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|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kNetwork
#include "mongo/platform/basic.h"
#include "mongo/client/replica_set_monitor.h"
#include <algorithm>
#include <limits>
#include <random>
#include "mongo/bson/simple_bsonelement_comparator.h"
#include "mongo/client/connpool.h"
#include "mongo/client/global_conn_pool.h"
#include "mongo/client/read_preference.h"
#include "mongo/client/replica_set_monitor_internal.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/repl/bson_extract_optime.h"
#include "mongo/db/server_options.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/background.h"
#include "mongo/util/debug_util.h"
#include "mongo/util/exit.h"
#include "mongo/util/fail_point_service.h"
#include "mongo/util/log.h"
#include "mongo/util/string_map.h"
#include "mongo/util/timer.h"
namespace mongo {
using std::shared_ptr;
using std::numeric_limits;
using std::set;
using std::string;
using std::vector;
// Failpoint for changing the default refresh period
MONGO_FAIL_POINT_DEFINE(modifyReplicaSetMonitorDefaultRefreshPeriod);
namespace {
// Pull nested types to top-level scope
typedef ReplicaSetMonitor::IsMasterReply IsMasterReply;
typedef ReplicaSetMonitor::ScanState ScanState;
typedef ReplicaSetMonitor::ScanStatePtr ScanStatePtr;
typedef ReplicaSetMonitor::SetState SetState;
typedef ReplicaSetMonitor::SetStatePtr SetStatePtr;
typedef ReplicaSetMonitor::Refresher Refresher;
typedef ScanState::UnconfirmedReplies UnconfirmedReplies;
typedef SetState::Node Node;
typedef SetState::Nodes Nodes;
using executor::TaskExecutor;
using CallbackArgs = TaskExecutor::CallbackArgs;
using CallbackHandle = TaskExecutor::CallbackHandle;
const double socketTimeoutSecs = 5;
// Intentionally chosen to compare worse than all known latencies.
const int64_t unknownLatency = numeric_limits<int64_t>::max();
const ReadPreferenceSetting kPrimaryOnlyReadPreference(ReadPreference::PrimaryOnly, TagSet());
const Milliseconds kExpeditedRefreshPeriod(500);
AtomicWord<bool> areRefreshRetriesDisabledForTest{false}; // Only true in tests.
//
// Helpers for stl algorithms
//
bool isMaster(const Node& node) {
return node.isMaster;
}
bool opTimeGreater(const Node* lhs, const Node* rhs) {
return lhs->opTime > rhs->opTime;
}
bool compareLatencies(const Node* lhs, const Node* rhs) {
// NOTE: this automatically compares Node::unknownLatency worse than all others.
return lhs->latencyMicros < rhs->latencyMicros;
}
bool hostsEqual(const Node& lhs, const HostAndPort& rhs) {
return lhs.host == rhs;
}
// Allows comparing two Nodes, or a HostAndPort and a Node.
// NOTE: the two HostAndPort overload is only needed to support extra checks in some STL
// implementations. For simplicity, no comparator should be used with collections of just
// HostAndPort.
struct CompareHosts {
bool operator()(const Node& lhs, const Node& rhs) {
return lhs.host < rhs.host;
}
bool operator()(const Node& lhs, const HostAndPort& rhs) {
return lhs.host < rhs;
}
bool operator()(const HostAndPort& lhs, const Node& rhs) {
return lhs < rhs.host;
}
bool operator()(const HostAndPort& lhs, const HostAndPort& rhs) {
return lhs < rhs;
}
} compareHosts; // like an overloaded function, but able to pass to stl algorithms
// The following structs should be treated as functions returning a UnaryPredicate.
// Usage example: std::find_if(nodes.begin(), nodes.end(), HostIs(someHost));
// They all hold their constructor argument by reference.
struct HostIs {
explicit HostIs(const HostAndPort& host) : _host(host) {}
bool operator()(const HostAndPort& host) {
return host == _host;
}
bool operator()(const Node& node) {
return node.host == _host;
}
const HostAndPort& _host;
};
struct HostNotIn {
explicit HostNotIn(const std::set<HostAndPort>& hosts) : _hosts(hosts) {}
bool operator()(const HostAndPort& host) {
return !_hosts.count(host);
}
bool operator()(const Node& node) {
return !_hosts.count(node.host);
}
const std::set<HostAndPort>& _hosts;
};
int32_t pingTimeMillis(const Node& node) {
auto latencyMillis = node.latencyMicros / 1000;
if (latencyMillis > numeric_limits<int32_t>::max()) {
// In particular, Node::unknownLatency does not fit in an int32.
return numeric_limits<int32_t>::max();
}
return latencyMillis;
}
/**
* Replica set refresh period on the task executor.
*/
const Seconds kDefaultRefreshPeriod(30);
} // namespace
// If we cannot find a host after 15 seconds of refreshing, give up
const Seconds ReplicaSetMonitor::kDefaultFindHostTimeout(15);
// Defaults to random selection as required by the spec
bool ReplicaSetMonitor::useDeterministicHostSelection = false;
Seconds ReplicaSetMonitor::getDefaultRefreshPeriod() {
MONGO_FAIL_POINT_BLOCK_IF(modifyReplicaSetMonitorDefaultRefreshPeriod,
data,
[&](const BSONObj& data) { return data.hasField("period"); }) {
return Seconds{data.getData().getIntField("period")};
}
return kDefaultRefreshPeriod;
}
ReplicaSetMonitor::ReplicaSetMonitor(const SetStatePtr& initialState) : _state(initialState) {}
ReplicaSetMonitor::ReplicaSetMonitor(const MongoURI& uri)
: ReplicaSetMonitor(std::make_shared<SetState>(
uri, &globalRSMonitorManager.getNotifier(), globalRSMonitorManager.getExecutor())) {}
void ReplicaSetMonitor::init() {
if (areRefreshRetriesDisabledForTest.load()) {
// This is for MockReplicaSet. Those tests want to control when scanning happens.
