admin: lazy-init host stats and run with/without host stats for Json-…

…histograms (envoyproxy#32197)

Commit Message: Works around n^2 issue when destructing hundreds of thousands of mocks in the benchmark context. It does thi s by:

only initializing the hosts when per-host stats are enabled in the cluster config
adding a 'disabled' and 'enabled' variant to the histogram-json test so that it's easy to filter using --benchmark_filter=disabled to avoid initializing the hosts.
See also: envoyproxy#32198 -- this doesn't fix that bug but we could in theory revert this PR once that bug is fixed.
Additional Description:
Risk Level: low
Testing: just the one test
Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: n/a

Signed-off-by: Joshua Marantz <[email protected]>

test/server/admin/stats_handler_speed_test.cc

@@ -149,6 +149,11 @@ class StatsHandlerTest : public Stats::ThreadLocalRealThreadsMixin {
       }
     }
     store_->mergeHistograms([]() {});
+  }
+
+  void initClusterInfo() {
+    ENVOY_LOG_MISC(error, "Initializing cluster info; slow to construct and destruct...");
+    endpoint_stats_initialized_ = true;
 
     cm_.store_.fixed_tags_ = Stats::TagVector{{"fixed-tag", "fixed-value"}};
     for (uint32_t i = 0; i < NumClusters; i++) {
@@ -169,7 +174,12 @@ class StatsHandlerTest : public Stats::ThreadLocalRealThreadsMixin {
     }
   }
 
-  void setPerEndpointStats(bool enabled) { cm_.per_endpoint_enabled_ = enabled; }
+  void setPerEndpointStats(bool enabled) {
+    if (enabled && !endpoint_stats_initialized_) {
+      initClusterInfo();
+    }
+    cm_.per_endpoint_enabled_ = enabled;
+  }
 
   /**
    * Issues an admin request against the stats saved in store_.
@@ -196,6 +206,7 @@ class StatsHandlerTest : public Stats::ThreadLocalRealThreadsMixin {
   std::vector<Stats::ScopeSharedPtr> scopes_;
   Envoy::Stats::CustomStatNamespacesImpl custom_namespaces_;
   FastMockClusterManager cm_;
+  bool endpoint_stats_initialized_{false};
 };
 
 } // namespace Server
@@ -408,8 +419,8 @@ BENCHMARK_CAPTURE(BM_FilteredCountersPrometheus, per_endpoint_stats_enabled, tru
     ->Unit(benchmark::kMillisecond);
 
 // NOLINTNEXTLINE(readability-identifier-naming)
-static void BM_HistogramsJson(benchmark::State& state) {
-  Envoy::Server::StatsHandlerTest& test_context = testContext(false);
+static void BM_HistogramsJson(benchmark::State& state, bool per_endpoint_stats) {
+  Envoy::Server::StatsHandlerTest& test_context = testContext(per_endpoint_stats);
   Envoy::Server::StatsParams params;
   Envoy::Buffer::OwnedImpl response;
   params.parse("?format=json&type=Histograms&histogram_buckets=detailed", response);
@@ -424,4 +435,7 @@ static void BM_HistogramsJson(benchmark::State& state) {
   auto label = absl::StrCat("output per iteration: ", count);
   state.SetLabel(label);
 }
-BENCHMARK(BM_HistogramsJson)->Unit(benchmark::kMillisecond);
+BENCHMARK_CAPTURE(BM_HistogramsJson, per_endpoint_stats_disabled, false)
+    ->Unit(benchmark::kMillisecond);
+BENCHMARK_CAPTURE(BM_HistogramsJson, per_endpoint_stats_enabled, true)
+    ->Unit(benchmark::kMillisecond);