C++-ize backoff

src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc

@@ -113,6 +113,7 @@
 #include "src/core/lib/slice/slice_hash_table.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
+#include "src/core/lib/support/alloc_new.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel.h"
@@ -397,7 +398,7 @@ typedef struct glb_lb_policy {
   grpc_slice lb_call_status_details;
 
   /** LB call retry backoff state */
-  grpc_backoff lb_call_backoff_state;
+  grpc_core::Backoff* lb_call_backoff;
 
   /** LB call retry timer */
   grpc_timer lb_call_retry_timer;
@@ -986,6 +987,7 @@ static void glb_destroy(grpc_exec_ctx* exec_ctx, grpc_lb_policy* pol) {
   }
   grpc_fake_resolver_response_generator_unref(glb_policy->response_generator);
   grpc_subchannel_index_unref();
+  gpr_free(glb_policy->lb_call_backoff);
   gpr_free(glb_policy);
 }
 
@@ -1150,7 +1152,7 @@ static void start_picking_locked(grpc_exec_ctx* exec_ctx,
   }
 
   glb_policy->started_picking = true;
-  grpc_backoff_reset(&glb_policy->lb_call_backoff_state);
+  glb_policy->lb_call_backoff->Reset();
   query_for_backends_locked(exec_ctx, glb_policy);
 }
 
@@ -1291,8 +1293,7 @@ static void maybe_restart_lb_call(grpc_exec_ctx* exec_ctx,
   } else if (!glb_policy->shutting_down) {
     /* if we aren't shutting down, restart the LB client call after some time */
     grpc_millis next_try =
-        grpc_backoff_step(exec_ctx, &glb_policy->lb_call_backoff_state)
-            .next_attempt_start_time;
+        glb_policy->lb_call_backoff->Step(exec_ctx).next_attempt_start_time;
     if (grpc_lb_glb_trace.enabled()) {
       gpr_log(GPR_DEBUG, "[grpclb %p] Connection to LB server lost...",
               glb_policy);
@@ -1461,12 +1462,14 @@ static void lb_call_init_locked(grpc_exec_ctx* exec_ctx,
                     lb_on_response_received_locked, glb_policy,
                     grpc_combiner_scheduler(glb_policy->base.combiner));
 
-  grpc_backoff_init(&glb_policy->lb_call_backoff_state,
-                    GRPC_GRPCLB_INITIAL_CONNECT_BACKOFF_SECONDS * 1000,
-                    GRPC_GRPCLB_RECONNECT_BACKOFF_MULTIPLIER,
-                    GRPC_GRPCLB_RECONNECT_JITTER,
-                    GRPC_GRPCLB_MIN_CONNECT_TIMEOUT_SECONDS * 1000,
-                    GRPC_GRPCLB_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  grpc_core::Backoff::Options backoff_options;
+  backoff_options
+      .set_initial_backoff(GRPC_GRPCLB_INITIAL_CONNECT_BACKOFF_SECONDS * 1000)
+      .set_multiplier(GRPC_GRPCLB_RECONNECT_BACKOFF_MULTIPLIER)
+      .set_jitter(GRPC_GRPCLB_RECONNECT_JITTER)
+      .set_min_connect_timeout(GRPC_GRPCLB_MIN_CONNECT_TIMEOUT_SECONDS * 1000)
+      .set_max_backoff(GRPC_GRPCLB_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  glb_policy->lb_call_backoff = GPR_NEW(grpc_core::Backoff(backoff_options));
 
   glb_policy->seen_initial_response = false;
   glb_policy->last_client_load_report_counters_were_zero = false;
@@ -1573,7 +1576,7 @@ static void lb_on_response_received_locked(grpc_exec_ctx* exec_ctx, void* arg,
   memset(ops, 0, sizeof(ops));
   grpc_op* op = ops;
   if (glb_policy->lb_response_payload != nullptr) {
-    grpc_backoff_reset(&glb_policy->lb_call_backoff_state);
+    glb_policy->lb_call_backoff->Reset();
     /* Received data from the LB server. Look inside
      * glb_policy->lb_response_payload, for a serverlist. */
     grpc_byte_buffer_reader bbr;

src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc

@@ -39,6 +39,7 @@
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/json/json.h"
+#include "src/core/lib/support/alloc_new.h"
 #include "src/core/lib/support/env.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/transport/service_config.h"
@@ -89,7 +90,7 @@ typedef struct {
   bool have_retry_timer;
   grpc_timer retry_timer;
   /** retry backoff state */
-  grpc_backoff backoff_state;
+  grpc_core::Backoff* backoff;
 
