PragmaTwice commented on code in PR #3295:
URL: https://github.com/apache/kvrocks/pull/3295#discussion_r2617801678
##########
src/cluster/cluster_failover.cc:
##########
@@ -0,0 +1,269 @@
+#include "cluster_failover.h"
+
+#include <unistd.h>
+
+#include "cluster/cluster.h"
+#include "common/io_util.h"
+#include "common/time_util.h"
+#include "logging.h"
+#include "server/redis_reply.h"
+#include "server/server.h"
+
+ClusterFailover::ClusterFailover(Server *srv) : srv_(srv) {
+ t_ = std::thread([this]() { loop(); });
+}
+
+ClusterFailover::~ClusterFailover() {
+ {
+ std::lock_guard<std::mutex> lock(mutex_);
+ stop_thread_ = true;
+ cv_.notify_all();
+ }
+ if (t_.joinable()) t_.join();
+}
+
+Status ClusterFailover::Run(std::string slave_node_id, int timeout_ms) {
+ std::lock_guard<std::mutex> lock(mutex_);
+ if (state_ != FailoverState::kNone && state_ != FailoverState::kFailed) {
+ return {Status::NotOK, "Failover is already in progress"};
+ }
+
+ slave_node_id_ = std::move(slave_node_id);
+ timeout_ms_ = timeout_ms;
+ state_ = FailoverState::kStarted;
+ failover_job_triggered_ = true;
+ cv_.notify_all();
+ return Status::OK();
+}
+
+void ClusterFailover::loop() {
+ while (true) {
+ std::unique_lock<std::mutex> lock(mutex_);
+ cv_.wait(lock, [this]() { return stop_thread_ || failover_job_triggered_;
});
+
+ if (stop_thread_) return;
+
+ if (failover_job_triggered_) {
+ failover_job_triggered_ = false;
+ lock.unlock();
+ runFailoverProcess();
+ }
+ }
+}
+
+void ClusterFailover::runFailoverProcess() {
+ auto ip_port = srv_->cluster->GetNodeIPPort(slave_node_id_);
+ if (!ip_port.IsOK()) {
+ error("[Failover] slave node not found in cluster {}", slave_node_id_);
+ abortFailover("Slave node not found in cluster");
+ return;
+ }
+ node_ip_port_ = ip_port.GetValue().first + ":" +
std::to_string(ip_port.GetValue().second);
+ node_ip_ = ip_port.GetValue().first;
+ node_port_ = ip_port.GetValue().second;
+ info("[Failover] slave node {} {} failover state: {}", slave_node_id_,
node_ip_port_, static_cast<int>(state_.load()));
+ state_ = FailoverState::kCheck;
+
+ auto s = checkSlaveStatus();
+ if (!s.IsOK()) {
+ abortFailover(s.Msg());
+ return;
+ }
+
+ s = checkSlaveLag();
+ if (!s.IsOK()) {
+ abortFailover("Slave lag check failed: " + s.Msg());
+ return;
+ }
+
+ info("[Failover] slave node {} {} check slave status success, enter pause
state", slave_node_id_, node_ip_port_);
+ start_time_ms_ = util::GetTimeStampMS();
+ // Enter Pause state (Stop writing)
+ state_ = FailoverState::kPause;
+ // Get current sequence
+ target_seq_ = srv_->storage->LatestSeqNumber();
+ info("[Failover] slave node {} {} target sequence {}", slave_node_id_,
node_ip_port_, target_seq_);
+
+ state_ = FailoverState::kSyncWait;
+ s = waitReplicationSync();
+ if (!s.IsOK()) {
+ abortFailover(s.Msg());
+ return;
+ }
+ info("[Failover] slave node {} {} wait replication sync success, enter
switch state, cost {} ms", slave_node_id_,
+ node_ip_port_, util::GetTimeStampMS() - start_time_ms_);
+
+ state_ = FailoverState::kSwitch;
+ s = sendTakeoverCmd();
+ if (!s.IsOK()) {
+ abortFailover(s.Msg());
+ return;
+ }
+
+ // Redirect slots
+ srv_->cluster->SetMySlotsMigrated(node_ip_port_);
+
+ state_ = FailoverState::kSuccess;
+ info("[Failover] success {} {}", slave_node_id_, node_ip_port_);
+}
+
+Status ClusterFailover::checkSlaveLag() {
+ auto start_offset_status = srv_->GetSlaveReplicationOffset(node_ip_port_);
+ if (!start_offset_status.IsOK()) {
+ return {Status::NotOK, "Failed to get slave offset: " +
start_offset_status.Msg()};
+ }
+ uint64_t start_offset = *start_offset_status;
+ int64_t start_sampling_ms = util::GetTimeStampMS();
+
+ // Wait 3s or half of timeout, but at least a bit to measure speed
+ int64_t wait_time = std::max(100, std::min(3000, timeout_ms_ / 2));
+ std::this_thread::sleep_for(std::chrono::milliseconds(wait_time));
+
+ auto end_offset_status = srv_->GetSlaveReplicationOffset(node_ip_port_);
+ if (!end_offset_status.IsOK()) {
+ return {Status::NotOK, "Failed to get slave offset: " +
end_offset_status.Msg()};
+ }
+ uint64_t end_offset = *end_offset_status;
+ int64_t end_sampling_ms = util::GetTimeStampMS();
+
+ double elapsed_sec = (end_sampling_ms - start_sampling_ms) / 1000.0;
+ if (elapsed_sec <= 0) elapsed_sec = 0.001;
+
+ uint64_t bytes = 0;
+ if (end_offset > start_offset) bytes = end_offset - start_offset;
+ double speed = bytes / elapsed_sec;
+
+ uint64_t master_seq = srv_->storage->LatestSeqNumber();
+ uint64_t lag = 0;
+ if (master_seq > end_offset) lag = master_seq - end_offset;
+
+ if (lag == 0) return Status::OK();
+
+ if (speed <= 0.1) { // Basically 0
+ return {Status::NotOK, fmt::format("Slave is not replicating (lag: {})",
lag)};
+ }
+
+ double required_sec = lag / speed;
+ int64_t required_ms = static_cast<int64_t>(required_sec * 1000);
+
+ int64_t elapsed_total = end_sampling_ms - start_sampling_ms;
+ int64_t remaining = timeout_ms_ - elapsed_total;
+
+ if (required_ms > remaining) {
+ return {Status::NotOK, fmt::format("Estimated catchup time {}ms >
remaining time {}ms (lag: {}, speed: {:.2f}/s)",
+ required_ms, remaining, lag, speed)};
+ }
+
+ info("[Failover] check: lag={}, speed={:.2f}/s, estimated_time={}ms,
remaining={}ms", lag, speed, required_ms,
+ remaining);
+ return Status::OK();
+}
+
+Status ClusterFailover::checkSlaveStatus() {
+ // We could try to connect, but GetSlaveReplicationOffset checks connection.
+ auto offset = srv_->GetSlaveReplicationOffset(node_ip_port_);
+ if (!offset.IsOK()) {
+ error("[Failover] slave node {} {} not connected or not syncing",
slave_node_id_, node_ip_port_);
+ return {Status::NotOK, "Slave not connected or not syncing"};
+ }
+ info("[Failover] slave node {} {} is connected and syncing offset {}",
slave_node_id_, node_ip_port_, offset.Msg());
Review Comment:
This is a false positive.
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