lua: add stats (#22623)

Currently stats are not available in lua filter, which makes it hard to
track/alert for the script errors. This change adds error stat.

Signed-off-by: Suresh Kumar <sureshkumar.pp@gmail.com>
Signed-off-by: Suresh Kumar <suresh.ponnusamy@freshworks.com>

api/envoy/extensions/filters/http/lua/v3/lua.proto

@@ -58,6 +58,26 @@ message Lua {
   // The default Lua code that Envoy will execute. If no per route config is provided
   // for the request, this Lua code will be applied.
   config.core.v3.DataSource default_source_code = 3;
+
+  // Optional additional prefix to use when emitting statistics. By default
+  // metrics are emitted in *.lua.* namespace. If multiple lua filters are
+  // configured in a filter chain, the stats from each filter instance can
+  // be emitted using custom stat prefix to distinguish emitted
+  // statistics. For example:
+  //
+  // .. code-block:: yaml
+  //
+  //   http_filters:
+  //     - name: envoy.filters.http.lua
+  //       typed_config:
+  //         "@type": type.googleapis.com/envoy.extensions.filters.http.lua.v3.Lua
+  //         stat_prefix: foo_script # This emits lua.foo_script.errors etc.
+  //     - name: envoy.filters.http.lua
+  //       typed_config:
+  //         "@type": type.googleapis.com/envoy.extensions.filters.http.lua.v3.Lua
+  //         stat_prefix: bar_script # This emits lua.bar_script.errors etc.
+  //
+  string stat_prefix = 4;
 }
 
 message LuaPerRoute {

changelogs/current.yaml

@@ -104,5 +104,8 @@ new_features:
 - area: access_log
   change: |
     added support for number values in substitution format string in json_format.
+- area: lua
+  change: |
+    added stats for lua filter, please see :ref:`lua filter stats <config_http_filters_lua_stats>`.
 
 deprecated:

docs/root/configuration/http/http_filters/lua_filter.rst

@@ -155,6 +155,21 @@ Lua script as follows:
             response_handle:logInfo("Goodbye.")
           end
 
+Statistics
+----------
+.. _config_http_filters_lua_stats:
+
+The lua filter outputs statistics in the *.lua.* namespace by default. When
+there are multiple lua filters configured in a filter chain, stats from
+individual filter instance/script can be tracked by providing a per filter
+:ref:`stat prefix
+<envoy_v3_api_field_extensions.filters.http.lua.v3.Lua.stat_prefix>`.
+
+.. csv-table::
+  :header: Name, Type, Description
+  :widths: 1, 1, 2
+
+  error, Counter, Total script execution errors.
 
 Script examples
 ---------------

source/extensions/filters/http/lua/config.cc

@@ -12,10 +12,11 @@ namespace HttpFilters {
 namespace Lua {
 
 Http::FilterFactoryCb LuaFilterConfig::createFilterFactoryFromProtoTyped(
-    const envoy::extensions::filters::http::lua::v3::Lua& proto_config, const std::string&,
-    Server::Configuration::FactoryContext& context) {
-  FilterConfigConstSharedPtr filter_config(new FilterConfig{
-      proto_config, context.threadLocal(), context.clusterManager(), context.api()});
+    const envoy::extensions::filters::http::lua::v3::Lua& proto_config,
+    const std::string& stat_prefix, Server::Configuration::FactoryContext& context) {
+  FilterConfigConstSharedPtr filter_config(new FilterConfig{proto_config, context.threadLocal(),
+                                                            context.clusterManager(), context.api(),
+                                                            context.scope(), stat_prefix});
   auto& time_source = context.mainThreadDispatcher().timeSource();
   return [filter_config, &time_source](Http::FilterChainFactoryCallbacks& callbacks) -> void {
     callbacks.addStreamFilter(std::make_shared<Filter>(filter_config, time_source));

source/extensions/filters/http/lua/config.h

@@ -21,8 +21,8 @@ class LuaFilterConfig
 
 private:
   Http::FilterFactoryCb createFilterFactoryFromProtoTyped(
-      const envoy::extensions::filters::http::lua::v3::Lua& proto_config, const std::string&,
-      Server::Configuration::FactoryContext& context) override;
+      const envoy::extensions::filters::http::lua::v3::Lua& proto_config,
+      const std::string& stats_prefix, Server::Configuration::FactoryContext& context) override;
 
   Router::RouteSpecificFilterConfigConstSharedPtr createRouteSpecificFilterConfigTyped(
       const envoy::extensions::filters::http::lua::v3::LuaPerRoute& proto_config,

source/extensions/filters/http/lua/lua_filter.cc

@@ -688,8 +688,10 @@ StreamHandleWrapper::getTimestampResolution(absl::string_view unit_parameter) {
 
