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Fix crash in expire when a snapshot is in flight. Caused by a perf optimization getting the expire map out of sync with the val

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This commit is contained in:
John Sully 2022-05-20 01:47:42 +00:00
parent 5dbf1f6bd6
commit ea4941a3e7
2 changed files with 8 additions and 2 deletions
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5
src/db.cpp
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@ -2669,6 +2669,11 @@ void redisDbPersistentData::prepOverwriteForSnapshot(char *key)
auto itr = m_pdbSnapshot->find_cached_threadsafe(key);
if (itr.key() != nullptr)
{
if (itr.val()->FExpires()) {
// Note: I'm sure we could handle this, but its too risky at the moment.
// There are known bugs doing this with expires
return;
}
sds keyNew = sdsdupshared(itr.key());
if (dictAdd(m_pdictTombstone, keyNew, (void*)dictHashKey(m_pdict, key)) != DICT_OK)
sdsfree(keyNew);

5
src/networking.cpp
View File

@ -2743,9 +2743,10 @@ void readQueryFromClient(connection *conn) {
parseClientCommandBuffer(c);
if (g_pserver->enable_async_commands && !serverTL->disable_async_commands && listLength(g_pserver->monitors) == 0 && (aeLockContention() || serverTL->rgdbSnapshot[c->db->id] || g_fTestMode)) {
// Frequent writers aren't good candidates for this optimization, they cause us to renew the snapshot too often
// so we exclude them unless the snapshot we need already exists
// so we exclude them unless the snapshot we need already exists.
// Note: In test mode we want to create snapshots as often as possibl to excercise them - we don't care about perf
bool fSnapshotExists = c->db->mvccLastSnapshot >= c->mvccCheckpoint;
bool fWriteTooRecent = (((getMvccTstamp() - c->mvccCheckpoint) >> MVCC_MS_SHIFT) < static_cast<uint64_t>(g_pserver->snapshot_slip)/2);
bool fWriteTooRecent = !g_fTestMode && (((getMvccTstamp() - c->mvccCheckpoint) >> MVCC_MS_SHIFT) < static_cast<uint64_t>(g_pserver->snapshot_slip)/2);
// The check below avoids running async commands if this is a frequent writer unless a snapshot is already there to service it
if (!fWriteTooRecent || fSnapshotExists) {