warning() << "*** Not starting background refresh because refresh retries are disabled.";
return;
}
_state->init();
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
_scheduleRefresh(_state->now(), lk);
}
ReplicaSetMonitor::~ReplicaSetMonitor() {
_state->drop();
}
void ReplicaSetMonitor::_scheduleRefresh(Date_t when, WithLock) {
// Reschedule the refresh
invariant(_state->executor);
if (_isRemovedFromManager.load()) { // already removed so no need to refresh
LOG(1) << "Stopping refresh for replica set " << getName() << " because its removed";
return;
}
std::weak_ptr<ReplicaSetMonitor> that(shared_from_this());
auto status = _state->executor->scheduleWorkAt(when, [that](const CallbackArgs& cbArgs) {
if (!cbArgs.status.isOK())
return;
if (auto ptr = that.lock()) {
ptr->_doScheduledRefresh(cbArgs.myHandle);
}
});
if (status.getStatus() == ErrorCodes::ShutdownInProgress) {
LOG(1) << "Cant schedule refresh for " << getName() << ". Executor shutdown in progress";
return;
}
if (!status.isOK()) {
severe() << "Can't continue refresh for replica set " << getName() << " due to "
<< redact(status.getStatus());
fassertFailed(40140);
}
_refresherHandle = status.getValue();
}
void ReplicaSetMonitor::_doScheduledRefresh(const CallbackHandle& currentHandle) {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
if (currentHandle != _refresherHandle)
return; // We've been replaced!
Refresher::ensureScanInProgress(_state, lk);
Milliseconds period = _state->refreshPeriod;
if (_state->isExpedited) {
if (_state->waiters.empty()) {
// No current waiters so we can stop the expedited scanning.
_state->isExpedited = false;
} else {
period = std::min(period, kExpeditedRefreshPeriod);
}
}
// And now we set up the next one
_scheduleRefresh(_state->now() + period, lk);
}
SemiFuture<HostAndPort> ReplicaSetMonitor::getHostOrRefresh(const ReadPreferenceSetting& criteria,
Milliseconds maxWait) {
return _getHostsOrRefresh(criteria, maxWait)
.then([](const auto& hosts) {
invariant(hosts.size());
return hosts[0];
})
.semi();
}
SemiFuture<std::vector<HostAndPort>> ReplicaSetMonitor::getHostsOrRefresh(
const ReadPreferenceSetting& criteria, Milliseconds maxWait) {
return _getHostsOrRefresh(criteria, maxWait).semi();
}
Future<std::vector<HostAndPort>> ReplicaSetMonitor::_getHostsOrRefresh(
const ReadPreferenceSetting& criteria, Milliseconds maxWait) {
// If we're in shutdown, don't bother
if (globalInShutdownDeprecated()) {
return Status(ErrorCodes::ShutdownInProgress, "Server is shutting down"_sd);
}
if (_isRemovedFromManager.load()) {
return Status(ErrorCodes::ReplicaSetMonitorRemoved,
str::stream() << "ReplicaSetMonitor for set " << getName() << " is removed");
}
// Fast path, for the failure-free case
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
auto out = _state->getMatchingHosts(criteria);
if (!out.empty())
return {std::move(out)};
// Fail early without doing any more work if the timeout has already expired.
if (maxWait <= Milliseconds(0))
return _state->makeUnsatisfedReadPrefError(criteria);
// TODO look into putting all PrimaryOnly waiters on a single SharedPromise. The tricky part is
// dealing with maxWait.
auto pf = makePromiseFuture<decltype(out)>();
_state->waiters.emplace_back(
SetState::Waiter{_state->now() + maxWait, criteria, std::move(pf.promise)});
// This must go after we set up the wait state to correctly handle unittests using
// MockReplicaSet.
Refresher::ensureScanInProgress(_state, lk);
if (!_state->isExpedited && _refresherHandle &&
!MONGO_FAIL_POINT(modifyReplicaSetMonitorDefaultRefreshPeriod)) {
// We are the first waiter, switch to expedited scanning.
_state->isExpedited = true;
_state->executor->cancel(_refresherHandle);
_refresherHandle = {};
_scheduleRefresh(_state->now() + kExpeditedRefreshPeriod, lk);
}
return std::move(pf.future);
}
HostAndPort ReplicaSetMonitor::getMasterOrUassert() {
return getHostOrRefresh(kPrimaryOnlyReadPreference).get();
}
void ReplicaSetMonitor::failedHost(const HostAndPort& host, const Status& status) {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
Node* node = _state->findNode(host);
if (node)
node->markFailed(status);
DEV _state->checkInvariants();
}
bool ReplicaSetMonitor::isPrimary(const HostAndPort& host) const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
Node* node = _state->findNode(host);
return node ? node->isMaster : false;
}
bool ReplicaSetMonitor::isHostUp(const HostAndPort& host) const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
Node* node = _state->findNode(host);
return node ? node->isUp : false;
}
int ReplicaSetMonitor::getMinWireVersion() const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
int minVersion = 0;
for (const auto& host : _state->nodes) {
if (host.isUp) {
minVersion = std::max(minVersion, host.minWireVersion);
}
}
return minVersion;
}
int ReplicaSetMonitor::getMaxWireVersion() const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
int maxVersion = std::numeric_limits<int>::max();
for (const auto& host : _state->nodes) {
if (host.isUp) {
maxVersion = std::min(maxVersion, host.maxWireVersion);
}
}
return maxVersion;
}
std::string ReplicaSetMonitor::getName() const {
// name is const so don't need to lock
return _state->name;
}
std::string ReplicaSetMonitor::getServerAddress() const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
// We return our setUri until first confirmation
return _state->seedConnStr.isValid() ? _state->seedConnStr.toString()
: _state->setUri.connectionString().toString();
}
const MongoURI& ReplicaSetMonitor::getOriginalUri() const {
// setUri is const so no need to lock.