   /** currently resolving addresses */
   grpc_lb_addresses* lb_addresses;
@@ -137,7 +138,7 @@ static void dns_ares_channel_saw_error_locked(grpc_exec_ctx* exec_ctx,
                                               grpc_resolver* resolver) {
   ares_dns_resolver* r = (ares_dns_resolver*)resolver;
   if (!r->resolving) {
-    grpc_backoff_reset(&r->backoff_state);
+    r->backoff->Reset();
     dns_ares_start_resolving_locked(exec_ctx, r);
   }
 }
@@ -272,8 +273,7 @@ static void dns_ares_on_resolved_locked(grpc_exec_ctx* exec_ctx, void* arg,
   } else {
     const char* msg = grpc_error_string(error);
     gpr_log(GPR_DEBUG, "dns resolution failed: %s", msg);
-    grpc_millis next_try =
-        grpc_backoff_step(exec_ctx, &r->backoff_state).next_attempt_start_time;
+    grpc_millis next_try = r->backoff->Step(exec_ctx).next_attempt_start_time;
     grpc_millis timeout = next_try - grpc_exec_ctx_now(exec_ctx);
     gpr_log(GPR_INFO, "dns resolution failed (will retry): %s",
             grpc_error_string(error));
@@ -307,7 +307,7 @@ static void dns_ares_next_locked(grpc_exec_ctx* exec_ctx,
   r->next_completion = on_complete;
   r->target_result = target_result;
   if (r->resolved_version == 0 && !r->resolving) {
-    grpc_backoff_reset(&r->backoff_state);
+    r->backoff->Reset();
     dns_ares_start_resolving_locked(exec_ctx, r);
   } else {
     dns_ares_maybe_finish_next_locked(exec_ctx, r);
@@ -353,6 +353,7 @@ static void dns_ares_destroy(grpc_exec_ctx* exec_ctx, grpc_resolver* gr) {
   gpr_free(r->name_to_resolve);
   gpr_free(r->default_port);
   grpc_channel_args_destroy(exec_ctx, r->channel_args);
+  gpr_free(r->backoff);
   gpr_free(r);
 }
 
@@ -381,11 +382,14 @@ static grpc_resolver* dns_ares_create(grpc_exec_ctx* exec_ctx,
     grpc_pollset_set_add_pollset_set(exec_ctx, r->interested_parties,
                                      args->pollset_set);
   }
-  grpc_backoff_init(
-      &r->backoff_state, GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS * 1000,
-      GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER, GRPC_DNS_RECONNECT_JITTER,
-      GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS * 1000,
-      GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  grpc_core::Backoff::Options backoff_options;
+  backoff_options
+      .set_initial_backoff(GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS * 1000)
+      .set_multiplier(GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER)
+      .set_jitter(GRPC_DNS_RECONNECT_JITTER)
+      .set_min_connect_timeout(GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS * 1000)
+      .set_max_backoff(GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  r->backoff = GPR_NEW(grpc_core::Backoff(backoff_options));
   GRPC_CLOSURE_INIT(&r->dns_ares_on_retry_timer_locked,
                     dns_ares_on_retry_timer_locked, r,
                     grpc_combiner_scheduler(r->base.combiner));

src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.cc

@@ -32,6 +32,7 @@
 #include "src/core/lib/iomgr/combiner.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/timer.h"
+#include "src/core/lib/support/alloc_new.h"
 #include "src/core/lib/support/env.h"
 #include "src/core/lib/support/string.h"
 
@@ -70,7 +71,7 @@ typedef struct {
   grpc_timer retry_timer;
   grpc_closure on_retry;
   /** retry backoff state */
-  grpc_backoff backoff_state;
+  grpc_core::Backoff* backoff;
 
