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arangodb/arangod/Agency/Agent.cpp

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////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
/// http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Kaveh Vahedipour
////////////////////////////////////////////////////////////////////////////////
#include "Agent.h"
#include <velocypack/Iterator.h>
#include <velocypack/velocypack-aliases.h>
#include <chrono>
#include <thread>
#include "Agency/GossipCallback.h"
#include "Basics/ConditionLocker.h"
#include "Basics/ReadLocker.h"
#include "Basics/WriteLocker.h"
#include "RestServer/DatabaseFeature.h"
#include "RestServer/QueryRegistryFeature.h"
#include "VocBase/vocbase.h"
using namespace arangodb::application_features;
using namespace arangodb::velocypack;
using namespace std::chrono;
namespace arangodb {
namespace consensus {
// Instanciations of some declarations in AgencyCommon.h:
std::string const pubApiPrefix("/_api/agency/");
std::string const privApiPrefix("/_api/agency_priv/");
std::string const NO_LEADER("");
/// Agent configuration
Agent::Agent(config_t const& config)
: Thread("Agent"),
_config(config),
_commitIndex(0),
_spearhead(this),
_readDB(this),
_transient(this),
_agentNeedsWakeup(false),
_compactor(this),
_ready(false),
_preparing(0) {
_state.configure(this);
_constituent.configure(this);
if (size() > 1) {
_inception = std::make_unique<Inception>(this);
} else {
_leaderSince = 0;
}
}
/// This agent's id
std::string Agent::id() const { return _config.id(); }
/// Agent's id is set once from state machine
bool Agent::id(std::string const& id) {
bool success;
if ((success = _config.setId(id))) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "My id is " << id;
} else {
LOG_TOPIC(ERR, Logger::AGENCY)
<< "Cannot reassign id once set: My id is " << _config.id()
<< " reassignment to " << id;
}
return success;
}
/// Merge command line and persisted comfigurations
bool Agent::mergeConfiguration(VPackSlice const& persisted) {
return _config.merge(persisted); // Concurrency managed in merge
}
/// Dtor shuts down thread
Agent::~Agent() {
waitForThreadsStop();
// This usually was already done called from AgencyFeature::unprepare,
// but since this only waits for the threads to stop, it can be done
// multiple times, and we do it just in case the Agent object was
// created but never really started. Here, we exit with a fatal error
// if the threads do not stop in time.
}
/// Wait until threads are terminated:
void Agent::waitForThreadsStop() {
// It is allowed to call this multiple times, we do so from the constructor
// and from AgencyFeature::unprepare.
int counter = 0;
while (_constituent.isRunning() || _compactor.isRunning() ||
(_config.supervision() && _supervision.isRunning()) ||
(_inception != nullptr && _inception->isRunning())) {
std::this_thread::sleep_for(std::chrono::microseconds(100000));
// fail fatally after 5 mins:
if (++counter >= 10 * 60 * 5) {
LOG_TOPIC(FATAL, Logger::AGENCY) << "some agency thread did not finish";
FATAL_ERROR_EXIT();
}
}
shutdown(); // wait for the main Agent thread to terminate
}
/// State machine
State const& Agent::state() const {
return _state;
}
/// Start all agent thread
bool Agent::start() {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Starting agency comm worker.";
Thread::start();
return true;
}
/// Get all logs from state machine
query_t Agent::allLogs() const {
return _state.allLogs();
}
/// This agent's term
term_t Agent::term() const {
return _constituent.term();
}
/// Agency size
size_t Agent::size() const {
return _config.size();
}
/// My endpoint
std::string Agent::endpoint() const {
return _config.endpoint();
}
/// Handle voting
priv_rpc_ret_t Agent::requestVote(
term_t termOfPeer, std::string const& id, index_t lastLogIndex,
index_t lastLogTerm, query_t const& query, int64_t timeoutMult) {
if (timeoutMult != -1 && timeoutMult != _config.timeoutMult()) {
adjustTimeoutMult(timeoutMult);
LOG_TOPIC(WARN, Logger::AGENCY) << "Voter: setting timeout multiplier to "
<< timeoutMult << " for next term.";
}
bool doIVote = _constituent.vote(termOfPeer, id, lastLogIndex, lastLogTerm);
return priv_rpc_ret_t(doIVote, this->term());
}
/// Get copy of momentary configuration
config_t const Agent::config() const {
return _config;
}
/// Adjust timeoutMult:
void Agent::adjustTimeoutMult(int64_t timeoutMult) {
_config.setTimeoutMult(timeoutMult);
}
/// Get timeoutMult:
int64_t Agent::getTimeoutMult() const {
return _config.timeoutMult();
}
/// Leader's id
std::string Agent::leaderID() const {
return _constituent.leaderID();
}
/// Are we leading?
bool Agent::leading() const {
// When we become leader, we are first entering a preparation phase.
