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feat: P2-3 repl_wait_ack() with pthread_cond_timedwait + ACK deadlock prevention

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Implements sync replication wait: primary blocks until at least one non-catching-up
standby ACKs the target LSN, or times out. Uses pthread_cond_timedwait with
CLOCK_REALTIME deadline. Inner loop rechecks all standbys after each wakeup to
guard against spurious wakeups.

ACK deadlock prevention: repl_on_ack() is called exclusively from the io_worker
read callback (not vtaskmgr), so it only does atomic_store + pthread_cond_signal —
safe to call while vcpu threads block in repl_wait_ack().

4 new TDD tests (all green, 9 total in test_repl_unit):
- test_wait_ack_no_standbys_returns_enodev
- test_wait_ack_already_acked
- test_wait_ack_timeout (verifies >=80ms elapsed)
- test_wait_ack_woken_by_background_ack (pthread thread signals after 30ms)
This commit is contained in:
Rongsong Shen 2026-05-07 17:23:50 +00:00
parent abefc8a128
commit d326ee1b2e
2 changed files with 144 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

90
src/controller/testsuite/test_repl_unit.c
View file

@ -1,7 +1,10 @@
#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <pthread.h>
#include <time.h>
/* Use the same Unity include pattern as other controller tests */
#include <unity/unity.h>
#include "repl.h"
@ -74,6 +77,89 @@ static void test_repl_trim_lsn_disconnected_slot_expiry(void) {
printf("test_repl_trim_lsn_disconnected_slot_expiry: PASS\n");
}
/* ============================================================
* P2-3: repl_wait_ack() tests
* ============================================================ */
/* Test 1: repl_wait_ack returns -ENODEV when no standbys connected */
static void test_wait_ack_no_standbys_returns_enodev(void) {
replicator_t r;
repl_init(&r);
int rc = repl_wait_ack(&r, /*target_lsn=*/10, /*timeout_ms=*/50);
TEST_ASSERT_EQUAL_INT(-ENODEV, rc);
repl_fini(&r);
printf("test_wait_ack_no_standbys_returns_enodev: PASS\n");
}
/* Test 2: repl_wait_ack returns 0 when standby already ACKed target LSN */
static void test_wait_ack_already_acked(void) {
replicator_t r;
int dummy_ep = 0;
repl_init(&r);
repl_add_standby(&r, (void*)&dummy_ep, "sb", 7001);
/* Pre-set acked_lsn to 20 (already past target 10) */
repl_on_ack(&r, (void*)&dummy_ep, 20);
int rc = repl_wait_ack(&r, 10, 50);
TEST_ASSERT_EQUAL_INT(0, rc);
repl_fini(&r);
printf("test_wait_ack_already_acked: PASS\n");
}
/* Test 3: repl_wait_ack times out when standby never ACKs */
static void test_wait_ack_timeout(void) {
replicator_t r;
int dummy_ep = 0;
repl_init(&r);
repl_add_standby(&r, (void*)&dummy_ep, "sb", 7001);
/* acked_lsn stays at 0 — never reaches target 100 */
struct timespec start, end;
clock_gettime(CLOCK_MONOTONIC, &start);
int rc = repl_wait_ack(&r, 100, 100 /* 100ms timeout */);
clock_gettime(CLOCK_MONOTONIC, &end);
TEST_ASSERT_EQUAL_INT(-ETIMEDOUT, rc);
/* Verify we actually waited ~100ms (not returned immediately) */
long elapsed_ms = (end.tv_sec - start.tv_sec) * 1000
+ (end.tv_nsec - start.tv_nsec) / 1000000;
TEST_ASSERT_TRUE(elapsed_ms >= 80); /* at least 80ms */
repl_fini(&r);
printf("test_wait_ack_timeout: PASS\n");
}
/* Test 4: ACK from background thread wakes repl_wait_ack */
struct ack_args {
replicator_t *r;
void *ep;
uint64_t lsn;
int delay_ms;
};
static void* ack_sender_thread(void* arg) {
struct ack_args* a = arg;
struct timespec ts = { 0, (long)a->delay_ms * 1000000L };
nanosleep(&ts, NULL);
repl_on_ack(a->r, a->ep, a->lsn);
return NULL;
}
static void test_wait_ack_woken_by_background_ack(void) {
replicator_t r;
int dummy_ep = 0;
repl_init(&r);
repl_add_standby(&r, (void*)&dummy_ep, "sb", 7001);
struct ack_args args = { &r, (void*)&dummy_ep, 15, 30 /* 30ms delay */ };
pthread_t th;
pthread_create(&th, NULL, ack_sender_thread, &args);
/* Wait for LSN 15 with 200ms timeout — ACK arrives after 30ms */
int rc = repl_wait_ack(&r, 15, 200);
pthread_join(th, NULL);
TEST_ASSERT_EQUAL_INT(0, rc);
repl_fini(&r);
printf("test_wait_ack_woken_by_background_ack: PASS\n");
}
void test_repl_unit(void) {
UNITY_BEGIN();
RUN_TEST(test_repl_init_zeroes_nstandbys);
@ -81,5 +167,9 @@ void test_repl_unit(void) {
RUN_TEST(test_repl_add_standby_max);
RUN_TEST(test_repl_trim_lsn_no_standbys);
RUN_TEST(test_repl_trim_lsn_disconnected_slot_expiry);
RUN_TEST(test_wait_ack_no_standbys_returns_enodev);
RUN_TEST(test_wait_ack_already_acked);
RUN_TEST(test_wait_ack_timeout);
RUN_TEST(test_wait_ack_woken_by_background_ack);
UNITY_END();
}