   /** currently resolving addresses */
   grpc_resolved_addresses* addresses;
@@ -113,7 +114,7 @@ static void dns_channel_saw_error_locked(grpc_exec_ctx* exec_ctx,
                                          grpc_resolver* resolver) {
   dns_resolver* r = (dns_resolver*)resolver;
   if (!r->resolving) {
-    grpc_backoff_reset(&r->backoff_state);
+    r->backoff->Reset();
     dns_start_resolving_locked(exec_ctx, r);
   }
 }
@@ -126,7 +127,7 @@ static void dns_next_locked(grpc_exec_ctx* exec_ctx, grpc_resolver* resolver,
   r->next_completion = on_complete;
   r->target_result = target_result;
   if (r->resolved_version == 0 && !r->resolving) {
-    grpc_backoff_reset(&r->backoff_state);
+    r->backoff->Reset();
     dns_start_resolving_locked(exec_ctx, r);
   } else {
     dns_maybe_finish_next_locked(exec_ctx, r);
@@ -170,8 +171,7 @@ static void dns_on_resolved_locked(grpc_exec_ctx* exec_ctx, void* arg,
     grpc_resolved_addresses_destroy(r->addresses);
     grpc_lb_addresses_destroy(exec_ctx, addresses);
   } else {
-    grpc_millis next_try =
-        grpc_backoff_step(exec_ctx, &r->backoff_state).next_attempt_start_time;
+    grpc_millis next_try = r->backoff->Step(exec_ctx).next_attempt_start_time;
     grpc_millis timeout = next_try - grpc_exec_ctx_now(exec_ctx);
     gpr_log(GPR_INFO, "dns resolution failed (will retry): %s",
             grpc_error_string(error));
@@ -233,6 +233,7 @@ static void dns_destroy(grpc_exec_ctx* exec_ctx, grpc_resolver* gr) {
   gpr_free(r->name_to_resolve);
   gpr_free(r->default_port);
   grpc_channel_args_destroy(exec_ctx, r->channel_args);
+  gpr_free(r->backoff);
   gpr_free(r);
 }
 
@@ -257,11 +258,14 @@ static grpc_resolver* dns_create(grpc_exec_ctx* exec_ctx,
     grpc_pollset_set_add_pollset_set(exec_ctx, r->interested_parties,
                                      args->pollset_set);
   }
-  grpc_backoff_init(
-      &r->backoff_state, GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS * 1000,
-      GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER, GRPC_DNS_RECONNECT_JITTER,
-      GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS * 1000,
-      GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  grpc_core::Backoff::Options backoff_options;
+  backoff_options
+      .set_initial_backoff(GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS * 1000)
+      .set_multiplier(GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER)
+      .set_jitter(GRPC_DNS_RECONNECT_JITTER)
+      .set_min_connect_timeout(GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS * 1000)
+      .set_max_backoff(GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  r->backoff = GPR_NEW(grpc_core::Backoff(backoff_options));
   return &r->base;
 }
 

src/core/ext/filters/client_channel/subchannel.cc

@@ -39,6 +39,7 @@
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
+#include "src/core/lib/support/alloc_new.h"
 #include "src/core/lib/surface/channel.h"
 #include "src/core/lib/surface/channel_init.h"
 #include "src/core/lib/transport/connectivity_state.h"
@@ -72,6 +73,9 @@ typedef struct external_state_watcher {
 } external_state_watcher;
 
 struct grpc_subchannel {
+  grpc_subchannel(const grpc_core::Backoff::Options& backoff_options)
+      : backoff(backoff_options) {}
+
   grpc_connector* connector;
 
   /** refcount
@@ -118,8 +122,8 @@ struct grpc_subchannel {
   external_state_watcher root_external_state_watcher;
 
   /** backoff state */
-  grpc_backoff backoff_state;
-  grpc_backoff_result backoff_result;
+  grpc_core::Backoff backoff;
+  grpc_core::Backoff::Result backoff_result;
 
   /** do we have an active alarm? */
   bool have_alarm;
@@ -283,6 +287,52 @@ void grpc_subchannel_weak_unref(grpc_exec_ctx* exec_ctx,
   }
 }
 
