Convert retry throttle code to C++ and add tests.

1 files changed, 100 insertions, 122 deletions

diff --git a/src/core/ext/filters/client_channel/retry_throttle.cc b/src/core/ext/filters/client_channel/retry_throttle.cc
index 45de6667c8..bdeb7e4cac 100644
--- a/src/core/ext/filters/client_channel/retry_throttle.cc
+++ b/src/core/ext/filters/client_channel/retry_throttle.cc
@@ -30,184 +30,162 @@
 
 #include "src/core/lib/avl/avl.h"
 
+namespace grpc_core {
+namespace internal {
+
 //
-// server_retry_throttle_data
+// ServerRetryThrottleData
 //
 
-struct grpc_server_retry_throttle_data {
-  gpr_refcount refs;
-  int max_milli_tokens;
-  int milli_token_ratio;
-  gpr_atm milli_tokens;
-  // A pointer to the replacement for this grpc_server_retry_throttle_data
-  // entry.  If non-nullptr, then this entry is stale and must not be used.
-  // We hold a reference to the replacement.
-  gpr_atm replacement;
-};
-
-static void get_replacement_throttle_data_if_needed(
-    grpc_server_retry_throttle_data** throttle_data) {
+ServerRetryThrottleData::ServerRetryThrottleData(
+    intptr_t max_milli_tokens, intptr_t milli_token_ratio,
+    ServerRetryThrottleData* old_throttle_data)
+    : max_milli_tokens_(max_milli_tokens),
+      milli_token_ratio_(milli_token_ratio) {
+  intptr_t initial_milli_tokens = max_milli_tokens;
+  // If there was a pre-existing entry for this server name, initialize
+  // the token count by scaling proportionately to the old data.  This
+  // ensures that if we're already throttling retries on the old scale,
+  // we will start out doing the same thing on the new one.
+  if (old_throttle_data != nullptr) {
+    double token_fraction =
+        static_cast<intptr_t>(
+            gpr_atm_acq_load(&old_throttle_data->milli_tokens_)) /
+        static_cast<double>(old_throttle_data->max_milli_tokens_);
+    initial_milli_tokens =
+        static_cast<intptr_t>(token_fraction * max_milli_tokens);
+  }
+  gpr_atm_rel_store(&milli_tokens_, static_cast<gpr_atm>(initial_milli_tokens));
+  // If there was a pre-existing entry, mark it as stale and give it a
+  // pointer to the new entry, which is its replacement.
+  if (old_throttle_data != nullptr) {
+    Ref().release();  // Ref held by pre-existing entry.
+    gpr_atm_rel_store(&old_throttle_data->replacement_,
+                      reinterpret_cast<gpr_atm>(this));
+  }
+}
+
+ServerRetryThrottleData::~ServerRetryThrottleData() {
+  ServerRetryThrottleData* replacement =
+      reinterpret_cast<ServerRetryThrottleData*>(
+          gpr_atm_acq_load(&replacement_));
+  if (replacement != nullptr) {
+    replacement->Unref();
+  }
+}
+
+void ServerRetryThrottleData::GetReplacementThrottleDataIfNeeded(
+    ServerRetryThrottleData** throttle_data) {
   while (true) {
-    grpc_server_retry_throttle_data* new_throttle_data =
-        (grpc_server_retry_throttle_data*)gpr_atm_acq_load(
-            &(*throttle_data)->replacement);
+    ServerRetryThrottleData* new_throttle_data =
+        reinterpret_cast<ServerRetryThrottleData*>(
+            gpr_atm_acq_load(&(*throttle_data)->replacement_));
     if (new_throttle_data == nullptr) return;
     *throttle_data = new_throttle_data;
   }
 }
 
-bool grpc_server_retry_throttle_data_record_failure(
-    grpc_server_retry_throttle_data* throttle_data) {
-  if (throttle_data == nullptr) return true;
+bool ServerRetryThrottleData::RecordFailure() {
   // First, check if we are stale and need to be replaced.
-  get_replacement_throttle_data_if_needed(&throttle_data);
+  ServerRetryThrottleData* throttle_data = this;
+  GetReplacementThrottleDataIfNeeded(&throttle_data);
   // We decrement milli_tokens by 1000 (1 token) for each failure.
-  const int new_value = static_cast<int>(gpr_atm_no_barrier_clamped_add(
-      &throttle_data->milli_tokens, static_cast<gpr_atm>(-1000),
-      static_cast<gpr_atm>(0),
-      static_cast<gpr_atm>(throttle_data->max_milli_tokens)));
+  const intptr_t new_value =
+      static_cast<intptr_t>(gpr_atm_no_barrier_clamped_add(
+          &throttle_data->milli_tokens_, static_cast<gpr_atm>(-1000),
+          static_cast<gpr_atm>(0),
+          static_cast<gpr_atm>(throttle_data->max_milli_tokens_)));
   // Retries are allowed as long as the new value is above the threshold
   // (max_milli_tokens / 2).
-  return new_value > throttle_data->max_milli_tokens / 2;
+  return new_value > throttle_data->max_milli_tokens_ / 2;
 }
 
