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[fix] set scn of election priority to MIN_SCN when access mode is not APPEND

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BinChenn
2023-07-20 06:48:01 +00:00
committed by ob-robot
parent 4a7f055b47
commit 0ad2b75b79
2 changed files with 22 additions and 22 deletions
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42
src/logservice/leader_coordinator/election_priority_impl/election_priority_v1.cpp
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@ -85,7 +85,7 @@ int PriorityV1::compare(const AbstractPriority &rhs, int &result, ObStringHolder
// ----------|------------------------------|-----------------
// APPEND | max_scn | max_replayed_scn
// ----------|------------------------------|-----------------
// RAW_WRITE | min(replayable_scn, max_scn) | max_replayed_scn
// RAW_WRITE | SCN::max_scn | SCN::max_scn
// ----------|------------------------------|-----------------
// OTHER | like RAW_WRITE
int PriorityV1::get_scn_(const share::ObLSID &ls_id, SCN &scn)
@ -97,12 +97,23 @@ int PriorityV1::get_scn_(const share::ObLSID &ls_id, SCN &scn)
palf::AccessMode access_mode = palf::AccessMode::INVALID_ACCESS_MODE;
ObLogService* log_service = MTL(ObLogService*);
common::ObRole role;
SCN replayable_scn, max_scn;
int64_t unused_pid = -1;
if (OB_ISNULL(log_service)) {
COORDINATOR_LOG_(ERROR, "ObLogService is nullptr");
} else if (CLICK_FAIL(log_service->open_palf(ls_id, palf_handle_guard))) {
COORDINATOR_LOG_(WARN, "open_palf failed");
} else if (CLICK_FAIL(palf_handle_guard.get_palf_handle()->get_access_mode(access_mode))) {
COORDINATOR_LOG_(WARN, "get_access_mode failed");
} else if (palf::AccessMode::APPEND != access_mode) {
// Note: set scn to max_scn when access mode is not APPEND.
// 1. A possible risk is when LS is switched from RAW_WRITE to APPEND, the leader
// may be APPEND and followers may be RAW_WRITE within a very short time window,
// the leader's scn (log sync max_scn) may be smaller than followers' scns (SCN::max_scn).
// To avoid the problem, if scn of a election priority is max_scn, we think the
// priority is equivalent to any priorities whose scn is any values.
// 2. Do not set scn to min_scn, if a follower do not replay any logs, its replayed_scn
// may be SCN::min_scn, and the leadership may be switched to the follower.
scn = SCN::max_scn();
} else if (CLICK_FAIL(palf_handle_guard.get_role(role, unused_pid))) {
COORDINATOR_LOG_(WARN, "get_role failed");
} else if (FOLLOWER == role) {
@ -110,28 +121,14 @@ int PriorityV1::get_scn_(const share::ObLSID &ls_id, SCN &scn)
COORDINATOR_LOG_(WARN, "failed to get_max_replayed_scn");
ret = OB_SUCCESS;
}
} else if (CLICK_FAIL(palf_handle_guard.get_palf_handle()->get_access_mode(access_mode))) {
COORDINATOR_LOG_(WARN, "get_access_mode failed");
} else if (palf::AccessMode::APPEND == access_mode) {
if (CLICK_FAIL(palf_handle_guard.get_max_scn(scn))) {
COORDINATOR_LOG_(WARN, "get_max_scn failed");
}
} else if (CLICK_FAIL(log_service->get_log_replay_service()->get_replayable_point(replayable_scn))) {
COORDINATOR_LOG_(WARN, "failed to get_replayable_point");
ret = OB_SUCCESS;
} else if (CLICK_FAIL(palf_handle_guard.get_max_scn(max_scn))) {
} else if (CLICK_FAIL(palf_handle_guard.get_max_scn(scn))) {
COORDINATOR_LOG_(WARN, "get_max_scn failed");
} else {
// For LEADER in RAW_WRITE mode, scn = min(replayable_scn, max_scn)
if (max_scn < replayable_scn) {
scn = max_scn;
} else {
scn = replayable_scn;
}
}
// scn may fallback because palf's role may be different with apply_service.
// So we need check it here to keep inc update semantic.
if (scn < scn_) {
// Note: scn is always max_scn when access mode is not APPEND, so we just
// keep its inc update semantic when cached scn_ is not SCN::max_scn
if (scn < scn_ && SCN::max_scn() != scn_) {
COORDINATOR_LOG_(TRACE, "new scn is smaller than current, no need update", K(role), K(access_mode), K(scn));
scn = scn_;
}
@ -339,7 +336,10 @@ int PriorityV1::compare_scn_(int &ret, const PriorityV1&rhs) const
{
int compare_result = 0;
if (OB_SUCC(ret)) {
if (scn_ == rhs.scn_) {
// If scn of a election priority is max_scn, we think the priority is
// equivalent to any priorities whose scn is any values.
// See detailed reason in PriorityV1::get_scn_
if (scn_ == rhs.scn_ || scn_.is_max() || rhs.scn_.is_max()) {
compare_result = 0;
} else if (scn_.is_valid() && rhs.scn_.is_valid()) {
if (std::max(scn_, rhs.scn_).convert_to_ts() - std::min(scn_, rhs.scn_).convert_to_ts() <= MAX_UNREPLAYED_LOG_TS_DIFF_THRESHOLD_US) {