return _state->setUri;
}
bool ReplicaSetMonitor::contains(const HostAndPort& host) const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
return _state->seedNodes.count(host);
}
shared_ptr<ReplicaSetMonitor> ReplicaSetMonitor::createIfNeeded(const string& name,
const set<HostAndPort>& servers) {
return globalRSMonitorManager.getOrCreateMonitor(
ConnectionString::forReplicaSet(name, vector<HostAndPort>(servers.begin(), servers.end())));
}
shared_ptr<ReplicaSetMonitor> ReplicaSetMonitor::createIfNeeded(const MongoURI& uri) {
return globalRSMonitorManager.getOrCreateMonitor(uri);
}
shared_ptr<ReplicaSetMonitor> ReplicaSetMonitor::get(const std::string& name) {
return globalRSMonitorManager.getMonitor(name);
}
void ReplicaSetMonitor::remove(const string& name) {
globalRSMonitorManager.removeMonitor(name);
// Kill all pooled ReplicaSetConnections for this set. They will not function correctly
// after we kill the ReplicaSetMonitor.
globalConnPool.removeHost(name);
}
ReplicaSetChangeNotifier& ReplicaSetMonitor::getNotifier() {
return globalRSMonitorManager.getNotifier();
}
// TODO move to correct order with non-statics before pushing
void ReplicaSetMonitor::appendInfo(BSONObjBuilder& bsonObjBuilder, bool forFTDC) const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
BSONObjBuilder monitorInfo(bsonObjBuilder.subobjStart(getName()));
if (forFTDC) {
for (size_t i = 0; i < _state->nodes.size(); i++) {
const Node& node = _state->nodes[i];
monitorInfo.appendNumber(node.host.toString(), pingTimeMillis(node));
}
return;
}
// NOTE: the format here must be consistent for backwards compatibility
BSONArrayBuilder hosts(monitorInfo.subarrayStart("hosts"));
for (size_t i = 0; i < _state->nodes.size(); i++) {
const Node& node = _state->nodes[i];
BSONObjBuilder builder;
builder.append("addr", node.host.toString());
builder.append("ok", node.isUp);
builder.append("ismaster", node.isMaster); // intentionally not camelCase
builder.append("hidden", false); // we don't keep hidden nodes in the set
builder.append("secondary", node.isUp && !node.isMaster);
builder.append("pingTimeMillis", pingTimeMillis(node));
if (!node.tags.isEmpty()) {
builder.append("tags", node.tags);
}
hosts.append(builder.obj());
}
}
void ReplicaSetMonitor::shutdown() {
globalRSMonitorManager.shutdown();
}
void ReplicaSetMonitor::cleanup() {
globalRSMonitorManager.removeAllMonitors();
}
void ReplicaSetMonitor::disableRefreshRetries_forTest() {
areRefreshRetriesDisabledForTest.store(true);
}
bool ReplicaSetMonitor::isKnownToHaveGoodPrimary() const {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
for (const auto& node : _state->nodes) {
if (node.isMaster) {
return true;
}
}
return false;
}
void ReplicaSetMonitor::markAsRemoved() {
_isRemovedFromManager.store(true);
}
void ReplicaSetMonitor::runScanForMockReplicaSet() {
stdx::lock_guard<stdx::mutex> lk(_state->mutex);
Refresher::ensureScanInProgress(_state, lk);
// This function should only be called from tests using MockReplicaSet and they should use the
// synchronous path to complete before returning.
invariant(_state->currentScan == nullptr);
}
void Refresher::ensureScanInProgress(const SetStatePtr& set, WithLock lk) {
Refresher(set).scheduleNetworkRequests(lk);
}
Refresher::Refresher(const SetStatePtr& setState) : _set(setState), _scan(setState->currentScan) {
if (_scan) {
_scan->retryAllTriedHosts(_set->rand);
return; // participate in in-progress scan
}
LOG(2) << "Starting new refresh of replica set " << _set->name;
_scan = startNewScan(_set.get());
_set->currentScan = _scan;
}
void Refresher::scheduleNetworkRequests(WithLock withLock) {
while (true) {
auto ns = getNextStep();
if (ns.step != Refresher::NextStep::CONTACT_HOST)
break;
scheduleIsMaster(ns.host, withLock);
}
DEV _set->checkInvariants();
}
void Refresher::scheduleIsMaster(const HostAndPort& host, WithLock withLock) {
if (_set->isMocked) {
// MockReplicaSet only works with DBClient-style access since it injects itself into the
// ScopedDbConnection pool connection creation.
try {
ScopedDbConnection conn(ConnectionString(host), socketTimeoutSecs);
auto timer = Timer();
auto reply = BSONObj();
bool ignoredOutParam = false;
conn->isMaster(ignoredOutParam, &reply);
conn.done(); // return to pool on success.
receivedIsMaster(host, timer.micros(), reply);
} catch (DBException& ex) {
failedHost(host, ex.toStatus());
}
return;
}
auto request = executor::RemoteCommandRequest(host,
"admin",
BSON("isMaster" << 1),
nullptr,
Milliseconds(int64_t(socketTimeoutSecs * 1000)));
request.sslMode = _set->setUri.getSSLMode();
auto status =
_set->executor
->scheduleRemoteCommand(
std::move(request),
[ copy = *this, host, timer = Timer() ](
const executor::TaskExecutor::RemoteCommandCallbackArgs& result) mutable {
stdx::lock_guard<stdx::mutex> lk(copy._set->mutex);
// Ignore the reply and return if we are no longer the current scan. This might
// happen if it was decided that the host we were contacting isn't part of the
// set.