// Note that this method returns true regardless of whether we
// are still preparing or not. The preparation phases 1 and 2 are
// indicated by the _preparing member in the Agent, the Constituent is
// already LEADER.
// The Constituent has to send out AppendEntriesRPC calls immediately, but
// only when we are properly leading (with initialized stores etc.)
// can we execute requests.
return _constituent.leading();
}
// Waits here for confirmation of log's commits up to index. Timeout in seconds.
AgentInterface::raft_commit_t Agent::waitFor(index_t index, double timeout) {
if (size() == 1) { // single host agency
return Agent::raft_commit_t::OK;
}
auto startTime = steady_clock::now();
index_t lastCommitIndex = 0;
// Wait until woken up through AgentCallback
while (true) {
/// success?
/// (_waitForCV's mutex stops writes to _commitIndex)
CONDITION_LOCKER(guard, _waitForCV);
if (leading()) {
if (lastCommitIndex != _commitIndex) {
// We restart the timeout computation if there has been progress:
startTime = steady_clock::now();
}
lastCommitIndex = _commitIndex;
if (lastCommitIndex >= index) {
return Agent::raft_commit_t::OK;
}
} else {
return Agent::raft_commit_t::UNKNOWN;
}
duration<double> d = steady_clock::now() - startTime;
LOG_TOPIC(DEBUG, Logger::AGENCY) << "waitFor: index: " << index <<
" _commitIndex: " << _commitIndex << " _lastCommitIndex: " <<
lastCommitIndex << " elapsedTime: " << d.count();
if (d.count() >= timeout) {
return Agent::raft_commit_t::TIMEOUT;
}
// Go to sleep:
_waitForCV.wait(static_cast<uint64_t>(1.0e6 * (timeout - d.count())));
// shutting down
if (this->isStopping()) {
return Agent::raft_commit_t::UNKNOWN;
}
}
// We should never get here
TRI_ASSERT(false);
return Agent::raft_commit_t::UNKNOWN;
}
// Check if log is committed up to index.
bool Agent::isCommitted(index_t index) {
if (size() == 1) { // single host agency
return true;
}
CONDITION_LOCKER(guard, _waitForCV);
if (leading()) {
return _commitIndex >= index;
} else {
return false;
}
}
// AgentCallback reports id of follower and its highest processed index
void Agent::reportIn(std::string const& peerId, index_t index, size_t toLog) {
auto startTime = steady_clock::now();
// only update the time stamps here:
{
MUTEX_LOCKER(tiLocker, _tiLock);
// Update last acknowledged answer
auto t = steady_clock::now();
std::chrono::duration<double> d = t - _lastAcked[peerId];
auto secsSince = d.count();
if (secsSince < 1.5e9 && peerId != id()
&& secsSince > _config.minPing() * _config.timeoutMult()) {
LOG_TOPIC(WARN, Logger::AGENCY)
<< "Last confirmation from peer " << peerId
<< " was received more than minPing ago: " << secsSince;
}
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Setting _lastAcked[" << peerId << "] to time "
<< std::chrono::duration_cast<std::chrono::microseconds>(
t.time_since_epoch()).count();
_lastAcked[peerId] = t;
if (index > _confirmed[peerId]) { // progress this follower?
