void Balancer::run() {
Client::initThread("Balancer");
// This is the body of a BackgroundJob so if we throw here we're basically ending the balancer
// thread prematurely.
while (!inShutdown()) {
if (!_init()) {
log() << "will retry to initialize balancer in one minute";
sleepsecs(60);
continue;
}
break;
}
const int sleepTime = 10;
while (!inShutdown()) {
Timer balanceRoundTimer;
ActionLogType actionLog;
actionLog.setServer(getHostNameCached());
actionLog.setWhat("balancer.round");
try {
// ping has to be first so we keep things in the config server in sync
_ping();
BSONObj balancerResult;
// use fresh shard state
Shard::reloadShardInfo();
// refresh chunk size (even though another balancer might be active)
Chunk::refreshChunkSize();
auto balSettingsResult =
grid.catalogManager()->getGlobalSettings(SettingsType::BalancerDocKey);
const bool isBalSettingsAbsent =
balSettingsResult.getStatus() == ErrorCodes::NoMatchingDocument;
if (!balSettingsResult.isOK() && !isBalSettingsAbsent) {
warning() << balSettingsResult.getStatus();
return;
}
const SettingsType& balancerConfig =
isBalSettingsAbsent ? SettingsType{} :
balSettingsResult.getValue();
// now make sure we should even be running
if ((!isBalSettingsAbsent && !grid.shouldBalance(balancerConfig)) ||
MONGO_FAIL_POINT(skipBalanceRound)) {
LOG(1) << "skipping balancing round because balancing is disabled";
// Ping again so scripts can determine if we're active without waiting
_ping(true);
sleepsecs(sleepTime);
continue;
}
uassert(13258, "oids broken after resetting!", _checkOIDs());
{
auto scopedDistLock = grid.catalogManager()->getDistLockManager()->lock(
"balancer", "doing balance round");
if (!scopedDistLock.isOK()) {
LOG(1) << "skipping balancing round" << causedBy(scopedDistLock.getStatus());
// Ping again so scripts can determine if we're active without waiting
_ping(true);
sleepsecs(sleepTime); // no need to wake up soon
continue;
}
const bool waitForDelete =
(balancerConfig.isWaitForDeleteSet() ? balancerConfig.getWaitForDelete()
: false);
std::unique_ptr<WriteConcernOptions> writeConcern;
if (balancerConfig.isKeySet()) { // if balancer doc exists.
writeConcern = std::move(balancerConfig.getWriteConcern());
}
LOG(1) << "*** start balancing round. "
<< "waitForDelete: " << waitForDelete << ", secondaryThrottle: "
<< (writeConcern.get() ? writeConcern->toBSON().toString() : "default");
vector<shared_ptr<MigrateInfo>> candidateChunks;
_doBalanceRound(&candidateChunks);
if (candidateChunks.size() == 0) {
LOG(1) << "no need to move any chunk";
_balancedLastTime = 0;
} else {
_balancedLastTime =
_moveChunks(candidateChunks, writeConcern.get(), waitForDelete);
}
actionLog.setDetails(boost::none,
balanceRoundTimer.millis(),
static_cast<int>(candidateChunks.size()),
_balancedLastTime);
actionLog.setTime(jsTime());
grid.catalogManager()->logAction(actionLog);
LOG(1) << "*** end of balancing round";
}
// Ping again so scripts can determine if we're active without waiting
_ping(true);
sleepsecs(_balancedLastTime ? sleepTime / 10 : sleepTime);
} catch (std::exception& e) {
log() << "caught exception while doing balance: " << e.what();
// Just to match the opening statement if in log level 1
LOG(1) << "*** End of balancing round";
// This round failed, tell the world!
