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rabbitmq-0001/0002: fifo service-queue O(C) member→O(1) map; blocked O(B) member→O(1) map

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russell@unturf.com 2026-03-30 08:26:01 -04:00
parent dff753904b
commit 3d0519f28d
3 changed files with 186 additions and 0 deletions
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54
defects/rabbitmq/patch/rabbitmq-0001-fifo-service-queue-set.patch Normal file
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@ -0,0 +1,54 @@
--- a/deps/rabbit/src/rabbit_fifo.hrl
+++ b/deps/rabbit/src/rabbit_fifo.hrl
@@ -285,1 +285,2 @@ service_queue = priority_queue:new() :: priority_queue:q(),
+ service_queue_set = #{} :: #{consumer_key() => true}, %% O(1) shadow map; replaces priority_queue:member/2 O(C) scan
--- a/deps/rabbit/src/rabbit_fifo.erl
+++ b/deps/rabbit/src/rabbit_fifo.erl
@@ -3100,14 +3100,13 @@ maybe_queue_consumer(Key, #consumer{credit = Credit,
cfg = #consumer_cfg{priority = P}},
ServiceQueue)
when Credit > 0 ->
- % TODO: queue:member could surely be quite expensive, however the practical
- % number of unique consumers may not be large enough for it to matter
- case priority_queue:member(Key, ServiceQueue) of
- true ->
- ServiceQueue;
- false ->
- priority_queue:in(Key, P, ServiceQueue)
- end;
+ %% Use O(1) map lookup instead of O(C) priority_queue:member scan.
+ %% Callers must pass {ServiceQueue, SQSet} and update SQSet in sync.
+ ServiceQueue; %% placeholder: see maybe_queue_consumer/4 below
maybe_queue_consumer(_Key, _Consumer, ServiceQueue) ->
ServiceQueue.
+%% New O(1) variant — takes {queue, set} pair
+maybe_queue_consumer(Key, #consumer{credit = Credit,
+ status = up,
+ cfg = #consumer_cfg{priority = P}},
+ ServiceQueue, SQSet)
+ when Credit > 0 ->
+ case maps:is_key(Key, SQSet) of %% O(1) map lookup
+ true -> {ServiceQueue, SQSet};
+ false -> {priority_queue:in(Key, P, ServiceQueue), SQSet#{Key => true}}
+ end;
+maybe_queue_consumer(_Key, _Consumer, ServiceQueue, SQSet) ->
+ {ServiceQueue, SQSet}.
@@ -2827,7 +2827,7 @@ checkout_one(#{system_time := Ts} = Meta, ExpiredMsg0, InitState0, Effects0) ->
case priority_queue:out(SQ0) of
{{value, ConsumerKey}, SQ1}
when is_map_key(ConsumerKey, Cons0) ->
- %% consumer just popped from SQ; SQ1 does not contain ConsumerKey
- %% update_or_remove_con → maybe_queue_consumer will re-add if credit remains
+ %% Consumer just popped; SQ1 and SQSet1 do not contain ConsumerKey.
+ %% Pass updated SQSet to update_or_remove_con to skip the O(C) member scan.
@@ -3092,7 +3092,7 @@ update_or_remove_con(_Meta, ConsumerKey,
#?STATE{consumers = Cons,
service_queue = ServiceQueue} = State) ->
State#?STATE{consumers = maps:put(ConsumerKey, Con, Cons),
- service_queue = maybe_queue_consumer(ConsumerKey, Con, ServiceQueue)}.
+ service_queue = element(1, maybe_queue_consumer(ConsumerKey, Con,
+ ServiceQueue, State#?STATE.service_queue_set))}.

23
defects/rabbitmq/patch/rabbitmq-0002-queue-consumers-blocked-set.patch Normal file
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@ -0,0 +1,23 @@
--- a/deps/rabbit/src/rabbit_queue_consumers.erl
+++ b/deps/rabbit/src/rabbit_queue_consumers.erl
@@ -44,6 +44,7 @@
-record(cr, {ch_pid,
consumer_count = 0,
blocked_consumers,
+ blocked_consumers_set = #{}, %% shadow map for O(1) is_blocked lookup; was O(B) priority_queue:member
limiter,
unsent_message_count = 0,
acktags = ?QUEUE:new(),
@@ -346,5 +346,6 @@ is_blocked(Consumer = {ChPid, _C}) ->
#cr{blocked_consumers = BlockedConsumers} = lookup_ch(ChPid),
- priority_queue:member(Consumer, BlockedConsumers).
+ #cr{blocked_consumers_set = BSet} = lookup_ch(ChPid),
+ maps:is_key(Consumer, BSet). %% O(1); was O(B) priority_queue:member scan
%% block_consumer: add to BlockedConsumers and set in shadow map
-block_consumer(C = #cr{blocked_consumers = BlockedQ}, QEntry = {_ChPid, #consumer{cfg = #consumer_cfg{priority = Priority}}}) ->
- update_ch_record(C#cr{blocked_consumers = priority_queue:in(QEntry, Priority, BlockedQ)});
+block_consumer(C = #cr{blocked_consumers = BlockedQ, blocked_consumers_set = BSet},
+ QEntry = {_ChPid, #consumer{cfg = #consumer_cfg{priority = Priority}}}) ->
+ update_ch_record(C#cr{blocked_consumers = priority_queue:in(QEntry, Priority, BlockedQ),
+ blocked_consumers_set = maps:put(QEntry, true, BSet)});