 FilterConfig::FilterConfig(const envoy::extensions::filters::http::lua::v3::Lua& proto_config,
                            ThreadLocal::SlotAllocator& tls,
-                           Upstream::ClusterManager& cluster_manager, Api::Api& api)
-    : cluster_manager_(cluster_manager) {
+                           Upstream::ClusterManager& cluster_manager, Api::Api& api,
+                           Stats::Scope& scope, const std::string& stats_prefix)
+    : cluster_manager_(cluster_manager),
+      stats_(generateStats(stats_prefix, proto_config.stat_prefix(), scope)) {
   if (proto_config.has_default_source_code()) {
     if (!proto_config.inline_code().empty()) {
       throw EnvoyException("Error: Only one of `inline_code` or `default_source_code` can be set "
@@ -793,6 +795,7 @@ Http::FilterTrailersStatus Filter::doTrailers(StreamHandleRef& handle, Http::Hea
 }
 
 void Filter::scriptError(const Filters::Common::Lua::LuaException& e) {
+  stats_.errors_.inc();
   scriptLog(spdlog::level::err, e.what());
   request_stream_wrapper_.reset();
   response_stream_wrapper_.reset();

source/extensions/filters/http/lua/lua_filter.h

@@ -2,6 +2,7 @@
 
 #include "envoy/extensions/filters/http/lua/v3/lua.pb.h"
 #include "envoy/http/filter.h"
+#include "envoy/stats/stats_macros.h"
 #include "envoy/upstream/cluster_manager.h"
 
 #include "source/common/crypto/utility.h"
@@ -15,6 +16,18 @@ namespace Extensions {
 namespace HttpFilters {
 namespace Lua {
 
+/**
+ * All lua stats. @see stats_macros.h
+ */
+#define ALL_LUA_FILTER_STATS(COUNTER) COUNTER(errors)
+
+/**
+ * Struct definition for all Lua stats. @see stats_macros.h
+ */
+struct LuaFilterStats {
+  ALL_LUA_FILTER_STATS(GENERATE_COUNTER_STRUCT)
+};
+
 class PerLuaCodeSetup : Logger::Loggable<Logger::Id::lua> {
 public:
   PerLuaCodeSetup(const std::string& lua_code, ThreadLocal::SlotAllocator& tls);
@@ -357,7 +370,7 @@ class FilterConfig : Logger::Loggable<Logger::Id::lua> {
 public:
   FilterConfig(const envoy::extensions::filters::http::lua::v3::Lua& proto_config,
                ThreadLocal::SlotAllocator& tls, Upstream::ClusterManager& cluster_manager,
-               Api::Api& api);
+               Api::Api& api, Stats::Scope& scope, const std::string& stat_prefix);
 
   PerLuaCodeSetup* perLuaCodeSetup(absl::optional<absl::string_view> name = absl::nullopt) const {
     if (!name.has_value()) {
@@ -371,11 +384,20 @@ class FilterConfig : Logger::Loggable<Logger::Id::lua> {
     return nullptr;
   }
 
+  const LuaFilterStats& stats() const { return stats_; }
+
   Upstream::ClusterManager& cluster_manager_;
 
 private:
+  LuaFilterStats generateStats(const std::string& prefix, const std::string& filter_stats_prefix,
+                               Stats::Scope& scope) {
+    const std::string final_prefix = absl::StrCat(prefix, "lua.", filter_stats_prefix);
+    return {ALL_LUA_FILTER_STATS(POOL_COUNTER_PREFIX(scope, final_prefix))};
+  }
+
   PerLuaCodeSetupPtr default_lua_code_setup_;
   absl::flat_hash_map<std::string, PerLuaCodeSetupPtr> per_lua_code_setups_map_;
+  LuaFilterStats stats_;
 };
 
 using FilterConfigConstSharedPtr = std::shared_ptr<FilterConfig>;
@@ -448,7 +470,7 @@ PerLuaCodeSetup* getPerLuaCodeSetup(const FilterConfig* filter_config,
 class Filter : public Http::StreamFilter, Logger::Loggable<Logger::Id::lua> {
 public:
   Filter(FilterConfigConstSharedPtr config, TimeSource& time_source)
-      : config_(config), time_source_(time_source) {}
+      : config_(config), time_source_(time_source), stats_(config->stats()) {}
 
   Upstream::ClusterManager& clusterManager() { return config_->cluster_manager_; }
   void scriptError(const Filters::Common::Lua::LuaException& e);
@@ -561,6 +583,7 @@ class Filter : public Http::StreamFilter, Logger::Loggable<Logger::Id::lua> {
   StreamHandleRef response_stream_wrapper_;
   bool destroyed_{};
   TimeSource& time_source_;
+  LuaFilterStats stats_;
 
   // These coroutines used to be owned by the stream handles. After investigating #3570, it
   // became clear that there is a circular memory reference when a coroutine yields. Basically,