fix(wasm): add a startup check for missing filters

This adds a check during `init` that will prevent Kong from starting if
any filter chain entities are found in the database using a filter that
is not installed. Example:

> Error: ./kong/cmd/start.lua:99: nginx: [error] init_by_lua error: /path/to/kong/init.lua:750: [wasm]: found one or more filter chain entities with filters that are not enabled/installed:
> filter chain: 9e0b56d6-0e8c-469f-bf15-142debdd5d05, filter: #1 (response_transformer)
> filter chain: 9e0b56d6-0e8c-469f-bf15-142debdd5d05, filter: #3 (response_transformer)

Previously, this condition would not be caught until the Wasm state is
built during `init_worker`. This change brings Wasm more in line with the
behavior of the plugins iterator.

changelog/unreleased/kong/fix-wasm-check-missing-filters.yml

@@ -0,0 +1,5 @@
+message: |
+    **proxy-wasm:** Added a check that prevents Kong from starting when the
+    database contains invalid Wasm filters.
+type: bugfix
+scope: Core

kong/init.lua

@@ -745,6 +745,11 @@ function Kong.init()
     if not is_control_plane(config) then
       assert(runloop.build_router("init"))
 
+      ok, err = wasm.check_enabled_filters()
+      if not ok then
+        error("[wasm]: " .. err)
+      end
+
       ok, err = runloop.set_init_versions_in_cache()
       if not ok then
         error("error setting initial versions for router and plugins iterator in cache: " ..

kong/runloop/wasm.lua

@@ -1000,4 +1000,36 @@ function _M.status()
   return true
 end
 
+function _M.check_enabled_filters()
+  if not ENABLED then
+    return true
+  end
+
+  local enabled_filters = _M.filters_by_name
+
+  local errs
+  for chain, err in kong.db.filter_chains:each() do
+    if err then
+      return nil, err
+    end
+
+    for i, filter in ipairs(chain.filters) do
+      if not enabled_filters[filter.name] then
+        errs = errs or {}
+
+        insert(errs, fmt("filter chain: %s, filter: #%s (%s)",
+                         chain.id, i, filter.name))
+      end
+    end
+  end
+
+  if errs then
+    return nil, "found one or more filter chain entities with filters that are "
+             .. "not enabled/installed:\n" .. table.concat(errs, "\n")
+  end
+
+
+  return true
+end
+
 return _M

spec/02-integration/20-wasm/11-missing-filters_spec.lua

@@ -0,0 +1,87 @@
+local helpers = require "spec.helpers"
+
+local FILTER_PATH = assert(helpers.test_conf.wasm_filters_path)
+
+-- no cassandra support
+for _, strategy in helpers.each_strategy({ "postgres" }) do
+
+describe("missing filters in the config [#" .. strategy .. "]", function()
+  local bp
+  local service, route
+
+  lazy_setup(function()
+    require("kong.runloop.wasm").enable({
+      { name = "tests",
+        path = FILTER_PATH .. "/tests.wasm",
+      },
+      { name = "response_transformer",
+        path = FILTER_PATH .. "/response_transformer.wasm",
+      },
+    })
+
+    bp = helpers.get_db_utils(strategy, {
+      "routes",
+      "services",
+      "filter_chains",
+    })
+
+    service = assert(bp.services:insert {
+      name = "wasm-test",
+    })
+
+    route = assert(bp.routes:insert {
+      service = service,
+      paths = { "/" },
+    })
+
+    assert(bp.filter_chains:insert {
+      name = "test",
+      route = route,
+      filters = {
+        {
+          name = "response_transformer",
+          config = require("cjson").encode {
+            append = {
+              headers = {
+                "x-wasm-test:my-value",
+              },
+            },
+          }
+        },
+        {
+          name = "tests",
+          config = nil,
+        },
+        {
+          name = "response_transformer",
+          config = require("cjson").encode {
+            append = {
+              headers = {
+                "x-wasm-test:my-value",
+              },
+            },
+          }
+        }
+      }
+    })
+  end)
+
+  lazy_teardown(function()
+    helpers.clean_prefix()
+  end)
+
+  it("causes Kong to fail to start", function()
+    local ok, err = helpers.start_kong({
+      database = strategy,
+      nginx_conf = "spec/fixtures/custom_nginx.template",
+      wasm_filters = "tests",
+      wasm = true,
+    })
+
+    assert.falsy(ok, "expected `kong start` to fail")
+    assert.string(err)
+    assert.matches("response_transformer", err)
+  end)
+end)
+
+end -- each strategy