+static grpc_core::Backoff::Options extract_backoff_options(
+    const grpc_channel_args* args) {
+  int initial_backoff_ms =
+      GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000;
+  int min_connect_timeout_ms =
+      GRPC_SUBCHANNEL_RECONNECT_MIN_BACKOFF_SECONDS * 1000;
+  int max_backoff_ms = GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000;
+  bool fixed_reconnect_backoff = false;
+  if (args != nullptr) {
+    for (size_t i = 0; i < args->num_args; i++) {
+      if (0 == strcmp(args->args[i].key,
+                      "grpc.testing.fixed_reconnect_backoff_ms")) {
+        fixed_reconnect_backoff = true;
+        initial_backoff_ms = min_connect_timeout_ms = max_backoff_ms =
+            grpc_channel_arg_get_integer(&args->args[i],
+                                         {initial_backoff_ms, 100, INT_MAX});
+      } else if (0 ==
+                 strcmp(args->args[i].key, GRPC_ARG_MIN_RECONNECT_BACKOFF_MS)) {
+        fixed_reconnect_backoff = false;
+        min_connect_timeout_ms = grpc_channel_arg_get_integer(
+            &args->args[i], {min_connect_timeout_ms, 100, INT_MAX});
+      } else if (0 ==
+                 strcmp(args->args[i].key, GRPC_ARG_MAX_RECONNECT_BACKOFF_MS)) {
+        fixed_reconnect_backoff = false;
+        max_backoff_ms = grpc_channel_arg_get_integer(
+            &args->args[i], {max_backoff_ms, 100, INT_MAX});
+      } else if (0 == strcmp(args->args[i].key,
+                             GRPC_ARG_INITIAL_RECONNECT_BACKOFF_MS)) {
+        fixed_reconnect_backoff = false;
+        initial_backoff_ms = grpc_channel_arg_get_integer(
+            &args->args[i], {initial_backoff_ms, 100, INT_MAX});
+      }
+    }
+  }
+  grpc_core::Backoff::Options backoff_options;
+  backoff_options.set_initial_backoff(initial_backoff_ms)
+      .set_multiplier(fixed_reconnect_backoff
+                          ? 1.0
+                          : GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER)
+      .set_jitter(fixed_reconnect_backoff ? 0.0
+                                          : GRPC_SUBCHANNEL_RECONNECT_JITTER)
+      .set_min_connect_timeout(min_connect_timeout_ms)
+      .set_max_backoff(max_backoff_ms);
+  return backoff_options;
+}
+
 grpc_subchannel* grpc_subchannel_create(grpc_exec_ctx* exec_ctx,
                                         grpc_connector* connector,
                                         const grpc_subchannel_args* args) {
@@ -294,7 +344,7 @@ grpc_subchannel* grpc_subchannel_create(grpc_exec_ctx* exec_ctx,
   }
 
   GRPC_STATS_INC_CLIENT_SUBCHANNELS_CREATED(exec_ctx);
-  c = (grpc_subchannel*)gpr_zalloc(sizeof(*c));
+  c = GPR_NEW(grpc_subchannel(extract_backoff_options(args->args)));
   c->key = key;
   gpr_atm_no_barrier_store(&c->ref_pair, 1 << INTERNAL_REF_BITS);
   c->connector = connector;
@@ -336,7 +386,8 @@ grpc_subchannel* grpc_subchannel_create(grpc_exec_ctx* exec_ctx,
                                "subchannel");
   int initial_backoff_ms =
       GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000;
-  int min_backoff_ms = GRPC_SUBCHANNEL_RECONNECT_MIN_BACKOFF_SECONDS * 1000;
+  int min_connect_timeout_ms =
+      GRPC_SUBCHANNEL_RECONNECT_MIN_BACKOFF_SECONDS * 1000;
   int max_backoff_ms = GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000;
   bool fixed_reconnect_backoff = false;
   if (c->args) {
@@ -344,14 +395,14 @@ grpc_subchannel* grpc_subchannel_create(grpc_exec_ctx* exec_ctx,
       if (0 == strcmp(c->args->args[i].key,
                       "grpc.testing.fixed_reconnect_backoff_ms")) {
         fixed_reconnect_backoff = true;
-        initial_backoff_ms = min_backoff_ms = max_backoff_ms =
+        initial_backoff_ms = min_connect_timeout_ms = max_backoff_ms =
             grpc_channel_arg_get_integer(&c->args->args[i],
                                          {initial_backoff_ms, 100, INT_MAX});
       } else if (0 == strcmp(c->args->args[i].key,
                              GRPC_ARG_MIN_RECONNECT_BACKOFF_MS)) {
         fixed_reconnect_backoff = false;
-        min_backoff_ms = grpc_channel_arg_get_integer(
-            &c->args->args[i], {min_backoff_ms, 100, INT_MAX});
+        min_connect_timeout_ms = grpc_channel_arg_get_integer(
+            &c->args->args[i], {min_connect_timeout_ms, 100, INT_MAX});
       } else if (0 == strcmp(c->args->args[i].key,
                              GRPC_ARG_MAX_RECONNECT_BACKOFF_MS)) {
         fixed_reconnect_backoff = false;
@@ -365,12 +416,15 @@ grpc_subchannel* grpc_subchannel_create(grpc_exec_ctx* exec_ctx,
       }
     }
   }
-  grpc_backoff_init(
-      &c->backoff_state, initial_backoff_ms,
-      fixed_reconnect_backoff ? 1.0
-                              : GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
-      fixed_reconnect_backoff ? 0.0 : GRPC_SUBCHANNEL_RECONNECT_JITTER,
-      min_backoff_ms, max_backoff_ms);
+  grpc_core::Backoff::Options backoff_options;
+  backoff_options.set_initial_backoff(initial_backoff_ms)
+      .set_multiplier(fixed_reconnect_backoff
+                          ? 1.0
+                          : GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER)
+      .set_jitter(fixed_reconnect_backoff ? 0.0
+                                          : GRPC_SUBCHANNEL_RECONNECT_JITTER)
+      .set_min_connect_timeout(min_connect_timeout_ms)
+      .set_max_backoff(max_backoff_ms);
   gpr_mu_init(&c->mu);
 