-void grpc_server_retry_throttle_data_record_success(
-    grpc_server_retry_throttle_data* throttle_data) {
-  if (throttle_data == nullptr) return;
+void ServerRetryThrottleData::RecordSuccess() {
   // First, check if we are stale and need to be replaced.
-  get_replacement_throttle_data_if_needed(&throttle_data);
+  ServerRetryThrottleData* throttle_data = this;
+  GetReplacementThrottleDataIfNeeded(&throttle_data);
   // We increment milli_tokens by milli_token_ratio for each success.
   gpr_atm_no_barrier_clamped_add(
-      &throttle_data->milli_tokens,
-      static_cast<gpr_atm>(throttle_data->milli_token_ratio),
+      &throttle_data->milli_tokens_,
+      static_cast<gpr_atm>(throttle_data->milli_token_ratio_),
       static_cast<gpr_atm>(0),
-      static_cast<gpr_atm>(throttle_data->max_milli_tokens));
-}
-
-grpc_server_retry_throttle_data* grpc_server_retry_throttle_data_ref(
-    grpc_server_retry_throttle_data* throttle_data) {
-  gpr_ref(&throttle_data->refs);
-  return throttle_data;
-}
-
-void grpc_server_retry_throttle_data_unref(
-    grpc_server_retry_throttle_data* throttle_data) {
-  if (gpr_unref(&throttle_data->refs)) {
-    grpc_server_retry_throttle_data* replacement =
-        (grpc_server_retry_throttle_data*)gpr_atm_acq_load(
-            &throttle_data->replacement);
-    if (replacement != nullptr) {
-      grpc_server_retry_throttle_data_unref(replacement);
-    }
-    gpr_free(throttle_data);
-  }
-}
-
-static grpc_server_retry_throttle_data* grpc_server_retry_throttle_data_create(
-    int max_milli_tokens, int milli_token_ratio,
-    grpc_server_retry_throttle_data* old_throttle_data) {
-  grpc_server_retry_throttle_data* throttle_data =
-      static_cast<grpc_server_retry_throttle_data*>(
-          gpr_malloc(sizeof(*throttle_data)));
-  memset(throttle_data, 0, sizeof(*throttle_data));
-  gpr_ref_init(&throttle_data->refs, 1);
-  throttle_data->max_milli_tokens = max_milli_tokens;
-  throttle_data->milli_token_ratio = milli_token_ratio;
-  int initial_milli_tokens = max_milli_tokens;
-  // If there was a pre-existing entry for this server name, initialize
-  // the token count by scaling proportionately to the old data.  This
-  // ensures that if we're already throttling retries on the old scale,
-  // we will start out doing the same thing on the new one.
-  if (old_throttle_data != nullptr) {
-    double token_fraction =
-        static_cast<int>(gpr_atm_acq_load(&old_throttle_data->milli_tokens)) /
-        static_cast<double>(old_throttle_data->max_milli_tokens);
-    initial_milli_tokens = static_cast<int>(token_fraction * max_milli_tokens);
-  }
-  gpr_atm_rel_store(&throttle_data->milli_tokens,
-                    (gpr_atm)initial_milli_tokens);
-  // If there was a pre-existing entry, mark it as stale and give it a
-  // pointer to the new entry, which is its replacement.
-  if (old_throttle_data != nullptr) {
-    grpc_server_retry_throttle_data_ref(throttle_data);
-    gpr_atm_rel_store(&old_throttle_data->replacement, (gpr_atm)throttle_data);
-  }
-  return throttle_data;
+      static_cast<gpr_atm>(throttle_data->max_milli_tokens_));
 }
 
 //
 // avl vtable for string -> server_retry_throttle_data map
 //
 
-static void* copy_server_name(void* key, void* unused) {
+namespace {
+
+void* copy_server_name(void* key, void* unused) {
   return gpr_strdup(static_cast<const char*>(key));
 }
 
-static long compare_server_name(void* key1, void* key2, void* unused) {
+long compare_server_name(void* key1, void* key2, void* unused) {
   return strcmp(static_cast<const char*>(key1), static_cast<const char*>(key2));
 }
 
