reconnect support

1 files changed, 53 insertions, 10 deletions

diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index 074e64dfc5..5cf56d33eb 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -44,6 +44,12 @@
 #include "src/core/transport/connectivity_state.h"
 #include "src/core/surface/channel.h"
 
+#define GRPC_SUBCHANNEL_MIN_CONNECT_TIMEOUT_SECONDS 20
+#define GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS 1
+#define GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER 1.6
+#define GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS 120
+#define GRPC_SUBCHANNEL_RECONNECT_JITTER 0.2
+
 typedef struct {
   /* all fields protected by subchannel->mu */
   /** refcount */
@@ -125,6 +131,8 @@ struct grpc_subchannel {
   int have_alarm;
   /** our alarm */
   grpc_alarm alarm;
+  /** current random value */
+  gpr_int32 random;
 };
 
 struct grpc_subchannel_call {
@@ -264,6 +272,10 @@ void grpc_subchannel_del_interested_party(grpc_subchannel *c,
   grpc_pollset_set_del_pollset(c->pollset_set, pollset);
 }
 
+static gpr_int32 random_seed() {
+  return gpr_time_to_millis(gpr_now(GPR_CLOCK_REALTIME));
+}
+
 grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
                                         grpc_subchannel_args *args) {
   grpc_subchannel *c = gpr_malloc(sizeof(*c));
@@ -284,6 +296,7 @@ grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
   c->mdctx = args->mdctx;
   c->master = args->master;
   c->pollset_set = grpc_client_channel_get_connecting_pollset_set(parent_elem);
+  c->random = random_seed();
   grpc_mdctx_ref(c->mdctx);
   grpc_iomgr_closure_init(&c->connected, subchannel_connected, c);
   grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
@@ -307,10 +320,9 @@ static void continue_connect(grpc_subchannel *c) {
 }
 
 static void start_connect(grpc_subchannel *c) {
-  gpr_timespec now = gpr_now(GPR_CLOCK_REALTIME);
-  c->next_attempt = now;
-  c->backoff_delta = gpr_time_from_seconds(1, GPR_TIMESPAN);
-
+  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_REALTIME), c->backoff_delta);
   continue_connect(c);
 }
 
@@ -576,6 +588,34 @@ static void publish_transport(grpc_subchannel *c) {
   }
 }
 
+/* Generate a random number between 0 and 1. */
+static double generate_uniform_random_number(grpc_subchannel *c) {
+  c->random = (1103515245 * c->random + 12345) % ((gpr_uint32)1 << 31);
+  return c->random / (double)((gpr_uint32)1 << 31);
+}
+
+/* Update backoff_delta and next_attempt in subchannel */
+static void update_reconnect_parameters(grpc_subchannel *c) {
+  gpr_int32 backoff_delta_millis, jitter;
+  gpr_int32 max_backoff_millis =
+      GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000;
+  double jitter_range;
+  backoff_delta_millis =
+      (gpr_int32)(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_REALTIME), c->backoff_delta);
+
+  jitter_range = GRPC_SUBCHANNEL_RECONNECT_JITTER * backoff_delta_millis;
+  jitter =
+      (gpr_int32)((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(void *arg, int iomgr_success) {
   grpc_subchannel *c = arg;
   gpr_mu_lock(&c->mu);
@@ -586,6 +626,7 @@ static void on_alarm(void *arg, int iomgr_success) {
   connectivity_state_changed_locked(c, "alarm");
   gpr_mu_unlock(&c->mu);
   if (iomgr_success) {
+    update_reconnect_parameters(c);
     continue_connect(c);
   } else {
     GRPC_CHANNEL_INTERNAL_UNREF(c->master, "connecting");
@@ -603,18 +644,20 @@ static void subchannel_connected(void *arg, int iomgr_success) {
     GPR_ASSERT(!c->have_alarm);
     c->have_alarm = 1;
     connectivity_state_changed_locked(c, "connect_failed");
-    c->next_attempt = gpr_time_add(c->next_attempt, c->backoff_delta);
-    if (gpr_time_cmp(c->backoff_delta,
-                     gpr_time_from_seconds(60, GPR_TIMESPAN)) < 0) {
-      c->backoff_delta = gpr_time_add(c->backoff_delta, c->backoff_delta);
-    }
     grpc_alarm_init(&c->alarm, c->next_attempt, on_alarm, c, now);
     gpr_mu_unlock(&c->mu);
   }
 }
 
 static gpr_timespec compute_connect_deadline(grpc_subchannel *c) {
-  return gpr_time_add(c->next_attempt, c->backoff_delta);
+  gpr_timespec current_deadline =
+      gpr_time_add(c->next_attempt, c->backoff_delta);
+  gpr_timespec min_deadline = gpr_time_add(
+      gpr_now(GPR_CLOCK_REALTIME),
+      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;
 }
 
 static grpc_connectivity_state compute_connectivity_locked(grpc_subchannel *c) {