.lock()
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.unwrap()
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.get_mut(&selected_url)
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.unwrap() += 1;
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tree.insert(&text, &selected_url);
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selected_url
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}
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};
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let is_stream = serde_json::from_slice::<serde_json::Value>(&body)
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.map(|v| v.get("stream").and_then(|s| s.as_bool()).unwrap_or(false))
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.unwrap_or(false);
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let res = match client
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.post(format!("{}/{}", worker_url.clone(), route))
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.header(
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"Content-Type",
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req.headers()
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.get("Content-Type")
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.and_then(|h| h.to_str().ok())
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.unwrap_or("application/json"),
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)
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.body(body.to_vec())
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.send()
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.await
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{
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Ok(res) => res,
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Err(_) => return HttpResponse::InternalServerError().finish(),
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};
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let status = actix_web::http::StatusCode::from_u16(res.status().as_u16())
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.unwrap_or(actix_web::http::StatusCode::INTERNAL_SERVER_ERROR);
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if !is_stream {
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// For non-streaming requests, get response first
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let response = match res.bytes().await {
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Ok(body) => HttpResponse::build(status).body(body.to_vec()),
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Err(_) => HttpResponse::InternalServerError().finish(),
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};
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// Then decrement running queue counter if using CacheAware
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if let Router::CacheAware { running_queue, .. } = self {
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if let Ok(mut queue) = running_queue.lock() {
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if let Some(count) = queue.get_mut(&worker_url) {
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*count = count.saturating_sub(1);
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}
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}
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}
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response
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} else if let Router::CacheAware { running_queue, .. } = self {
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let running_queue = Arc::clone(running_queue);
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let worker_url = worker_url.clone();
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HttpResponse::build(status)
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.insert_header((CONTENT_TYPE, HeaderValue::from_static("text/event-stream")))
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.streaming(
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res.bytes_stream()
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.map_err(|_| {
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actix_web::error::ErrorInternalServerError("Failed to read stream")
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})
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.inspect(move |bytes| {
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let bytes = bytes.as_ref().unwrap();
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if bytes
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.as_ref()
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.windows(12)
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.any(|window| window == b"data: [DONE]")
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{
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let mut locked_queue = running_queue.lock().unwrap();
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let count = locked_queue.get_mut(&worker_url).unwrap();
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*count = count.saturating_sub(1);
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debug!("streaming is done!!")
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}
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}),
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)
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} else {
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HttpResponse::build(status)
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.insert_header((CONTENT_TYPE, HeaderValue::from_static("text/event-stream")))
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.streaming(res.bytes_stream().map_err(|_| {
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actix_web::error::ErrorInternalServerError("Failed to read stream")
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}))
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}
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}
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}
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