Integrate backoff library with subchannel

src/core/client_config/subchannel.c

@@ -45,6 +45,7 @@
 #include "src/core/client_config/subchannel_index.h"
 #include "src/core/iomgr/timer.h"
 #include "src/core/profiling/timers.h"
+#include "src/core/support/backoff.h"
 #include "src/core/surface/channel.h"
 #include "src/core/transport/connectivity_state.h"
 
@@ -127,8 +128,8 @@ struct grpc_subchannel {
 
   /** next connect attempt time */
   gpr_timespec next_attempt;
-  /** amount to backoff each failure */
+  /** backoff state */
-  gpr_timespec backoff_delta;
+  gpr_backoff backoff_state;
   /** do we have an active alarm? */
   int have_alarm;
   /** our alarm */
@@ -146,7 +147,6 @@ struct grpc_subchannel_call {
 #define CALLSTACK_TO_SUBCHANNEL_CALL(callstack) \
   (((grpc_subchannel_call *)(callstack)) - 1)
 
-static gpr_timespec compute_connect_deadline(grpc_subchannel *c);
 static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *subchannel,
                                  bool iomgr_success);
 
@@ -184,8 +184,8 @@ static void connection_destroy(grpc_exec_ctx *exec_ctx, void *arg,
   gpr_free(c);
 }
 
-void grpc_connected_subchannel_ref(grpc_connected_subchannel *c
+void grpc_connected_subchannel_ref(
-                                       GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+    grpc_connected_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   GRPC_CHANNEL_STACK_REF(CHANNEL_STACK_FROM_CONNECTION(c), REF_REASON);
 }
 
@@ -226,8 +226,8 @@ static gpr_atm ref_mutate(grpc_subchannel *c, gpr_atm delta,
   return old_val;
 }
 
-grpc_subchannel *grpc_subchannel_ref(grpc_subchannel *c
+grpc_subchannel *grpc_subchannel_ref(
-                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   gpr_atm old_refs;
   old_refs = ref_mutate(c, (1 << INTERNAL_REF_BITS),
                         0 REF_MUTATE_PURPOSE("STRONG_REF"));
@@ -235,8 +235,8 @@ grpc_subchannel *grpc_subchannel_ref(grpc_subchannel *c
   return c;
 }
 
-grpc_subchannel *grpc_subchannel_weak_ref(grpc_subchannel *c
+grpc_subchannel *grpc_subchannel_weak_ref(
-                                              GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   gpr_atm old_refs;
   old_refs = ref_mutate(c, 1, 0 REF_MUTATE_PURPOSE("WEAK_REF"));
   GPR_ASSERT(old_refs != 0);
@@ -337,6 +337,22 @@ grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
   grpc_closure_init(&c->connected, subchannel_connected, c);
   grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
                                "subchannel");
+  gpr_backoff_init(&c->backoff_state,
+                   GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
+                   GRPC_SUBCHANNEL_RECONNECT_JITTER,
+                   GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000,
+                   GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  if (c->args) {
+    for (size_t i = 0; i < c->args->num_args; i++) {
+      if (0 == strcmp(c->args->args[i].key,
+                      "grpc.testing.fixed_reconnect_backoff")) {
+        GPR_ASSERT(c->args->args[i].type == GRPC_ARG_INTEGER);
+        gpr_backoff_init(&c->backoff_state, 1.0, 0.0,
+                         c->args->args[i].value.integer,
+                         c->args->args[i].value.integer);
+      }
+    }
+  }
   gpr_mu_init(&c->mu);
 
   return grpc_subchannel_index_register(exec_ctx, key, c);
@@ -348,7 +364,7 @@ static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   args.interested_parties = c->pollset_set;
   args.addr = c->addr;
   args.addr_len = c->addr_len;
-  args.deadline = compute_connect_deadline(c);
+  args.deadline = c->next_attempt;
   args.channel_args = c->args;
   args.initial_connect_string = c->initial_connect_string;
 
@@ -359,10 +375,8 @@ static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
 }
 
 static void start_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
-  c->backoff_delta = gpr_time_from_seconds(
-      GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS, GPR_TIMESPAN);
   c->next_attempt =
-      gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), c->backoff_delta);
+      gpr_backoff_begin(&c->backoff_state, gpr_now(GPR_CLOCK_MONOTONIC));
   continue_connect(exec_ctx, c);
 }
 
