diff options
Diffstat (limited to 'src/core')
| -rw-r--r-- | src/core/ext/lb_policy/round_robin/round_robin.c | 40 |
1 files changed, 33 insertions, 7 deletions
diff --git a/src/core/ext/lb_policy/round_robin/round_robin.c b/src/core/ext/lb_policy/round_robin/round_robin.c index dcdc0c6285..a73ab0a4a6 100644 --- a/src/core/ext/lb_policy/round_robin/round_robin.c +++ b/src/core/ext/lb_policy/round_robin/round_robin.c @@ -31,6 +31,34 @@ * */ +/** Round Robin Policy. + * + * This policy keeps: + * - A circular list of ready (connected) subchannels, the + * *readylist*. An empty readylist consists solely of its root (dummy) node. + * - A pointer to the last element picked from the readylist, the *lastpick*. + * Initially set to point to the readylist's root. + * + * Behavior: + * - When a subchannel connects, it's *prepended* to the readylist's root node. + * Ie, if readylist = A <-> B <-> ROOT <-> C + * ^ ^ + * |____________________| + * and subchannel D becomes connected, the addition of D to the readylist + * results in readylist = A <-> B <-> D <-> ROOT <-> C + * ^ ^ + * |__________________________| + * - When a subchannel disconnects, it's removed from the readylist. If the + * subchannel being removed was the most recently picked, the *lastpick* + * pointer moves to the removed node's previous element. Note that if the + * readylist only had one element, this is still legal, as the lastpick would + * point to the dummy root node, for an empty readylist. + * - Upon picking, *lastpick* is updated to point to the returned (connected) + * subchannel. Note that it possible that the selected subchannel becomes + * disconnected in the interim between the selection and the actual usage of + * the subchannel by the caller. + */ + #include <string.h> #include <grpc/support/alloc.h> @@ -173,9 +201,7 @@ static void remove_disconnected_sc_locked(round_robin_lb_policy *p, return; } if (node == p->ready_list_last_pick) { - /* If removing the lastly picked node, reset the last pick pointer to the - * dummy root of the list */ - p->ready_list_last_pick = &p->ready_list; + p->ready_list_last_pick = p->ready_list_last_pick->prev; } /* removing last item */ @@ -344,8 +370,8 @@ static int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, *target = grpc_subchannel_get_connected_subchannel(selected->subchannel); if (grpc_lb_round_robin_trace) { gpr_log(GPR_DEBUG, - "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)", - selected->subchannel, selected); + "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)", *target, + selected); } /* only advance the last picked pointer if the selection was used */ advance_last_picked_locked(p); @@ -524,7 +550,7 @@ static void round_robin_factory_ref(grpc_lb_policy_factory *factory) {} static void round_robin_factory_unref(grpc_lb_policy_factory *factory) {} -static grpc_lb_policy *create_round_robin(grpc_exec_ctx *exec_ctx, +static grpc_lb_policy *round_robin_create(grpc_exec_ctx *exec_ctx, grpc_lb_policy_factory *factory, grpc_lb_policy_args *args) { GPR_ASSERT(args->addresses != NULL); @@ -580,7 +606,7 @@ static grpc_lb_policy *create_round_robin(grpc_exec_ctx *exec_ctx, } static const grpc_lb_policy_factory_vtable round_robin_factory_vtable = { - round_robin_factory_ref, round_robin_factory_unref, create_round_robin, + round_robin_factory_ref, round_robin_factory_unref, round_robin_create, "round_robin"}; static grpc_lb_policy_factory round_robin_lb_policy_factory = { |