rename the method to get a permit and use it in all search requests

meilisearch/src/lib.rs

@@ -13,9 +13,10 @@ pub mod search_queue;
 
 use std::fs::File;
 use std::io::{BufReader, BufWriter};
+use std::num::NonZeroUsize;
 use std::path::Path;
 use std::sync::Arc;
-use std::thread;
+use std::thread::{self, available_parallelism};
 use std::time::Duration;
 
 use actix_cors::Cors;
@@ -39,6 +40,7 @@ use meilisearch_types::versioning::{check_version_file, create_version_file};
 use meilisearch_types::{compression, milli, VERSION_FILE_NAME};
 pub use option::Opt;
 use option::ScheduleSnapshot;
+use search_queue::SearchQueue;
 use tracing::{error, info_span};
 use tracing_subscriber::filter::Targets;
 
@@ -470,10 +472,15 @@ pub fn configure_data(
     (logs_route, logs_stderr): (LogRouteHandle, LogStderrHandle),
     analytics: Arc<dyn Analytics>,
 ) {
+    let search_queue = SearchQueue::new(
+        opt.experimental_search_queue_size,
+        available_parallelism().unwrap_or(NonZeroUsize::new(2).unwrap()),
+    );
     let http_payload_size_limit = opt.http_payload_size_limit.get_bytes() as usize;
     config
         .app_data(index_scheduler)
         .app_data(auth)
+        .app_data(web::Data::new(search_queue))
         .app_data(web::Data::from(analytics))
         .app_data(web::Data::new(logs_route))
         .app_data(web::Data::new(logs_stderr))

meilisearch/src/routes/indexes/facet_search.rs

@@ -17,6 +17,7 @@ use crate::search::{
     DEFAULT_CROP_LENGTH, DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG,
     DEFAULT_HIGHLIGHT_PRE_TAG, DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
 };
+use crate::search_queue::SearchQueue;
 
 pub fn configure(cfg: &mut web::ServiceConfig) {
     cfg.service(web::resource("").route(web::post().to(search)));
@@ -48,6 +49,7 @@ pub struct FacetSearchQuery {
 
 pub async fn search(
     index_scheduler: GuardedData<ActionPolicy<{ actions::SEARCH }>, Data<IndexScheduler>>,
+    search_queue: Data<SearchQueue>,
     index_uid: web::Path<String>,
     params: AwebJson<FacetSearchQuery, DeserrJsonError>,
     req: HttpRequest,
@@ -71,6 +73,7 @@ pub async fn search(
 
     let index = index_scheduler.index(&index_uid)?;
     let features = index_scheduler.features();
+    let _permit = search_queue.try_get_search_permit().await?;
     let search_result = tokio::task::spawn_blocking(move || {
         perform_facet_search(&index, search_query, facet_query, facet_name, features)
     })

meilisearch/src/routes/indexes/search.rs

@@ -23,6 +23,7 @@ use crate::search::{
     DEFAULT_CROP_LENGTH, DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG,
     DEFAULT_HIGHLIGHT_PRE_TAG, DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET, DEFAULT_SEMANTIC_RATIO,
 };
+use crate::search_queue::SearchQueue;
 
 pub fn configure(cfg: &mut web::ServiceConfig) {
     cfg.service(
@@ -182,6 +183,7 @@ fn fix_sort_query_parameters(sort_query: &str) -> Vec<String> {
 
 pub async fn search_with_url_query(
     index_scheduler: GuardedData<ActionPolicy<{ actions::SEARCH }>, Data<IndexScheduler>>,
+    search_queue: web::Data<SearchQueue>,
     index_uid: web::Path<String>,
     params: AwebQueryParameter<SearchQueryGet, DeserrQueryParamError>,
     req: HttpRequest,
@@ -204,6 +206,7 @@ pub async fn search_with_url_query(
 
     let distribution = embed(&mut query, index_scheduler.get_ref(), &index).await?;
 
+    let _permit = search_queue.try_get_search_permit().await?;
     let search_result =
         tokio::task::spawn_blocking(move || perform_search(&index, query, features, distribution))
             .await?;
@@ -220,6 +223,7 @@ pub async fn search_with_url_query(
 
 pub async fn search_with_post(
     index_scheduler: GuardedData<ActionPolicy<{ actions::SEARCH }>, Data<IndexScheduler>>,
+    search_queue: web::Data<SearchQueue>,
     index_uid: web::Path<String>,
     params: AwebJson<SearchQuery, DeserrJsonError>,
     req: HttpRequest,
@@ -243,6 +247,7 @@ pub async fn search_with_post(
 
     let distribution = embed(&mut query, index_scheduler.get_ref(), &index).await?;
 