   return grpc_subchannel_index_register(exec_ctx, key, c);
@@ -429,7 +483,7 @@ static void on_alarm(grpc_exec_ctx* exec_ctx, void* arg, grpc_error* error) {
   }
   if (error == GRPC_ERROR_NONE) {
     gpr_log(GPR_INFO, "Failed to connect to channel, retrying");
-    c->backoff_result = grpc_backoff_step(exec_ctx, &c->backoff_state);
+    c->backoff_result = c->backoff.Step(exec_ctx);
     continue_connect_locked(exec_ctx, c);
     gpr_mu_unlock(&c->mu);
   } else {
@@ -466,7 +520,7 @@ static void maybe_start_connecting_locked(grpc_exec_ctx* exec_ctx,
 
   if (!c->backoff_begun) {
     c->backoff_begun = true;
-    c->backoff_result = grpc_backoff_begin(exec_ctx, &c->backoff_state);
+    c->backoff_result = c->backoff.Begin(exec_ctx);
     continue_connect_locked(exec_ctx, c);
   } else {
     GPR_ASSERT(!c->have_alarm);

src/core/lib/backoff/backoff.cc

@@ -18,63 +18,52 @@
 
 #include "src/core/lib/backoff/backoff.h"
 
+#include <algorithm>
+#include <cstdlib>
+
 #include <grpc/support/useful.h>
 
-void grpc_backoff_init(grpc_backoff* backoff, grpc_millis initial_backoff,
-                       double multiplier, double jitter,
-                       grpc_millis min_connect_timeout,
-                       grpc_millis max_backoff) {
-  backoff->initial_backoff = initial_backoff;
-  backoff->multiplier = multiplier;
-  backoff->jitter = jitter;
-  backoff->min_connect_timeout = min_connect_timeout;
-  backoff->max_backoff = max_backoff;
-  backoff->rng_state = (uint32_t)gpr_now(GPR_CLOCK_REALTIME).tv_nsec;
-}
+namespace grpc_core {
 
-grpc_backoff_result grpc_backoff_begin(grpc_exec_ctx* exec_ctx,
-                                       grpc_backoff* backoff) {
-  backoff->current_backoff = backoff->initial_backoff;
-  const grpc_millis initial_timeout =
-      GPR_MAX(backoff->initial_backoff, backoff->min_connect_timeout);
-  const grpc_millis now = grpc_exec_ctx_now(exec_ctx);
-  const grpc_backoff_result result = {now + initial_timeout,
-                                      now + backoff->current_backoff};
-  return result;
+namespace {
+static double generate_uniform_random_number_between(double a, double b) {
+  if (a == b) return a;
+  if (a > b) GPR_SWAP(double, a, b);  // make sure a < b
+  const double range = b - a;
+  const double zero_to_one_rand = rand() / (double)RAND_MAX;
+  return a + zero_to_one_rand * range;
 }
+}  // namespace
 
-/* Generate a random number between 0 and 1. */
-static double generate_uniform_random_number(uint32_t* rng_state) {
-  *rng_state = (1103515245 * *rng_state + 12345) % ((uint32_t)1 << 31);
-  return *rng_state / (double)((uint32_t)1 << 31);
+Backoff::Backoff(const Options& options) : options_(options) {
+  seed = (unsigned int)gpr_now(GPR_CLOCK_REALTIME).tv_nsec;
 }
 
-static double generate_uniform_random_number_between(uint32_t* rng_state,
-                                                     double a, double b) {
-  if (a == b) return a;
-  if (a > b) GPR_SWAP(double, a, b);  // make sure a < b
-  const double range = b - a;
-  return a + generate_uniform_random_number(rng_state) * range;
+Backoff::Result Backoff::Begin(grpc_exec_ctx* exec_ctx) {
+  current_backoff_ = options_.initial_backoff();
+  const grpc_millis initial_timeout =
+      std::max(options_.initial_backoff(), options_.min_connect_timeout());
+  const grpc_millis now = grpc_exec_ctx_now(exec_ctx);
+  return Backoff::Result{now + initial_timeout, now + current_backoff_};
 }
 
