diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/rabbit_priority_queue.erl | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/src/rabbit_priority_queue.erl b/src/rabbit_priority_queue.erl index eabf289d65..9ad5493a88 100644 --- a/src/rabbit_priority_queue.erl +++ b/src/rabbit_priority_queue.erl @@ -20,6 +20,8 @@ -include_lib("rabbit_framing.hrl"). -behaviour(rabbit_backing_queue). +%% enabled unconditionally. Disabling priority queueing after +%% it has been enabled is dangerous. -rabbit_boot_step({?MODULE, [{description, "enable priority queue"}, {mfa, {?MODULE, enable, []}}, @@ -49,6 +51,23 @@ -define(passthrough3(F), {Res1, Res2, BQS1} = BQ:F, {Res1, Res2, State#passthrough{bqs = BQS1}}). +%% This module adds suport for priority queues. +%% +%% Priority queues have one backing queue per priority. Backing queue functions +%% then produce a list of results for each BQ and fold over them, sorting +%% by priority. +%% +%%For queues that do not +%% have priorities enabled, the functions in this module delegate to +%% their "regular" backing queue module counterparts. See the `passthrough` +%% record and passthrough{1,2,3} macros. +%% +%% Delivery to consumers happens by first "running" the queue with +%% the highest priority until there are no more messages to deliver, +%% then the next one, and so on. This offers good prioritisation +%% but may result in lower priority messages not being delivered +%% when there's a high ingress rate of messages with higher priority. + enable() -> {ok, RealBQ} = application:get_env(rabbit, backing_queue_module), case RealBQ of @@ -495,6 +514,7 @@ bq_store(P, BQS, BQSs) -> _ -> BQSN end} || {PN, BQSN} <- BQSs]. +%% a(State = #state{bqss = BQSs}) -> Ps = [P || {P, _} <- BQSs], case lists:reverse(lists:usort(Ps)) of |