if (copy._scan != copy._set->currentScan)
return;
if (result.response.isOK()) {
// Not using result.response.elapsedMillis because higher precision is
// useful for computing the rolling average.
copy.receivedIsMaster(host, timer.micros(), result.response.data);
} else {
copy.failedHost(host, result.response.status);
}
// This reply may have discovered new hosts to contact so we need to schedule
// them.
copy.scheduleNetworkRequests(lk);
})
.getStatus();
if (!status.isOK()) {
failedHost(host, status);
// This is only called from scheduleNetworkRequests() which will still be looping, so we
// don't need to call it here after updating the state.
}
}
Refresher::NextStep Refresher::getNextStep() {
// No longer the current scan
if (_scan != _set->currentScan) {
return NextStep(NextStep::DONE);
}
// Wait for all dispatched hosts to return before trying any fallback hosts.
if (_scan->hostsToScan.empty() && !_scan->waitingFor.empty()) {
return NextStep(NextStep::WAIT);
}
// If we haven't yet found a master, try contacting unconfirmed hosts
if (_scan->hostsToScan.empty() && !_scan->foundUpMaster) {
_scan->enqueAllUntriedHosts(_scan->possibleNodes, _set->rand);
_scan->possibleNodes.clear();
}
if (_scan->hostsToScan.empty()) {
// We've tried all hosts we can, so nothing more to do in this round.
if (!_scan->foundUpMaster) {
warning() << "Unable to reach primary for set " << _set->name;
// Since we've talked to everyone we could but still didn't find a primary, we
// do the best we can, and assume all unconfirmedReplies are actually from nodes
// in the set (we've already confirmed that they think they are). This is
// important since it allows us to bootstrap to a usable state even if we are
// unable to talk to a master while starting up. As soon as we are able to
// contact a master, we will remove any nodes that it doesn't think are part of
// the set, undoing the damage we cause here.
// NOTE: we don't modify seedNodes or notify about set membership change in this
// case since it hasn't been confirmed by a master.
for (UnconfirmedReplies::iterator it = _scan->unconfirmedReplies.begin();
it != _scan->unconfirmedReplies.end();
++it) {
_set->findOrCreateNode(it->first)->update(it->second);
}
auto connStr = _set->possibleConnectionString();
if (connStr != _set->workingConnStr) {
_set->workingConnStr = std::move(connStr);
_set->notifier->onPossibleSet(_set->workingConnStr);
}
// If at some point we care about lacking a primary, on it here
_set->lastSeenMaster = {};
}
if (_scan->foundAnyUpNodes) {
_set->consecutiveFailedScans = 0;
} else {
auto nScans = _set->consecutiveFailedScans++;
if (nScans <= 10 || nScans % 10 == 0) {
log() << "Cannot reach any nodes for set " << _set->name
<< ". Please check network connectivity and the status of the set. "
<< "This has happened for " << _set->consecutiveFailedScans
<< " checks in a row.";
}
}
// Makes sure all other Refreshers in this round return DONE
_set->currentScan.reset();
_set->notify(/*finishedScan*/ true);
LOG(1) << "Refreshing replica set " << _set->name << " took " << _scan->timer.millis()
<< "ms";
return NextStep(NextStep::DONE);
}
// Pop and return the next hostToScan.
HostAndPort host = _scan->hostsToScan.front();
_scan->hostsToScan.pop_front();
_scan->waitingFor.insert(host);
_scan->triedHosts.insert(host);
return NextStep(NextStep::CONTACT_HOST, host);
}
void Refresher::receivedIsMaster(const HostAndPort& from,
int64_t latencyMicros,
const BSONObj& replyObj) {
_scan->waitingFor.erase(from);
const IsMasterReply reply(from, latencyMicros, replyObj);
// Handle various failure cases
if (!reply.ok) {
failedHost(from, {ErrorCodes::CommandFailed, "Failed to execute 'ismaster' command"});
return;
}
if (reply.setName != _set->name) {
if (reply.raw["isreplicaset"].trueValue()) {
// The reply came from a node in the state referred to as RSGhost in the SDAM
// spec. RSGhost corresponds to either REMOVED or STARTUP member states. In any event,
// if a reply from a ghost offers a list of possible other members of the replica set,
// and if this refresher has yet to find the replica set master, we add hosts listed in
// the reply to the list of possible replica set members.
if (!_scan->foundUpMaster) {
_scan->possibleNodes.insert(reply.normalHosts.begin(), reply.normalHosts.end());
}
} else {
error() << "replset name mismatch: expected \"" << _set->name << "\", "
<< "but remote node " << from << " has replset name \"" << reply.setName << "\""
<< ", ismaster: " << replyObj;
}
failedHost(from,
{ErrorCodes::InconsistentReplicaSetNames,
str::stream() << "Target replica set name " << reply.setName
<< " does not match the monitored set name "
<< _set->name});
return;
}
if (reply.isMaster) {
Status status = receivedIsMasterFromMaster(from, reply);
if (!status.isOK()) {
failedHost(from, status);
return;
}
}
if (_scan->foundUpMaster) {
// We only update a Node if a master has confirmed it is in the set.
_set->updateNodeIfInNodes(reply);
_set->notify(/*finishedScan*/ false);
} else {
// Populate possibleNodes.