_confirmed[peerId] = index;
if (toLog > 0) { // We want to reset the wait time only if a package callback
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Got call back of " << toLog << " logs, resetting _earliestPackage to now for id " << peerId;
_earliestPackage[peerId] = steady_clock::now();
}
wakeupMainLoop(); // only necessary for non-empty callbacks
}
}
duration<double> reportInTime = steady_clock::now() - startTime;
if (reportInTime.count() > 0.1) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "reportIn took longer than 0.1s: " << reportInTime.count();
}
}
/// @brief Report a failed append entry call from AgentCallback
void Agent::reportFailed(std::string const& slaveId, size_t toLog) {
if (toLog > 0) {
// This is only used for non-empty appendEntriesRPC calls. If such calls
// fail, we have to set this earliestPackage time to now such that the
// main thread tries again immediately:
MUTEX_LOCKER(guard, _tiLock);
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Resetting _earliestPackage to now for id " << slaveId;
_earliestPackage[slaveId] = steady_clock::now();
}
}
/// Followers' append entries
priv_rpc_ret_t Agent::recvAppendEntriesRPC(
term_t term, std::string const& leaderId, index_t prevIndex, term_t prevTerm,
index_t leaderCommitIndex, query_t const& queries) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Got AppendEntriesRPC from "
<< leaderId << " with term " << term;
term_t t(this->term());
if (!ready()) { // We have not been able to put together our configuration
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Agent is not ready yet.";
return priv_rpc_ret_t(false,t);
}
VPackSlice payload = queries->slice();
// Update commit index
if (payload.type() != VPackValueType::Array) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Received malformed entries for appending. Discarding!";
return priv_rpc_ret_t(false,t);
}
if (!_constituent.checkLeader(term, leaderId, prevIndex, prevTerm)) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Not accepting appendEntries from " << leaderId;
return priv_rpc_ret_t(false,t);
}
size_t nqs = payload.length();
if (nqs == 0) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Finished empty AppendEntriesRPC from "
<< leaderId << " with term " << term;
return priv_rpc_ret_t(true,t);
}
bool ok = true;
index_t lastIndex = 0; // Index of last entry in our log
try {
lastIndex = _state.logFollower(queries);
if (lastIndex < payload[nqs-1].get("index").getNumber<index_t>()) {
// We could not log all the entries in this query, we need to report
// this to the leader!
ok = false;
}
} catch (std::exception const& e) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Exception during log append: " << __FILE__ << __LINE__
<< " " << e.what();
}
{
WRITE_LOCKER(oLocker, _outputLock);
CONDITION_LOCKER(guard, _waitForCV);
_commitIndex = std::max(
_commitIndex, std::min(leaderCommitIndex, lastIndex));
_waitForCV.broadcast();
if (_commitIndex >= _state.nextCompactionAfter()) {
_compactor.wakeUp();
}
}
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Finished AppendEntriesRPC from "
<< leaderId << " with term " << term;
return priv_rpc_ret_t(ok,t);
}
/// Leader's append entries
void Agent::sendAppendEntriesRPC() {
auto cc = ClusterComm::instance();
if (cc == nullptr) {
// nullptr only happens during controlled shutdown
return;
}
// _lastSent only accessed in main thread
std::string const myid = id();
for (auto const& followerId : _config.active()) {
if (followerId != myid && leading()) {
term_t t(0);
index_t lastConfirmed;
auto startTime = steady_clock::now();
SteadyTimePoint earliestPackage;
SteadyTimePoint lastAcked;
{
t = this->term();
MUTEX_LOCKER(tiLocker, _tiLock);
lastConfirmed = _confirmed[followerId];
lastAcked = _lastAcked[followerId];
earliestPackage = _earliestPackage[followerId];
}
if (
((steady_clock::now() - earliestPackage).count() < 0)) {
continue;
}
duration<double> lockTime = steady_clock::now() - startTime;
if (lockTime.count() > 0.1) {
LOG_TOPIC(WARN, Logger::AGENCY)
<< "Reading lastConfirmed took too long: " << lockTime.count();
}
index_t commitIndex;
{
READ_LOCKER(oLocker, _outputLock);
commitIndex = _commitIndex;
}
std::vector<log_t> unconfirmed = _state.get(lastConfirmed, lastConfirmed+99);
lockTime = steady_clock::now() - startTime;
if (lockTime.count() > 0.2) {
LOG_TOPIC(WARN, Logger::AGENCY)
<< "Finding unconfirmed entries took too long: " << lockTime.count();
}
// Note that despite compaction this vector can never be empty, since
// any compaction keeps at least one active log entry!
if (unconfirmed.empty()) {
LOG_TOPIC(ERR, Logger::AGENCY) << "Unexpected empty unconfirmed: "
<< "lastConfirmed=" << lastConfirmed << " commitIndex="
<< commitIndex;
}
TRI_ASSERT(!unconfirmed.empty());
if (unconfirmed.size() == 1) {
// Note that this case means that everything we have is already
// confirmed, since we always get everything from (and including!)
// the last confirmed entry.
