feat(wasm): support directive for general shm_kv entry

WasmX supports using non-namespaced entries in proxy-wasm `get_shared_data`
and `set_shared_data`. For this, one needs to define a no-namespaced shm_kv
using the `shm_kv * <size>` directive. This commit adds
`nginx_wasm_main_shm_kv` as a supported option alongside the existing
`nginx_wasm_main_shm_kv_<namespace>` entries, for definition of the
non-namespaced `shm_kv`.

changelog/unreleased/kong/feat-wasm-general-shm-kv.yml

@@ -0,0 +1,6 @@
+message: |
+   Introduce `nginx_wasm_main_shm_kv` configuration entry, which enables
+   Wasm filters to use the Proxy-Wasm operations `get_shared_data` and
+   `set_shared_data` without namespaced keys.
+type: feature
+scope: Configuration

kong.conf.default

@@ -732,7 +732,7 @@
 
 #mem_cache_size = 128m           # Size of each of the two shared memory caches
                                  # for traditional mode database entities
-                                 # and runtime data, `kong_core_cache` and 
+                                 # and runtime data, `kong_core_cache` and
                                  # `kong_cache`.
                                  #
                                  # The accepted units are `k` and `m`, with a minimum
@@ -2065,9 +2065,16 @@
 # The following namespaces are supported:
 #
 # - `nginx_wasm_<directive>`: Injects `<directive>` into the `wasm {}` block.
+# - `nginx_wasm_shm_kv`: Injects `shm_kv *` into the `wasm {}` block,
+#   allowing operators to define a general memory zone which is usable by
+#   the `get_shared_data`/`set_shared_data` Proxy-Wasm SDK functions as
+#   an in-memory key-value store of data shareable across filters.
 # - `nginx_wasm_shm_kv_<name>`: Injects `shm_kv <name>` into the `wasm {}` block,
 #   allowing operators to define custom shared memory zones which are usable by
-#   the `get_shared_data`/`set_shared_data` Proxy-Wasm SDK functions.
+#   the `get_shared_data`/`set_shared_data` Proxy-Wasm SDK functions as
+#   separate namespaces in the `"<name>/<key>"` format.
+#   For using these functions with non-namespaced keys, the Nginx template needs
+#   a `shm_kv *` entry, which can be defined using `nginx_wasm_shm_kv`.
 # - `nginx_wasm_wasmtime_<flag>`: Injects `flag <flag>` into the `wasmtime {}`
 #   block, allowing various Wasmtime-specific flags to be set.
 # - `nginx_<http|proxy>_<directive>`: Injects `<directive>` into the

kong/conf_loader/constants.lua

@@ -305,6 +305,8 @@ local CONF_PARSERS = {
     },
   },
 
+  nginx_wasm_main_shm_kv = { typ = "string" },
+
   worker_events_max_payload = { typ = "number" },
 
   upstream_keepalive_pool_size = { typ = "number" },

kong/templates/nginx.lua

@@ -31,8 +31,12 @@ wasm {
 > end
 
 > for _, el in ipairs(nginx_wasm_main_directives) do
+> if el.name == "shm_kv" then
+  shm_kv * $(el.value);
+> else
   $(el.name) $(el.value);
 > end
+> end
 
 > if #nginx_wasm_wasmtime_directives > 0 then
   wasmtime {

spec/01-unit/04-prefix_handler_spec.lua

@@ -911,10 +911,18 @@ describe("NGINX conf compiler", function()
       it("injects a shm_kv", function()
         assert.matches("wasm {.+shm_kv counters 10m;.+}", ngx_cfg({ wasm = true, nginx_wasm_shm_kv_counters="10m" }, debug))
       end)
+      it("injects a general shm_kv", function()
+        assert.matches("wasm {.+shm_kv %* 10m;.+}", ngx_cfg({ wasm = true, nginx_wasm_shm_kv="10m" }, debug))
+      end)
       it("injects multiple shm_kvs", function()
         assert.matches(
-          "wasm {.+shm_kv cache 10m.+shm_kv counters 10m;.+}",
-          ngx_cfg({ wasm = true, nginx_wasm_shm_kv_cache="10m", nginx_wasm_shm_kv_counters="10m"}, debug)
+          "wasm {.+shm_kv cache 10m.+shm_kv counters 10m;.+shm_kv %* 5m;.+}",
+          ngx_cfg({
+            wasm = true,
+            nginx_wasm_shm_kv_cache="10m",
+            nginx_wasm_shm_kv_counters="10m",
+            nginx_wasm_shm_kv="5m",
+          }, debug)
         )
       end)
       it("injects default configurations if wasm=on", function()

spec/fixtures/custom_nginx.template

@@ -41,8 +41,12 @@ wasm {
 > end
 
 > for _, el in ipairs(nginx_wasm_main_directives) do
+> if el.name == "shm_kv" then
+  shm_kv * $(el.value);
+> else
   $(el.name) $(el.value);
 > end
+> end
 
 > if #nginx_wasm_wasmtime_directives > 0 then
   wasmtime {