feat(wasmtime) expose cache_config directive

This adds support for `wasmtime { cache_config <config.toml>; }`, for enabling disk caching of ahead-of-time compilation of .wasm files. This should alleviate noticeable CPU spikes when starting up workers using Wasmtime and Wasm modules larger than a few megabytes.
Kong · Apr 24, 2024 · 9ef2ec5 · 9ef2ec5
1 parent bb139e1
commit 9ef2ec5
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Showing 4 changed files with 194 additions and 40 deletions.
diff --git a/src/wasm/ngx_wasm_core_module.c b/src/wasm/ngx_wasm_core_module.c
@@ -52,6 +52,14 @@ static ngx_command_t  ngx_wasm_core_commands[] = {
       0,
       NULL },
 
+    { ngx_string("cache_config"),
+      NGX_WASMTIME_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_str_slot,
+      NGX_WA_WASM_CONF_OFFSET,
+      offsetof(ngx_wasm_core_conf_t, vm_conf)
+      + offsetof(ngx_wavm_conf_t, cache_config),
+      NULL },
+
     { ngx_string("compiler"),
       NGX_WASM_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_str_slot,

diff --git a/src/wasm/wrt/ngx_wrt.h b/src/wasm/wrt/ngx_wrt.h
@@ -16,6 +16,7 @@ typedef struct ngx_wavm_instance_s  ngx_wavm_instance_t;
 typedef struct {
     const ngx_str_t               *vm_name;
     const ngx_str_t               *runtime_name;
+    ngx_str_t                      cache_config;
     ngx_str_t                      compiler;
     ngx_flag_t                     backtraces;
     ngx_array_t                    flags;

diff --git a/src/wasm/wrt/ngx_wrt_wasmtime.c b/src/wasm/wrt/ngx_wrt_wasmtime.c
@@ -8,15 +8,20 @@
 #include <ngx_wasi.h>
 
 
-#define NGX_WRT_WASMTIME_STACK_NARGS  10
-#define NGX_WRT_WASMTIME_STACK_NRETS  10
+#define NGX_WRT_WASMTIME_STACK_NARGS     10
+#define NGX_WRT_WASMTIME_STACK_NRETS     10
+#define NGX_WRT_WASMTIME_CONFIG_ERR_LEN  255
 
 
 typedef void (*wasmtime_config_set_int_pt)(wasm_config_t *config,
     uint64_t value);
 typedef void (*wasmtime_config_set_bool_pt)(wasm_config_t *config, bool value);
 
 
+static u_char * ngx_wasmtime_log_handler(ngx_wrt_res_t *res, u_char *buf,
+    size_t len);
+
+
 static ngx_int_t
 size_flag_handler(wasm_config_t *config, ngx_str_t *name, ngx_str_t *value,
     ngx_log_t *log, void *wrt_setter)
@@ -129,7 +134,10 @@ profiler_flag_handler(wasm_config_t *config, ngx_str_t *name, ngx_str_t *value,
 static wasm_config_t *
 ngx_wasmtime_init_conf(ngx_wavm_conf_t *conf, ngx_log_t *log)
 {
-    wasm_config_t  *config;
+    wasm_config_t     *config;
+    char              *pathname;
+    u_char            *errmsg;
+    wasmtime_error_t  *err;
 #if 0
     wasm_name_t        msg;
     wasmtime_error_t  *err = NULL;
@@ -160,6 +168,39 @@ ngx_wasmtime_init_conf(ngx_wavm_conf_t *conf, ngx_log_t *log)
     wasmtime_config_static_memory_maximum_size_set(config, 0);
 #endif
 
+    if (conf->cache_config.len) {
+        ngx_wavm_log_error(NGX_LOG_INFO, log, NULL,
+                           "setting wasmtime cache config file: \"%V\"",
+                           &conf->cache_config);
+
+        pathname = ngx_calloc(conf->cache_config.len + 1, log);
+        if (pathname == NULL) {
+            goto error;
+        }
+
+        ngx_memcpy(pathname, conf->cache_config.data, conf->cache_config.len);
+
+        err = wasmtime_config_cache_config_load(config, pathname);
+
+        ngx_free(pathname);
+
+        if (err) {
+            errmsg = ngx_calloc(NGX_WRT_WASMTIME_CONFIG_ERR_LEN + 1, log);
+            if (errmsg == NULL) {
+                goto error;
+            }
+
+            ngx_wasmtime_log_handler((ngx_wrt_res_t *) err, errmsg,
+                                     NGX_WRT_WASMTIME_CONFIG_ERR_LEN);
+
+            ngx_log_error(NGX_LOG_EMERG, log, 0,
+                          "failed configuring wasmtime cache; %s",
+                          errmsg);
+
+            goto error;
+        }
+    }
+
     if (conf->compiler.len) {
         if (ngx_str_eq(conf->compiler.data, conf->compiler.len,
                        "auto", -1))