_scan->possibleNodes.insert(reply.normalHosts.begin(), reply.normalHosts.end());
_scan->unconfirmedReplies[from] = reply;
}
// _set->nodes may still not have any nodes with isUp==true, but we have at least found a
// connectible host that is that claims to be in the set.
_scan->foundAnyUpNodes = true;
DEV _set->checkInvariants();
}
void Refresher::failedHost(const HostAndPort& host, const Status& status) {
_scan->waitingFor.erase(host);
Node* node = _set->findNode(host);
if (node)
node->markFailed(status);
}
ScanStatePtr Refresher::startNewScan(const SetState* set) {
const ScanStatePtr scan = std::make_shared<ScanState>();
// The heuristics we use in deciding the order to contact hosts are designed to find a
// master as quickly as possible. This is because we can't use any hosts we find until
// we either get the latest set of members from a master or talk to all possible hosts
// without finding a master.
// TODO It might make sense to check down nodes first if the last seen master is still
// marked as up.
int upNodes = 0;
for (Nodes::const_iterator it(set->nodes.begin()), end(set->nodes.end()); it != end; ++it) {
if (it->isUp) {
// scan the nodes we think are up first
scan->hostsToScan.push_front(it->host);
upNodes++;
} else {
scan->hostsToScan.push_back(it->host);
}
}
// shuffle the queue, but keep "up" nodes at the front
std::shuffle(scan->hostsToScan.begin(), scan->hostsToScan.begin() + upNodes, set->rand.urbg());
std::shuffle(scan->hostsToScan.begin() + upNodes, scan->hostsToScan.end(), set->rand.urbg());
if (!set->lastSeenMaster.empty()) {
// move lastSeenMaster to front of queue
std::stable_partition(
scan->hostsToScan.begin(), scan->hostsToScan.end(), HostIs(set->lastSeenMaster));
}
return scan;
}
Status Refresher::receivedIsMasterFromMaster(const HostAndPort& from, const IsMasterReply& reply) {
invariant(reply.isMaster);
// Reject if config version is older. This is for backwards compatibility with nodes in pv0
// since they don't have the same ordering with pv1 electionId.
if (reply.configVersion < _set->configVersion) {
return {ErrorCodes::NotMaster,
str::stream() << "Node " << from
<< " believes it is primary, but its config version "
<< reply.configVersion
<< " is older than the most recent config version "
<< _set->configVersion};
}
if (reply.electionId.isSet()) {
// ElectionIds are only comparable if they are of the same protocol version. However, since
// isMaster has no protocol version field, we use the configVersion instead. This works
// because configVersion needs to be incremented whenever the protocol version is changed.
if (reply.configVersion == _set->configVersion && _set->maxElectionId.isSet() &&
_set->maxElectionId.compare(reply.electionId) > 0) {
return {ErrorCodes::NotMaster,
str::stream() << "Node " << from
<< " believes it is primary, but its election id "
<< reply.electionId
<< " is older than the most recent election id "
<< _set->maxElectionId};
}
_set->maxElectionId = reply.electionId;
}
_set->configVersion = reply.configVersion;
// Mark all nodes as not master. We will mark ourself as master before releasing the lock.
// NOTE: we use a "last-wins" policy if multiple hosts claim to be master.
for (size_t i = 0; i < _set->nodes.size(); i++) {
_set->nodes[i].isMaster = false;
}
// Check if the master agrees with our current list of nodes.
// REMINDER: both _set->nodes and reply.normalHosts are sorted.
if (_set->nodes.size() != reply.normalHosts.size() ||
!std::equal(
_set->nodes.begin(), _set->nodes.end(), reply.normalHosts.begin(), hostsEqual)) {
LOG(2) << "Adjusting nodes in our view of replica set " << _set->name
<< " based on master reply: " << redact(reply.raw);
// remove non-members from _set->nodes
_set->nodes.erase(
std::remove_if(_set->nodes.begin(), _set->nodes.end(), HostNotIn(reply.normalHosts)),
_set->nodes.end());
// add new members to _set->nodes
for (std::set<HostAndPort>::const_iterator it = reply.normalHosts.begin();
it != reply.normalHosts.end();
++it) {
_set->findOrCreateNode(*it);
}
// replace hostToScan queue with untried normal hosts. can both add and remove
// hosts from the queue.
_scan->hostsToScan.clear();
_scan->enqueAllUntriedHosts(reply.normalHosts, _set->rand);
if (!_scan->waitingFor.empty()) {
// make sure we don't wait for any hosts that aren't considered members
std::set<HostAndPort> newWaitingFor;
std::set_intersection(reply.normalHosts.begin(),
reply.normalHosts.end(),
_scan->waitingFor.begin(),
_scan->waitingFor.end(),
std::inserter(newWaitingFor, newWaitingFor.end()));
_scan->waitingFor.swap(newWaitingFor);
}
}
bool changedHosts = reply.normalHosts != _set->seedNodes;
bool changedPrimary = reply.host != _set->lastSeenMaster;
if (changedHosts || changedPrimary) {
++_set->seedGen;
_set->seedNodes = reply.normalHosts;
_set->seedConnStr = _set->confirmedConnectionString();
// LogLevel can be pretty low, since replica set reconfiguration should be pretty rare
// and we want to record our changes
log() << "Confirmed replica set for " << _set->name << " is " << _set->seedConnStr;
_set->notifier->onConfirmedSet(_set->seedConnStr, reply.host);
}
// Update our working string
_set->workingConnStr = _set->seedConnStr;
// Update other nodes's information based on replies we've already seen
for (UnconfirmedReplies::iterator it = _scan->unconfirmedReplies.begin();
it != _scan->unconfirmedReplies.end();
++it) {
// this ignores replies from hosts not in _set->nodes (as modified above)
_set->updateNodeIfInNodes(it->second);
}
_scan->unconfirmedReplies.clear();
_scan->foundUpMaster = true;
_set->lastSeenMaster = reply.host;
return Status::OK();
}
void IsMasterReply::parse(const BSONObj& obj) {
try {
raw = obj.getOwned(); // don't use obj again after this line
ok = raw["ok"].trueValue();
if (!ok)
return;
setName = raw["setName"].str();
hidden = raw["hidden"].trueValue();
secondary = raw["secondary"].trueValue();
minWireVersion = raw["minWireVersion"].numberInt();
maxWireVersion = raw["maxWireVersion"].numberInt();
// hidden nodes can't be master, even if they claim to be.
isMaster = !hidden && raw["ismaster"].trueValue();
if (isMaster && raw.hasField("electionId")) {
electionId = raw["electionId"].OID();
}
configVersion = raw["setVersion"].numberInt();
const string primaryString = raw["primary"].str();
primary = primaryString.empty() ? HostAndPort() : HostAndPort(primaryString);
// both hosts and passives, but not arbiters, are considered "normal hosts"
normalHosts.clear();
BSONForEach(host, raw.getObjectField("hosts")) {
normalHosts.insert(HostAndPort(host.String()));
}
BSONForEach(host, raw.getObjectField("passives")) {
normalHosts.insert(HostAndPort(host.String()));
}
tags = raw.getObjectField("tags");
BSONObj lastWriteField = raw.getObjectField("lastWrite");
if (!lastWriteField.isEmpty()) {
if (auto lastWrite = lastWriteField["lastWriteDate"]) {
lastWriteDate = lastWrite.date();
}
uassertStatusOK(bsonExtractOpTimeField(lastWriteField, "opTime", &opTime));
}
} catch (const std::exception& e) {
ok = false;
log() << "exception while parsing isMaster reply: " << e.what() << " " << obj;
}
}
Node::Node(const HostAndPort& host) : host(host), latencyMicros(unknownLatency) {}
void Node::markFailed(const Status& status) {
if (isUp) {
log() << "Marking host " << host << " as failed" << causedBy(redact(status));
isUp = false;
}
isMaster = false;
}
bool Node::matches(const ReadPreference pref) const {
if (!isUp)
return false;
if (pref == ReadPreference::PrimaryOnly) {
return isMaster;
}
if (pref == ReadPreference::SecondaryOnly) {
if (isMaster)
return false;
}
return true;
}
bool Node::matches(const BSONObj& tag) const {
BSONForEach(tagCriteria, tag) {
if (SimpleBSONElementComparator::kInstance.evaluate(
this->tags[tagCriteria.fieldNameStringData()] != tagCriteria)) {
return false;
}
}
return true;
}
void Node::update(const IsMasterReply& reply) {
invariant(host == reply.host);
invariant(reply.ok);
LOG(3) << "Updating host " << host << " based on ismaster reply: " << reply.raw;
// Nodes that are hidden or neither master or secondary are considered down since we can't
// send any operations to them.
isUp = !reply.hidden && (reply.isMaster || reply.secondary);
isMaster = reply.isMaster;
minWireVersion = reply.minWireVersion;
maxWireVersion = reply.maxWireVersion;
// save a copy if unchanged
if (!tags.binaryEqual(reply.tags))
tags = reply.tags.getOwned();
if (reply.latencyMicros >= 0) { // TODO upper bound?
if (latencyMicros == unknownLatency) {
latencyMicros = reply.latencyMicros;
} else {
// update latency with smoothed moving average (1/4th the delta)
latencyMicros += (reply.latencyMicros - latencyMicros) / 4;
}
}
LOG(3) << "Updating " << host << " lastWriteDate to " << reply.lastWriteDate;
lastWriteDate = reply.lastWriteDate;
LOG(3) << "Updating " << host << " opTime to " << reply.opTime;
opTime = reply.opTime;
lastWriteDateUpdateTime = Date_t::now();
}
SetState::SetState(const MongoURI& uri,
ReplicaSetChangeNotifier* notifier,
executor::TaskExecutor* executor)
: setUri(std::move(uri)),
name(setUri.getSetName()),
notifier(notifier),
executor(executor),
seedNodes(setUri.getServers().begin(), setUri.getServers().end()),
latencyThresholdMicros(serverGlobalParams.defaultLocalThresholdMillis * int64_t(1000)),
rand(std::random_device()()),
refreshPeriod(getDefaultRefreshPeriod()) {
uassert(13642, "Replica set seed list can't be empty", !seedNodes.empty());
if (name.empty())
warning() << "Replica set name empty, first node: " << *(seedNodes.begin());
// This adds the seed hosts to nodes, but they aren't usable for anything except seeding a
// scan until we start a scan and either find a master or contact all hosts without finding
// one.
// WARNING: if seedNodes is ever changed to not imply sorted iteration, you will need to
// sort nodes after this loop.
for (auto&& addr : seedNodes) {
nodes.push_back(Node(addr));
if (addr.host()[0] == '$') {
invariant(isMocked || &addr == &*seedNodes.begin()); // Can't mix and match.
isMocked = true;
} else {
invariant(!isMocked); // Can't mix and match.
}
}
DEV checkInvariants();
}
HostAndPort SetState::getMatchingHost(const ReadPreferenceSetting& criteria) const {
auto hosts = getMatchingHosts(criteria);
if (hosts.empty()) {
return HostAndPort();
}
return hosts[0];
}
std::vector<HostAndPort> SetState::getMatchingHosts(const ReadPreferenceSetting& criteria) const {
switch (criteria.pref) {
// "Prefered" read preferences are defined in terms of other preferences
case ReadPreference::PrimaryPreferred: {
std::vector<HostAndPort> out =
getMatchingHosts(ReadPreferenceSetting(ReadPreference::PrimaryOnly, criteria.tags));
// NOTE: the spec says we should use the primary even if tags don't match
if (!out.empty())
return out;
return getMatchingHosts(ReadPreferenceSetting(
ReadPreference::SecondaryOnly, criteria.tags, criteria.maxStalenessSeconds));
}
case ReadPreference::SecondaryPreferred: {
std::vector<HostAndPort> out = getMatchingHosts(ReadPreferenceSetting(
ReadPreference::SecondaryOnly, criteria.tags, criteria.maxStalenessSeconds));
if (!out.empty())
return out;
// NOTE: the spec says we should use the primary even if tags don't match
return getMatchingHosts(
ReadPreferenceSetting(ReadPreference::PrimaryOnly, criteria.tags));
}
case ReadPreference::PrimaryOnly: {
// NOTE: isMaster implies isUp
Nodes::const_iterator it = std::find_if(nodes.begin(), nodes.end(), isMaster);
if (it == nodes.end())
return {};
return {it->host};
}
// The difference between these is handled by Node::matches
case ReadPreference::SecondaryOnly:
case ReadPreference::Nearest: {
std::function<bool(const Node&)> matchNode = [](const Node& node) -> bool {
return true;
};
// build comparator
if (criteria.maxStalenessSeconds.count()) {
auto masterIt = std::find_if(nodes.begin(), nodes.end(), isMaster);
if (masterIt == nodes.end() || !masterIt->lastWriteDate.toMillisSinceEpoch()) {
auto writeDateCmp = [](const Node* a, const Node* b) -> bool {
return a->lastWriteDate < b->lastWriteDate;
};
// use only non failed nodes
std::vector<const Node*> upNodes;
for (auto nodeIt = nodes.begin(); nodeIt != nodes.end(); ++nodeIt) {
if (nodeIt->isUp && nodeIt->lastWriteDate.toMillisSinceEpoch()) {
upNodes.push_back(&(*nodeIt));
}
}
auto latestSecNode =
std::max_element(upNodes.begin(), upNodes.end(), writeDateCmp);
if (latestSecNode == upNodes.end()) {
matchNode = [](const Node& node) -> bool { return false; };
} else {
Date_t maxWriteTime = (*latestSecNode)->lastWriteDate;
matchNode = [=](const Node& node) -> bool {
return duration_cast<Seconds>(maxWriteTime - node.lastWriteDate) +
refreshPeriod <=
criteria.maxStalenessSeconds;
};
}
} else {
Seconds primaryStaleness = duration_cast<Seconds>(
masterIt->lastWriteDateUpdateTime - masterIt->lastWriteDate);
matchNode = [=](const Node& node) -> bool {
return duration_cast<Seconds>(node.lastWriteDateUpdateTime -
node.lastWriteDate) -
primaryStaleness + refreshPeriod <=
criteria.maxStalenessSeconds;
};
}
}
BSONForEach(tagElem, criteria.tags.getTagBSON()) {
uassert(16358, "Tags should be a BSON object", tagElem.isABSONObj());
BSONObj tag = tagElem.Obj();
std::vector<const Node*> matchingNodes;
for (size_t i = 0; i < nodes.size(); i++) {
if (nodes[i].matches(criteria.pref) && nodes[i].matches(tag) &&
matchNode(nodes[i])) {
matchingNodes.push_back(&nodes[i]);
}
}
// don't do more complicated selection if not needed
if (matchingNodes.empty()) {
continue;
}
if (matchingNodes.size() == 1) {
return {matchingNodes.front()->host};
}
// Only consider nodes that satisfy the minOpTime
if (!criteria.minOpTime.isNull()) {
std::sort(matchingNodes.begin(), matchingNodes.end(), opTimeGreater);
for (size_t i = 0; i < matchingNodes.size(); i++) {
if (matchingNodes[i]->opTime < criteria.minOpTime) {
if (i == 0) {
// If no nodes satisfy the minOpTime criteria, we ignore the
// minOpTime requirement.
break;
}
matchingNodes.erase(matchingNodes.begin() + i, matchingNodes.end());
break;
}
}
if (matchingNodes.size() == 1) {
return {matchingNodes.front()->host};
}
}
// If there are multiple nodes satisfying the minOpTime, next order by latency
// and don't consider hosts further than a threshold from the closest.
std::sort(matchingNodes.begin(), matchingNodes.end(), compareLatencies);
for (size_t i = 1; i < matchingNodes.size(); i++) {
int64_t distance =
matchingNodes[i]->latencyMicros - matchingNodes[0]->latencyMicros;
if (distance >= latencyThresholdMicros) {
// this node and all remaining ones are too far away
matchingNodes.erase(matchingNodes.begin() + i, matchingNodes.end());
break;
}
}
std::vector<HostAndPort> hosts;
std::transform(matchingNodes.begin(),
matchingNodes.end(),
std::back_inserter(hosts),
[](const auto& node) { return node->host; });
// Note that the host list is only deterministic (or random) for the first node.
// The rest of the list is in matchingNodes order (latency) with one element swapped
// for the first element.
if (auto bestHostIdx = ReplicaSetMonitor::useDeterministicHostSelection
? roundRobin++ % hosts.size()
: rand.nextInt32(hosts.size())) {
using std::swap;
swap(hosts[0], hosts[bestHostIdx]);
}
return hosts;
}
return {};
}
default:
uassert(16337, "Unknown read preference", false);
break;
}
}
Node* SetState::findNode(const HostAndPort& host) {
const Nodes::iterator it = std::lower_bound(nodes.begin(), nodes.end(), host, compareHosts);
if (it == nodes.end() || it->host != host)
return NULL;
return &(*it);
}
Node* SetState::findOrCreateNode(const HostAndPort& host) {
// This is insertion sort, but N is currently guaranteed to be <= 12 (although this class
// must function correctly even with more nodes). If we lift that restriction, we may need
// to consider alternate algorithms.
Nodes::iterator it = std::lower_bound(nodes.begin(), nodes.end(), host, compareHosts);
if (it == nodes.end() || it->host != host) {
LOG(2) << "Adding node " << host << " to our view of replica set " << name;
it = nodes.insert(it, Node(host));
}
return &(*it);
}
void SetState::updateNodeIfInNodes(const IsMasterReply& reply) {
Node* node = findNode(reply.host);
if (!node) {
LOG(2) << "Skipping application of ismaster reply from " << reply.host
<< " since it isn't a confirmed member of set " << name;
return;
}
node->update(reply);
}
ConnectionString SetState::confirmedConnectionString() const {
std::vector<HostAndPort> hosts(begin(seedNodes), end(seedNodes));
return ConnectionString::forReplicaSet(name, std::move(hosts));
}
ConnectionString SetState::possibleConnectionString() const {
std::vector<HostAndPort> hosts;
hosts.reserve(nodes.size());
for (auto& node : nodes) {
hosts.push_back(node.host);
}
return ConnectionString::forReplicaSet(name, std::move(hosts));
}
void SetState::notify(bool finishedScan) {
const auto cachedNow = now();
for (auto it = waiters.begin(); it != waiters.end();) {
if (globalInShutdownDeprecated()) {
it->promise.setError(
{ErrorCodes::ShutdownInProgress, str::stream() << "Server is shutting down"});
waiters.erase(it++);
continue;
}
auto match = getMatchingHosts(it->criteria);
if (!match.empty()) {
// match;
it->promise.emplaceValue(std::move(match));
waiters.erase(it++);
} else if (finishedScan &&
(it->deadline <= cachedNow || areRefreshRetriesDisabledForTest.load())) {
// To preserve prior behavior, we only examine deadlines at the end of a scan.
// This ensures that we only report failure after trying to contact all hosts.
it->promise.setError(makeUnsatisfedReadPrefError(it->criteria));
waiters.erase(it++);
} else {
it++;
}
}
}
Status SetState::makeUnsatisfedReadPrefError(const ReadPreferenceSetting& criteria) const {
return Status(ErrorCodes::FailedToSatisfyReadPreference,
str::stream() << "Could not find host matching read preference "
<< criteria.toString()
<< " for set "
<< name);
}
void SetState::init() {
notifier->onFoundSet(name);
}
void SetState::drop() {
{
stdx::lock_guard<stdx::mutex> lk(mutex);
currentScan.reset();
notify(/*finishedScan*/ true);
}
// No point in notifying if we never started
if (workingConnStr.isValid()) {
notifier->onDroppedSet(name);
}
}
void SetState::checkInvariants() const {
bool foundMaster = false;
for (size_t i = 0; i < nodes.size(); i++) {
// no empty hosts
invariant(!nodes[i].host.empty());
if (nodes[i].isMaster) {
// masters must be up
invariant(nodes[i].isUp);
// at most one master
invariant(!foundMaster);
foundMaster = true;
// if we have a master it should be the same as lastSeenMaster
invariant(lastSeenMaster.empty() || nodes[i].host == lastSeenMaster);
}
// should never end up with negative latencies
invariant(nodes[i].latencyMicros >= 0);
// nodes must be sorted by host with no-dupes
invariant(i == 0 || (nodes[i - 1].host < nodes[i].host));
}
// nodes should be a (non-strict) superset of the seedNodes
invariant(std::includes(
nodes.begin(), nodes.end(), seedNodes.begin(), seedNodes.end(), compareHosts));
if (currentScan) {
// hostsToScan can't have dups or hosts already in triedHosts.
std::set<HostAndPort> cantSee = currentScan->triedHosts;
for (std::deque<HostAndPort>::const_iterator it = currentScan->hostsToScan.begin();
it != currentScan->hostsToScan.end();
++it) {
invariant(!cantSee.count(*it));
cantSee.insert(*it); // make sure we don't see this again
}
// We should only be waitingFor hosts that are in triedHosts
invariant(std::includes(currentScan->triedHosts.begin(),
currentScan->triedHosts.end(),
currentScan->waitingFor.begin(),
currentScan->waitingFor.end()));
// We should only have unconfirmedReplies if we haven't found a master yet
invariant(!currentScan->foundUpMaster || currentScan->unconfirmedReplies.empty());
}
}
template <typename Container>
void ScanState::enqueAllUntriedHosts(const Container& container, PseudoRandom& rand) {
invariant(hostsToScan.empty()); // because we don't try to dedup hosts already in the queue.
// no std::copy_if before c++11
for (typename Container::const_iterator it(container.begin()), end(container.end()); it != end;
++it) {
if (!triedHosts.count(*it)) {
hostsToScan.push_back(*it);
}
}
std::shuffle(hostsToScan.begin(), hostsToScan.end(), rand.urbg());
}
void ScanState::retryAllTriedHosts(PseudoRandom& rand) {
invariant(hostsToScan.empty()); // because we don't try to dedup hosts already in the queue.
// Move hosts that are in triedHosts but not in waitingFor from triedHosts to hostsToScan.
std::set_difference(triedHosts.begin(),
triedHosts.end(),
waitingFor.begin(),
waitingFor.end(),
std::inserter(hostsToScan, hostsToScan.end()));
std::shuffle(hostsToScan.begin(), hostsToScan.end(), rand.urbg());
triedHosts = waitingFor;
}
}
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