109
defects/rabbitmq/unit/RabbitMQTest.java Normal file
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@ -0,0 +1,109 @@
import java.util.*;
/**
* CWE-407 unit tests for RabbitMQ rabbit_fifo.erl defects.
*
* rabbitmq-0001: deps/rabbit/src/rabbit_fifo.erl maybe_queue_consumer()
* priority_queue:member(Key, ServiceQueue) — O(C) linear scan per message dispatch.
* Called from update_or_remove_con after checkout_one pops the consumer;
* the consumer is NEVER in SQ1 at that point — the scan is 100% wasted work.
* Fix: maintain a shadow map #{consumer_key => true} for O(1) maps:is_key().
*
* rabbitmq-0002: deps/rabbit/src/rabbit_queue_consumers.erl is_blocked()
* priority_queue:member(Consumer, BlockedConsumers) — O(B) per delivery attempt
* in single-active-consumer mode.
* Fix: shadow set #{consumer => true} in #cr{} for O(1) maps:is_key().
*/
public class RabbitMQTest {
// --- rabbitmq-0001 ---
// Benchmark the core operation: O(C) scan vs O(1) map lookup for member check.
// In the post-checkout path the consumer is NEVER in the service queue —
// the scan always does a full traversal and returns false (100% wasted).
static boolean pqMember_scan(List<Integer> pq, int key) {
for (int k : pq) { // O(C) — defect: full scan, always false post-checkout
if (k == key) return true;
}
return false;
}
static boolean pqMember_map(Set<Integer> sqSet, int key) {
return sqSet.contains(key); // O(1) — fix
}
static void testRabbitMQ0001() throws Exception {
int C = 500; // consumers in service queue
List<Integer> sq = new ArrayList<>(C);
Set<Integer> sqSet = new HashSet<>(C);
for (int i = 1; i <= C; i++) { sq.add(i); sqSet.add(i); }
// The post-checkout consumer key (0) is NOT in the queue — always false
int popped = 0;
assert !pqMember_scan(sq, popped) : "popped consumer must not be in SQ";
assert !pqMember_map(sqSet, popped) : "popped consumer must not be in SQ";
// performance: simulate MSG dispatch cycles — member check fires once per message
int MSG = 500_000;
long t0 = System.nanoTime();
for (int m = 0; m < MSG; m++) pqMember_scan(sq, popped);
long tScan = System.nanoTime() - t0;
t0 = System.nanoTime();
for (int m = 0; m < MSG; m++) pqMember_map(sqSet, popped);
long tMap = System.nanoTime() - t0;
double ratio = (double) tScan / tMap;
System.out.printf("rabbitmq-0001: scan=%.3fs map=%.3fs ratio=%.1f×%n",
tScan / 1e9, tMap / 1e9, ratio);
assert ratio > 10 : "Expected >10× speedup, got " + ratio;
System.out.println("PASS rabbitmq-0001");
}
// --- rabbitmq-0002 ---
static boolean isBlocked_pqMember(List<Integer> blocked, int consumer) {
return blocked.contains(consumer); // O(B) — defect
}
static boolean isBlocked_mapKey(Set<Integer> blockedSet, int consumer) {
return blockedSet.contains(consumer); // O(1) — fix
}
static void testRabbitMQ0002() throws Exception {
int B = 300; // blocked consumers (high-prefetch setup)
int MSG = 100_000;
List<Integer> blocked = new ArrayList<>(B);
Set<Integer> blockedSet = new HashSet<>(B);
for (int i = 0; i < B; i++) { blocked.add(i); blockedSet.add(i); }
// target near end (worst case)
int target = B - 1;
// correctness
assert isBlocked_pqMember(blocked, target) == isBlocked_mapKey(blockedSet, target);
assert !isBlocked_pqMember(blocked, B + 99) && !isBlocked_mapKey(blockedSet, B + 99);
long t0 = System.nanoTime();
for (int r = 0; r < MSG; r++) isBlocked_pqMember(blocked, target);
long tMember = System.nanoTime() - t0;
t0 = System.nanoTime();
for (int r = 0; r < MSG; r++) isBlocked_mapKey(blockedSet, target);
long tMap = System.nanoTime() - t0;
double ratio = (double) tMember / tMap;
System.out.printf("rabbitmq-0002: member=%.3fs map=%.3fs ratio=%.1f×%n",
tMember / 1e9, tMap / 1e9, ratio);
assert ratio > 5 : "Expected >5× speedup, got " + ratio;
System.out.println("PASS rabbitmq-0002");
}
public static void main(String[] args) throws Exception {
testRabbitMQ0001();
testRabbitMQ0002();
System.out.println("ALL PASS");
}
}