@@ -579,50 +593,6 @@ static void publish_transport(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   gpr_free((void *)filters);
 }
 
-/* Generate a random number between 0 and 1. */
-static double generate_uniform_random_number(grpc_subchannel *c) {
-  c->random = (1103515245 * c->random + 12345) % ((uint32_t)1 << 31);
-  return c->random / (double)((uint32_t)1 << 31);
-}
-
-/* Update backoff_delta and next_attempt in subchannel */
-static void update_reconnect_parameters(grpc_subchannel *c) {
-  size_t i;
-  int32_t backoff_delta_millis, jitter;
-  int32_t max_backoff_millis =
-      GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000;
-  double jitter_range;
-
-  if (c->args) {
-    for (i = 0; i < c->args->num_args; i++) {
-      if (0 == strcmp(c->args->args[i].key,
-                      "grpc.testing.fixed_reconnect_backoff")) {
-        GPR_ASSERT(c->args->args[i].type == GRPC_ARG_INTEGER);
-        c->next_attempt = gpr_time_add(
-            gpr_now(GPR_CLOCK_MONOTONIC),
-            gpr_time_from_millis(c->args->args[i].value.integer, GPR_TIMESPAN));
-        return;
-      }
-    }
-  }
-
-  backoff_delta_millis =
-      (int32_t)(gpr_time_to_millis(c->backoff_delta) *
-                GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER);
-  if (backoff_delta_millis > max_backoff_millis) {
-    backoff_delta_millis = max_backoff_millis;
-  }
-  c->backoff_delta = gpr_time_from_millis(backoff_delta_millis, GPR_TIMESPAN);
-  c->next_attempt =
-      gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), c->backoff_delta);
-
-  jitter_range = GRPC_SUBCHANNEL_RECONNECT_JITTER * backoff_delta_millis;
-  jitter =
-      (int32_t)((2 * generate_uniform_random_number(c) - 1) * jitter_range);
-  c->next_attempt =
-      gpr_time_add(c->next_attempt, gpr_time_from_millis(jitter, GPR_TIMESPAN));
-}
-
 static void on_alarm(grpc_exec_ctx *exec_ctx, void *arg, bool iomgr_success) {
   grpc_subchannel *c = arg;
   gpr_mu_lock(&c->mu);
@@ -631,7 +601,8 @@ static void on_alarm(grpc_exec_ctx *exec_ctx, void *arg, bool iomgr_success) {
     iomgr_success = 0;
   }
   if (iomgr_success) {
-    update_reconnect_parameters(c);
+    c->next_attempt =
+        gpr_backoff_step(&c->backoff_state, gpr_now(GPR_CLOCK_MONOTONIC));
     continue_connect(exec_ctx, c);
     gpr_mu_unlock(&c->mu);
   } else {
@@ -661,17 +632,6 @@ static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *arg,
   }
 }
 
-static gpr_timespec compute_connect_deadline(grpc_subchannel *c) {
-  gpr_timespec current_deadline =
-      gpr_time_add(c->next_attempt, c->backoff_delta);
-  gpr_timespec min_deadline = gpr_time_add(
-      gpr_now(GPR_CLOCK_MONOTONIC),
-      gpr_time_from_seconds(GRPC_SUBCHANNEL_MIN_CONNECT_TIMEOUT_SECONDS,
-                            GPR_TIMESPAN));
-  return gpr_time_cmp(current_deadline, min_deadline) > 0 ? current_deadline
-                                                          : min_deadline;
-}
-
 /*
  * grpc_subchannel_call implementation
  */
@@ -686,8 +646,8 @@ static void subchannel_call_destroy(grpc_exec_ctx *exec_ctx, void *call,
   GPR_TIMER_END("grpc_subchannel_call_unref.destroy", 0);
 }
 
-void grpc_subchannel_call_ref(grpc_subchannel_call *c
+void grpc_subchannel_call_ref(
-                                  GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+    grpc_subchannel_call *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   GRPC_CALL_STACK_REF(SUBCHANNEL_CALL_TO_CALL_STACK(c), REF_REASON);
 }