-grpc_backoff_result grpc_backoff_step(grpc_exec_ctx* exec_ctx,
-                                      grpc_backoff* backoff) {
-  backoff->current_backoff = (grpc_millis)(GPR_MIN(
-      backoff->current_backoff * backoff->multiplier, backoff->max_backoff));
+Backoff::Result Backoff::Step(grpc_exec_ctx* exec_ctx) {
+  current_backoff_ =
+      (grpc_millis)(std::min(current_backoff_ * options_.multiplier(),
+                             (double)options_.max_backoff()));
   const double jitter = generate_uniform_random_number_between(
-      &backoff->rng_state, -backoff->jitter * backoff->current_backoff,
-      backoff->jitter * backoff->current_backoff);
-  const grpc_millis current_timeout =
-      GPR_MAX((grpc_millis)(backoff->current_backoff + jitter),
-              backoff->min_connect_timeout);
-  const grpc_millis next_timeout = GPR_MIN(
-      (grpc_millis)(backoff->current_backoff + jitter), backoff->max_backoff);
+      -options_.jitter() * current_backoff_,
+      options_.jitter() * current_backoff_);
+  const grpc_millis current_timeout = std::max(
+      (grpc_millis)(current_backoff_ + jitter), options_.min_connect_timeout());
+  const grpc_millis next_timeout = std::min(
+      (grpc_millis)(current_backoff_ + jitter), options_.max_backoff());
   const grpc_millis now = grpc_exec_ctx_now(exec_ctx);
-  const grpc_backoff_result result = {now + current_timeout,
-                                      now + next_timeout};
-  return result;
+  return Backoff::Result{now + current_timeout, now + next_timeout};
 }
 
-void grpc_backoff_reset(grpc_backoff* backoff) {
-  backoff->current_backoff = backoff->initial_backoff;
-}
+void Backoff::Reset() { current_backoff_ = options_.initial_backoff(); }
+
+void Backoff::SetRandomSeed(uint32_t seed) { srand(seed); }
+
+}  // namespace grpc_core

src/core/lib/backoff/backoff.h

@@ -21,63 +21,85 @@
 
 #include "src/core/lib/iomgr/exec_ctx.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-typedef struct {
-  /// const:  how long to wait after the first failure before retrying
-  grpc_millis initial_backoff;
-
-  /// const: factor with which to multiply backoff after a failed retry
-  double multiplier;
-
-  /// const: amount to randomize backoffs
-  double jitter;
-
-  /// const: minimum time between retries
-  grpc_millis min_connect_timeout;
-
-  /// const: maximum time between retries
-  grpc_millis max_backoff;
-
-  /// current delay before retries
-  grpc_millis current_backoff;
-
-  /// random number generator
-  uint32_t rng_state;
-} grpc_backoff;
-
-typedef struct {
+namespace grpc_core {
+
+class Backoff {
+ public:
+  class Options;
+  struct Result;
+
+  /// Initialize backoff machinery - does not need to be destroyed
+  explicit Backoff(const Options& options);
+
+  /// Begin retry loop: returns the deadlines to be used for the current attempt
+  /// and the subsequent retry, if any.
+  Result Begin(grpc_exec_ctx* exec_ctx);
+  /// Step a retry loop: returns the deadlines to be used for the current
+  /// attempt and the subsequent retry, if any.
+  Result Step(grpc_exec_ctx* exec_ctx);
+  /// Reset the backoff, so the next grpc_backoff_step will be a
+  /// grpc_backoff_begin.
+  void Reset();
+
+  void SetRandomSeed(unsigned int seed);
+
+  class Options {
+   public:
+    Options& set_initial_backoff(grpc_millis initial_backoff) {
+      initial_backoff_ = initial_backoff;
+      return *this;
+    }
+    Options& set_multiplier(double multiplier) {
+      multiplier_ = multiplier;
+      return *this;
+    }
+    Options& set_jitter(double jitter) {
+      jitter_ = jitter;
+      return *this;
+    }
+    Options& set_min_connect_timeout(grpc_millis min_connect_timeout) {
+      min_connect_timeout_ = min_connect_timeout;
+      return *this;
+    }
+    Options& set_max_backoff(grpc_millis max_backoff) {
+      max_backoff_ = max_backoff;
+      return *this;
+    }
+    /// how long to wait after the first failure before retrying
+    grpc_millis initial_backoff() const { return initial_backoff_; }
+    /// factor with which to multiply backoff after a failed retry
+    double multiplier() const { return multiplier_; }
+    /// amount to randomize backoffs
+    double jitter() const { return jitter_; }
+    /// minimum time between retries
+    grpc_millis min_connect_timeout() const { return min_connect_timeout_; }
+    /// maximum time between retries
+    grpc_millis max_backoff() const { return max_backoff_; }
+
+   private:
+    grpc_millis initial_backoff_;
+    double multiplier_;
+    double jitter_;
+    grpc_millis min_connect_timeout_;
+    grpc_millis max_backoff_;
+  };  // class Options
+
+  struct Result {
     /// Deadline to be used for the current attempt.
     grpc_millis current_deadline;
-
-  /// Deadline to be used for the next attempt, following the backoff strategy.
+    /// Deadline to be used for the next attempt, following the backoff
+    /// strategy.
     grpc_millis next_attempt_start_time;
-} grpc_backoff_result;
+  };
 