+    let _permit = search_queue.try_get_search_permit().await?;
     let search_result =
         tokio::task::spawn_blocking(move || perform_search(&index, query, features, distribution))
             .await?;

meilisearch/src/routes/multi_search.rs

@@ -17,6 +17,7 @@ use crate::routes::indexes::search::embed;
 use crate::search::{
     add_search_rules, perform_search, SearchQueryWithIndex, SearchResultWithIndex,
 };
+use crate::search_queue::SearchQueue;
 
 pub fn configure(cfg: &mut web::ServiceConfig) {
     cfg.service(web::resource("").route(web::post().to(SeqHandler(multi_search_with_post))));
@@ -35,6 +36,7 @@ pub struct SearchQueries {
 
 pub async fn multi_search_with_post(
     index_scheduler: GuardedData<ActionPolicy<{ actions::SEARCH }>, Data<IndexScheduler>>,
+    search_queue: Data<SearchQueue>,
     params: AwebJson<SearchQueries, DeserrJsonError>,
     req: HttpRequest,
     analytics: web::Data<dyn Analytics>,
@@ -44,6 +46,10 @@ pub async fn multi_search_with_post(
     let mut multi_aggregate = MultiSearchAggregator::from_queries(&queries, &req);
     let features = index_scheduler.features();
 
+    // Since we don't want to process half of the search requests and then get a permit refused
+    // we're going to get one permit for the whole duration of the multi-search request.
+    let _permit = search_queue.try_get_search_permit().await?;
+
     // Explicitly expect a `(ResponseError, usize)` for the error type rather than `ResponseError` only,
     // so that `?` doesn't work if it doesn't use `with_index`, ensuring that it is not forgotten in case of code
     // changes.

meilisearch/src/search_queue.rs

@@ -1,4 +1,4 @@
-use std::time::Duration;
+use std::{num::NonZeroUsize, time::Duration};
 
 use rand::{rngs::StdRng, Rng, SeedableRng};
 use tokio::sync::{mpsc, oneshot};
@@ -24,7 +24,7 @@ impl Drop for Permit {
 }
 
 impl SearchQueue {
-    pub fn new(capacity: usize, paralellism: usize) -> Self {
+    pub fn new(capacity: usize, paralellism: NonZeroUsize) -> Self {
         // We can make the search requests wait until we're available.
         // they're going to wait anyway right after, so let's not allocate any
         // RAM by keeping a capacity of 1.
@@ -35,21 +35,21 @@ impl SearchQueue {
 
     async fn run(
         capacity: usize,
-        parallelism: usize,
+        parallelism: NonZeroUsize,
         mut receive_new_searches: mpsc::Receiver<oneshot::Sender<Permit>>,
     ) {
         let mut queue: Vec<oneshot::Sender<Permit>> = Default::default();
         let mut rng: StdRng = StdRng::from_entropy();
-        let mut searches_running = 0;
+        let mut searches_running: usize = 0;
         // by having a capacity of parallelism we ensures that every time a search finish it can release its RAM asap
-        let (sender, mut search_finished) = mpsc::channel(parallelism);
+        let (sender, mut search_finished) = mpsc::channel(parallelism.into());
 
         loop {
             tokio::select! {
                 search_request = receive_new_searches.recv() => {
                     let search_request = search_request.unwrap();
                     println!("queue contains {} elements and already running {}", queue.len(), searches_running);
-                    if searches_running < parallelism && queue.is_empty() {
+                    if searches_running < usize::from(parallelism) && queue.is_empty() {
                         println!("We can process the search straight away");
                         searches_running += 1;
                         // if the search requests die it's not a hard error on our side
@@ -78,7 +78,7 @@ impl SearchQueue {
         }
     }
 
-    pub async fn register_search(&self) -> Result<Permit, MeilisearchHttpError> {
+    pub async fn try_get_search_permit(&self) -> Result<Permit, MeilisearchHttpError> {
         let (sender, receiver) = oneshot::channel();
         self.sender.send(sender).await.map_err(|_| MeilisearchHttpError::SearchLimiterIsDown)?;
         receiver.await.map_err(|_| {