actionLog.setDetails(string(e.what()), balanceRoundTimer.millis(), 0, 0);
actionLog.setTime(jsTime());
grid.catalogManager()->logAction(actionLog);
// Sleep a fair amount before retrying because of the error
sleepsecs(sleepTime);
continue;
}
}
}
// balancer是background的job
void Balancer::run() {
// this is the body of a BackgroundJob so if we throw here we're basically ending the balancer
// thread prematurely
// 检查是否停机
while (!inShutdown()) {
// 检查是否初始化
if (!_init()) {
log() << "will retry to initialize balancer in one minute" << endl;
sleepsecs(60);
continue;
}
break;
}
int sleepTime = 10;
// getConnectioString and dist lock constructor does not throw, which is what we expect on while
// on the balancer thread
ConnectionString config = configServer.getConnectionString();
// 分布式锁，不知道要锁定什么
DistributedLock balanceLock(config, "balancer");
// 循环检查shutdown
while (!inShutdown()) {
Timer balanceRoundTimer;
ActionLogType actionLog;
actionLog.setServer(getHostNameCached());
actionLog.setWhat("balancer.round");
try {
ScopedDbConnection conn(config.toString(), 30);
// ping has to be first so we keep things in the config server in sync
_ping();
BSONObj balancerResult;
// use fresh shard state
Shard::reloadShardInfo();
// refresh chunk size (even though another balancer might be active)
Chunk::refreshChunkSize();
SettingsType balancerConfig;
string errMsg;
if (!grid.getBalancerSettings(&balancerConfig, &errMsg)) {
warning() << errMsg;
return;
}
// now make sure we should even be running
if ((balancerConfig.isKeySet() && // balancer config doc exists
!grid.shouldBalance(balancerConfig)) ||
MONGO_FAIL_POINT(skipBalanceRound)) {
LOG(1) << "skipping balancing round because balancing is disabled" << endl;
// Ping again so scripts can determine if we're active without waiting
_ping(true);
conn.done();
sleepsecs(sleepTime);
continue;
}
uassert(13258, "oids broken after resetting!", _checkOIDs());
{
dist_lock_try lk(&balanceLock, "doing balance round");
if (!lk.got()) {
LOG(1) << "skipping balancing round because another balancer is active" << endl;
// Ping again so scripts can determine if we're active without waiting
_ping(true);
conn.done();
sleepsecs(sleepTime); // no need to wake up soon
continue;
}
if (!isConfigServerConsistent()) {
conn.done();
warning() << "Skipping balancing round because data inconsistency"
<< " was detected amongst the config servers." << endl;
sleepsecs(sleepTime);
continue;
}
const bool waitForDelete =
(balancerConfig.isWaitForDeleteSet() ? balancerConfig.getWaitForDelete()
: false);
scoped_ptr<WriteConcernOptions> writeConcern;
if (balancerConfig.isKeySet()) { // if balancer doc exists.
StatusWith<WriteConcernOptions*> extractStatus =
balancerConfig.extractWriteConcern();
if (extractStatus.isOK()) {
writeConcern.reset(extractStatus.getValue());
} else {
warning() << extractStatus.toString();
}
}
LOG(1) << "*** start balancing round. "
<< "waitForDelete: " << waitForDelete << ", secondaryThrottle: "
<< (writeConcern.get() ? writeConcern->toBSON().toString() : "default")
<< endl;
vector<CandidateChunkPtr> candidateChunks;
_doBalanceRound(conn.conn(), &candidateChunks);
if (candidateChunks.size() == 0) {
LOG(1) << "no need to move any chunk" << endl;
_balancedLastTime = 0;
} else {
_balancedLastTime =
_moveChunks(&candidateChunks, writeConcern.get(), waitForDelete);
}
actionLog.setDetails(_buildDetails(false,
balanceRoundTimer.millis(),
static_cast<int>(candidateChunks.size()),
_balancedLastTime,
""));
_reportRound(actionLog);
LOG(1) << "*** end of balancing round" << endl;
}
// Ping again so scripts can determine if we're active without waiting
_ping(true);
conn.done();
sleepsecs(_balancedLastTime ? sleepTime / 10 : sleepTime);
} catch (std::exception& e) {
log() << "caught exception while doing balance: " << e.what() << endl;
// Just to match the opening statement if in log level 1
LOG(1) << "*** End of balancing round" << endl;
// This round failed, tell the world!
actionLog.setDetails(_buildDetails(true, balanceRoundTimer.millis(), 0, 0, e.what()));
_reportRound(actionLog);
sleepsecs(sleepTime); // sleep a fair amount b/c of error
continue;
}
}
}