-/// Initialize backoff machinery - does not need to be destroyed
-void grpc_backoff_init(grpc_backoff* backoff, grpc_millis initial_backoff,
-                       double multiplier, double jitter,
-                       grpc_millis min_connect_timeout,
-                       grpc_millis max_backoff);
-
-/// Begin retry loop: returns the deadlines to be used for the current attempt
-/// and the subsequent retry, if any.
-grpc_backoff_result grpc_backoff_begin(grpc_exec_ctx* exec_ctx,
-                                       grpc_backoff* backoff);
-
-/// Step a retry loop: returns the deadlines to be used for the current attempt
-/// and the subsequent retry, if any.
-grpc_backoff_result grpc_backoff_step(grpc_exec_ctx* exec_ctx,
-                                      grpc_backoff* backoff);
+ private:
+  const Options options_;
+  /// current delay before retries
+  grpc_millis current_backoff_;
 
-/// Reset the backoff, so the next grpc_backoff_step will be a
-/// grpc_backoff_begin.
-void grpc_backoff_reset(grpc_backoff* backoff);
+  unsigned int seed;
+};
 
-#ifdef __cplusplus
-}
-#endif
+}  // namespace grpc_core
 
 #endif /* GRPC_CORE_LIB_BACKOFF_BACKOFF_H */

src/core/lib/support/alloc_new.h

@@ -0,0 +1,30 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_SUPPORT_ALLOC_NEW_H
+#define GRPC_SUPPORT_ALLOC_NEW_H
+
+#include <grpc/support/alloc.h>
+
+#define GPR_NEW(expr) new (gpr_zalloc) expr
+
+inline void* operator new(size_t sz, void* (*alloc_fn)(size_t)) {
+  return alloc_fn(sz);
+}
+
+#endif /* GRPC_SUPPORT_ALLOC_NEW_H */

test/core/backoff/backoff_test.cc

@@ -23,24 +23,32 @@
 
 #include "test/core/util/test_config.h"
 
+namespace grpc_core {
+namespace {
+
 static void test_constant_backoff(void) {
-  grpc_backoff backoff;
   const grpc_millis initial_backoff = 200;
   const double multiplier = 1.0;
   const double jitter = 0.0;
   const grpc_millis min_connect_timeout = 100;
   const grpc_millis max_backoff = 1000;
-  grpc_backoff_init(&backoff, initial_backoff, multiplier, jitter,
-                    min_connect_timeout, max_backoff);
+  Backoff::Options options;
+  options.set_initial_backoff(initial_backoff)
+      .set_multiplier(multiplier)
+      .set_jitter(jitter)
+      .set_min_connect_timeout(min_connect_timeout)
+      .set_max_backoff(max_backoff);
+  Backoff backoff(options);
+
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_backoff_result next_deadlines = grpc_backoff_begin(&exec_ctx, &backoff);
+  Backoff::Result next_deadlines = backoff.Begin(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline - grpc_exec_ctx_now(&exec_ctx) ==
              initial_backoff);
   GPR_ASSERT(next_deadlines.next_attempt_start_time -
                  grpc_exec_ctx_now(&exec_ctx) ==
              initial_backoff);
   for (int i = 0; i < 10000; i++) {
-    next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+    next_deadlines = backoff.Step(&exec_ctx);
     GPR_ASSERT(next_deadlines.current_deadline - grpc_exec_ctx_now(&exec_ctx) ==
                initial_backoff);
     GPR_ASSERT(next_deadlines.next_attempt_start_time -
@@ -52,16 +60,20 @@ static void test_constant_backoff(void) {
 }
 
 static void test_min_connect(void) {
-  grpc_backoff backoff;
   const grpc_millis initial_backoff = 100;
   const double multiplier = 1.0;
   const double jitter = 0.0;
   const grpc_millis min_connect_timeout = 200;
   const grpc_millis max_backoff = 1000;
-  grpc_backoff_init(&backoff, initial_backoff, multiplier, jitter,
-                    min_connect_timeout, max_backoff);
+  Backoff::Options options;
+  options.set_initial_backoff(initial_backoff)
+      .set_multiplier(multiplier)
+      .set_jitter(jitter)
+      .set_min_connect_timeout(min_connect_timeout)
+      .set_max_backoff(max_backoff);
+  Backoff backoff(options);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_backoff_result next = grpc_backoff_begin(&exec_ctx, &backoff);
+  Backoff::Result next = backoff.Begin(&exec_ctx);
   // Because the min_connect_timeout > initial_backoff, current_deadline is used
   // as the deadline for the current attempt.
   GPR_ASSERT(next.current_deadline - grpc_exec_ctx_now(&exec_ctx) ==
@@ -74,57 +86,61 @@ static void test_min_connect(void) {
 }
 
