Make allocation strategy for wasmtime configurable (#546)

Author: aumetra

crates/kitsune-config/src/mrf.rs

@@ -2,6 +2,14 @@ use serde::{Deserialize, Serialize};
 use smol_str::SmolStr;
 use std::{collections::HashMap, num::NonZeroUsize};
 
+#[derive(Clone, Debug, Default, Deserialize, Serialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum AllocationStrategy {
+    OnDemand,
+    #[default]
+    Pooling,
+}
+
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub struct ArtifactCache {
     pub path: SmolStr,
@@ -30,6 +38,8 @@ pub enum KvStorage {
 #[derive(Clone, Debug, Deserialize, Serialize)]
 #[serde(rename_all = "kebab-case")]
 pub struct Configuration {
+    #[serde(default)]
+    pub allocation_strategy: AllocationStrategy,
     pub artifact_cache: Option<ArtifactCache>,
     pub module_dir: SmolStr,
     pub module_config: HashMap<SmolStr, SmolStr>,

crates/kitsune-wasm-mrf/src/lib.rs

@@ -10,7 +10,7 @@ use color_eyre::{eyre, Section};
 use fred::{clients::RedisPool, interfaces::ClientLike, types::RedisConfig};
 use futures_util::{stream::FuturesUnordered, Stream, TryFutureExt, TryStreamExt};
 use kitsune_config::mrf::{
-    Configuration as MrfConfiguration, FsKvStorage, KvStorage, RedisKvStorage,
+    AllocationStrategy, Configuration as MrfConfiguration, FsKvStorage, KvStorage, RedisKvStorage,
 };
 use kitsune_derive::kitsune_service;
 use kitsune_error::Error;
@@ -171,9 +171,14 @@ impl MrfService {
             }
         };
 
+        let allocation_strategy = match config.allocation_strategy {
+            AllocationStrategy::OnDemand => InstanceAllocationStrategy::OnDemand,
+            AllocationStrategy::Pooling => InstanceAllocationStrategy::pooling(),
+        };
+
         let mut engine_config = Config::new();
         engine_config
-            .allocation_strategy(InstanceAllocationStrategy::pooling())
+            .allocation_strategy(allocation_strategy)
             .async_support(true)
             .wasm_component_model(true);
 

docs/src/configuring/mrf.md

@@ -14,6 +14,19 @@ For example, you can use it to:
 
 ## Configuration
 
+### `allocation-strategy`
+
+⚠ You usually don't need to touch this setting!
+
+It has two possible values:
+
+- `on-demand`
+- `pooling`
+
+By default it is set to `pooling` which will offer the best throughput since Kitsune instantiates short-lived WASM modules, where pooled allocation can improve performance.
+
+If Kitsune crashes on startup complaining about `failed to create stack pool mapping`, you might want to try changing this setting to `on-demand`.
+
 ### `module-dir`
 
 This configuration option tells Kitsune where to scan for WASM modules to load and compile.
@@ -40,7 +53,7 @@ path = "./artifact-cache"
 
 ### `storage`
 
-Kitsune provides MRF modules with scoped key-value storages to allow them to persist data across runs for things like counters or spam lists.  
+Kitsune provides MRF modules with scoped key-value storages to allow them to persist data across runs for things like counters or spam lists.
 
 We provide multiple backends here: