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Fix shard map reload mechanism

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This commit is contained in:
Konstantin Knizhnik
2023-12-01 20:30:49 +02:00
parent 38f64ea8ef
commit 864d5f84e9
2 changed files with 15 additions and 9 deletions
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23
pgxn/neon/libpagestore.c
View File

@@ -61,6 +61,7 @@ bool (*old_redo_read_buffer_filter) (XLogReaderState *record, uint8 block_id) =
static bool pageserver_flush(shardno_t shard_no);
static void pageserver_disconnect(shardno_t shard_no);
static void AssignPageserverConnstring(const char *newval, void *extra);
static shmem_startup_hook_type prev_shmem_startup_hook;
#if PG_VERSION_NUM>=150000
@@ -112,6 +113,7 @@ psm_shmem_startup(void)
{
shard_map->n_shards = 0;
pg_atomic_init_u64(&shard_map->update_counter, 0);
AssignPageserverConnstring(page_server_connstring, NULL);
}
LWLockRelease(AddinShmemInitLock);
}
@@ -149,30 +151,35 @@ load_shard_map(shardno_t shard_no, char* connstr)
shardno_t n_shards;
uint64 update_counter = pg_atomic_read_u64(&shard_map->update_counter);
/*
* There is race condition here between backendc and postmaster which can update shard map.
* We recheck update couner after copying connection string to check that configuration was not changed.
*/
while (shard_map_update_counter != update_counter)
if (shard_map_update_counter != update_counter)
{
/* Reset all connections */
/* Reset all connections if connection strings are changed */
for (shardno_t i = 0; i < max_attached_shard_no; i++)
{
if (page_servers[i].conn)
pageserver_disconnect(i);
}
max_attached_shard_no = 0;
}
/*
* There is race condition here between backendc and postmaster which can update shard map.
* We recheck update couner after copying connection string to check that configuration was not changed.
*/
do
{
shard_map_update_counter = update_counter;
n_shards = shard_map->n_shards;
if (shard_no >= n_shards)
elog(ERROR, "Shard %d is greater or equal than number of shards %d", shard_no, n_shards);
if (connstr)
strcpy(connstr, shard_map->shard_connstr[shard_no]);
strncpy(connstr, shard_map->shard_connstr[shard_no], MAX_PS_CONNSTR_LEN);
update_counter = pg_atomic_read_u64(&shard_map->update_counter);
}
while (update_counter != shard_map_update_counter);
return n_shards;
}
@@ -542,7 +549,7 @@ AssignPageserverConnstring(const char *newval, void *extra)
* Load shard map only at Postmaster.
* If old page server is not available, then backends can be blocked in attempts to reconnect to it and do not reload config in this loop
*/
if (MyProcPid == PostmasterPid)
if (shard_map != NULL && (MyProcPid == PostmasterPid || shard_map->n_shards == 0))
{
char const* shard_connstr = newval;
char const* sep;

1
pgxn/neon/pagestore_smgr.c
View File

@@ -964,7 +964,6 @@ page_server_request(void const *req)
do
{
while (!page_server->send(shard_no, (NeonRequest *) req) || !page_server->flush(shard_no));
MyPState->ring_flush = MyPState->ring_unused;
consume_prefetch_responses();
resp = page_server->receive(shard_no);
} while (resp == NULL);