 static void test_no_jitter_backoff(void) {
-  grpc_backoff backoff;
   const grpc_millis initial_backoff = 2;
   const double multiplier = 2.0;
   const double jitter = 0.0;
   const grpc_millis min_connect_timeout = 1;
   const grpc_millis max_backoff = 513;
-  grpc_backoff_init(&backoff, initial_backoff, multiplier, jitter,
-                    min_connect_timeout, max_backoff);
+  Backoff::Options options;
+  options.set_initial_backoff(initial_backoff)
+      .set_multiplier(multiplier)
+      .set_jitter(jitter)
+      .set_min_connect_timeout(min_connect_timeout)
+      .set_max_backoff(max_backoff);
+  Backoff backoff(options);
   // x_1 = 2
   // x_n = 2**i + x_{i-1} ( = 2**(n+1) - 2 )
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   exec_ctx.now = 0;
   exec_ctx.now_is_valid = true;
-  grpc_backoff_result next_deadlines = grpc_backoff_begin(&exec_ctx, &backoff);
+  Backoff::Result next_deadlines = backoff.Begin(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline ==
              next_deadlines.next_attempt_start_time);
   GPR_ASSERT(next_deadlines.current_deadline == 2);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 6);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 14);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 30);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 62);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 126);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 254);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 510);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 1022);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   // Hit the maximum timeout. From this point onwards, retries will increase
   // only by max timeout.
   GPR_ASSERT(next_deadlines.current_deadline == 1535);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 2048);
   exec_ctx.now = next_deadlines.current_deadline;
-  next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+  next_deadlines = backoff.Step(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline == 2561);
   grpc_exec_ctx_finish(&exec_ctx);
 }
@@ -136,14 +152,18 @@ static void test_jitter_backoff(void) {
   const grpc_millis min_connect_timeout = 100;
   const double multiplier = 1.0;
   const double jitter = 0.1;
-  grpc_backoff backoff;
-  grpc_backoff_init(&backoff, initial_backoff, multiplier, jitter,
-                    min_connect_timeout, max_backoff);
+  Backoff::Options options;
+  options.set_initial_backoff(initial_backoff)
+      .set_multiplier(multiplier)
+      .set_jitter(jitter)
+      .set_min_connect_timeout(min_connect_timeout)
+      .set_max_backoff(max_backoff);
+  Backoff backoff(options);
 
-  backoff.rng_state = 0;  // force consistent PRNG
+  backoff.SetRandomSeed(0);  // force consistent PRNG
 
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_backoff_result next_deadlines = grpc_backoff_begin(&exec_ctx, &backoff);
+  Backoff::Result next_deadlines = backoff.Begin(&exec_ctx);
   GPR_ASSERT(next_deadlines.current_deadline - grpc_exec_ctx_now(&exec_ctx) ==
              initial_backoff);
   GPR_ASSERT(next_deadlines.next_attempt_start_time -
@@ -156,7 +176,7 @@ static void test_jitter_backoff(void) {
       (grpc_millis)((double)current_backoff * (1 + jitter));
 
   for (int i = 0; i < 10000; i++) {
-    next_deadlines = grpc_backoff_step(&exec_ctx, &backoff);
+    next_deadlines = backoff.Step(&exec_ctx);
     // next-now must be within (jitter*100)% of the current backoff (which
     // increases by * multiplier up to max_backoff).
     const grpc_millis timeout_millis =
@@ -173,15 +193,17 @@ static void test_jitter_backoff(void) {
   }
   grpc_exec_ctx_finish(&exec_ctx);
 }
+}  // namespace
+}  // namespace grpc_core
 
 int main(int argc, char** argv) {
   grpc_test_init(argc, argv);
   gpr_time_init();
 
-  test_constant_backoff();
-  test_min_connect();
-  test_no_jitter_backoff();
-  test_jitter_backoff();
+  grpc_core::test_constant_backoff();
+  grpc_core::test_min_connect();
+  grpc_core::test_no_jitter_backoff();
+  grpc_core::test_jitter_backoff();
 
   return 0;
 }