-static void destroy_server_retry_throttle_data(void* value, void* unused) {
-  grpc_server_retry_throttle_data* throttle_data =
-      static_cast<grpc_server_retry_throttle_data*>(value);
-  grpc_server_retry_throttle_data_unref(throttle_data);
+void destroy_server_retry_throttle_data(void* value, void* unused) {
+  ServerRetryThrottleData* throttle_data =
+      static_cast<ServerRetryThrottleData*>(value);
+  throttle_data->Unref();
 }
 
-static void* copy_server_retry_throttle_data(void* value, void* unused) {
-  grpc_server_retry_throttle_data* throttle_data =
-      static_cast<grpc_server_retry_throttle_data*>(value);
-  return grpc_server_retry_throttle_data_ref(throttle_data);
+void* copy_server_retry_throttle_data(void* value, void* unused) {
+  ServerRetryThrottleData* throttle_data =
+      static_cast<ServerRetryThrottleData*>(value);
+  return throttle_data->Ref().release();
 }
 
-static void destroy_server_name(void* key, void* unused) { gpr_free(key); }
+void destroy_server_name(void* key, void* unused) { gpr_free(key); }
 
-static const grpc_avl_vtable avl_vtable = {
+const grpc_avl_vtable avl_vtable = {
     destroy_server_name, copy_server_name, compare_server_name,
     destroy_server_retry_throttle_data, copy_server_retry_throttle_data};
 
+}  // namespace
+
 //
-// server_retry_throttle_map
+// ServerRetryThrottleMap
 //
 
 static gpr_mu g_mu;
 static grpc_avl g_avl;
 
-void grpc_retry_throttle_map_init() {
+void ServerRetryThrottleMap::Init() {
   gpr_mu_init(&g_mu);
   g_avl = grpc_avl_create(&avl_vtable);
 }
 
-void grpc_retry_throttle_map_shutdown() {
+void ServerRetryThrottleMap::Shutdown() {
   gpr_mu_destroy(&g_mu);
   grpc_avl_unref(g_avl, nullptr);
 }
 
-grpc_server_retry_throttle_data* grpc_retry_throttle_map_get_data_for_server(
-    const char* server_name, int max_milli_tokens, int milli_token_ratio) {
+RefCountedPtr<ServerRetryThrottleData> ServerRetryThrottleMap::GetDataForServer(
+    const char* server_name, intptr_t max_milli_tokens,
+    intptr_t milli_token_ratio) {
+  RefCountedPtr<ServerRetryThrottleData> result;
   gpr_mu_lock(&g_mu);
-  grpc_server_retry_throttle_data* throttle_data =
-      static_cast<grpc_server_retry_throttle_data*>(
+  ServerRetryThrottleData* throttle_data =
+      static_cast<ServerRetryThrottleData*>(
           grpc_avl_get(g_avl, const_cast<char*>(server_name), nullptr));
-  if (throttle_data == nullptr) {
-    // Entry not found.  Create a new one.
-    throttle_data = grpc_server_retry_throttle_data_create(
-        max_milli_tokens, milli_token_ratio, nullptr);
-    g_avl = grpc_avl_add(g_avl, const_cast<char*>(server_name), throttle_data,
-                         nullptr);
+  if (throttle_data == nullptr ||
+      throttle_data->max_milli_tokens() != max_milli_tokens ||
+      throttle_data->milli_token_ratio() != milli_token_ratio) {
+    // Entry not found, or found with old parameters.  Create a new one.
+    result = MakeRefCounted<ServerRetryThrottleData>(
+        max_milli_tokens, milli_token_ratio, throttle_data);
+    g_avl = grpc_avl_add(g_avl, gpr_strdup(server_name),
+                         result->Ref().release(), nullptr);
   } else {
-    if (throttle_data->max_milli_tokens != max_milli_tokens ||
-        throttle_data->milli_token_ratio != milli_token_ratio) {
-      // Entry found but with old parameters.  Create a new one based on
-      // the original one.
-      throttle_data = grpc_server_retry_throttle_data_create(
-          max_milli_tokens, milli_token_ratio, throttle_data);
-      g_avl = grpc_avl_add(g_avl, const_cast<char*>(server_name), throttle_data,
-                           nullptr);
-    } else {
-      // Entry found.  Increase refcount.
-      grpc_server_retry_throttle_data_ref(throttle_data);
-    }
+    // Entry found.  Return a new ref to it.
+    result = throttle_data->Ref();
   }
   gpr_mu_unlock(&g_mu);
-  return throttle_data;
+  return result;
 }
+
+}  // namespace internal
+}  // namespace grpc_core