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Nothing to append.";
continue;
}
duration<double> m = steady_clock::now() - _lastSent[followerId];
if (m.count() > _config.minPing() &&
_lastSent[followerId].time_since_epoch().count() != 0) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Note: sent out last AppendEntriesRPC "
<< "to follower " << followerId << " more than minPing ago: "
<< m.count() << " lastAcked: "
<< duration_cast<duration<double>>(lastAcked.time_since_epoch()).count();
}
index_t lowest = unconfirmed.front().index;
bool needSnapshot = false;
Store snapshot(this, "snapshot");
index_t snapshotIndex;
term_t snapshotTerm;
if (lowest > lastConfirmed) {
// Ooops, compaction has thrown away so many log entries that
// we cannot actually update the follower. We need to send our
// latest snapshot instead:
needSnapshot = true;
bool success = false;
try {
success = _state.loadLastCompactedSnapshot(snapshot,
snapshotIndex, snapshotTerm);
} catch (std::exception const& e) {
LOG_TOPIC(WARN, Logger::AGENCY)
<< "Exception thrown by loadLastCompactedSnapshot: "
<< e.what();
}
if (!success) {
LOG_TOPIC(WARN, Logger::AGENCY)
<< "Could not load last compacted snapshot, not sending appendEntriesRPC!";
continue;
}
if (snapshotTerm == 0) {
// No shapshot yet
needSnapshot = false;
}
}
// RPC path
std::stringstream path;
index_t prevLogIndex = unconfirmed.front().index;
index_t prevLogTerm = unconfirmed.front().term;
if (needSnapshot) {
prevLogIndex = snapshotIndex;
prevLogTerm = snapshotTerm;
}
{
path << "/_api/agency_priv/appendEntries?term=" << t << "&leaderId="
<< id() << "&prevLogIndex=" << prevLogIndex
<< "&prevLogTerm=" << prevLogTerm << "&leaderCommit=" << commitIndex
<< "&senderTimeStamp=" << std::llround(steadyClockToDouble() * 1000);
}
// Body
Builder builder;
builder.add(VPackValue(VPackValueType::Array));
if (needSnapshot) {
{ VPackObjectBuilder guard(&builder);
builder.add(VPackValue("readDB"));
{ VPackArrayBuilder guard2(&builder);
snapshot.dumpToBuilder(builder);
}
builder.add("term", VPackValue(snapshotTerm));
builder.add("index", VPackValue(snapshotIndex));
}
}
size_t toLog = 0;
index_t highest = 0;
for (size_t i = 0; i < unconfirmed.size(); ++i) {
auto const& entry = unconfirmed.at(i);
if (entry.index > lastConfirmed) {
builder.add(VPackValue(VPackValueType::Object));
builder.add("index", VPackValue(entry.index));
builder.add("term", VPackValue(entry.term));
builder.add("query", VPackSlice(entry.entry->data()));
builder.add("clientId", VPackValue(entry.clientId));
builder.close();
highest = entry.index;
++toLog;
}
}
builder.close();
// Really leading?
if (challengeLeadership()) {
resign();
return;
}
// Postpone sending the next message for 30 seconds or until an
// error or successful result occurs.
earliestPackage = steady_clock::now() + std::chrono::seconds(30);
{
MUTEX_LOCKER(tiLocker, _tiLock);
_earliestPackage[followerId] = earliestPackage;
}
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Setting _earliestPackage to now + 30s for id " << followerId;
// Send request
auto headerFields =
std::make_unique<std::unordered_map<std::string, std::string>>();
cc->asyncRequest(
"1", 1, _config.poolAt(followerId),
arangodb::rest::RequestType::POST, path.str(),
std::make_shared<std::string>(builder.toJson()), headerFields,
std::make_shared<AgentCallback>(this, followerId, highest, toLog),
150.0, true);
// Note the timeout is relatively long, but due to the 30 seconds
// above, we only ever have at most 5 messages in flight.
_lastSent[followerId] = steady_clock::now();
// _constituent.notifyHeartbeatSent(followerId);
// Do not notify constituent, because the AppendEntriesRPC here could
// take a very long time, so this must not disturb the empty ones
// being sent out.
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Appending (" << (uint64_t) (TRI_microtime() * 1000000000.0) << ") "
<< unconfirmed.size() - 1 << " entries up to index "
<< highest << (needSnapshot ? " and a snapshot" : "")
<< " to follower " << followerId
<< ". Next real log contact to " << followerId<< " in: "
<< std::chrono::duration<double, std::milli>(
earliestPackage - steady_clock::now()).count() << "ms";
}
}
}
void Agent::resign(term_t otherTerm) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Resigning in term "
<< _constituent.term() << " because of peer's term " << otherTerm;
_constituent.follow(otherTerm, NO_LEADER);
endPrepareLeadership();
}
/// Leader's append entries, empty ones for heartbeat, triggered by Constituent
void Agent::sendEmptyAppendEntriesRPC(std::string followerId) {
auto cc = ClusterComm::instance();
if (cc == nullptr) {
// nullptr only happens during controlled shutdown
return;
}
if (!leading()) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Not sending empty appendEntriesRPC to follower " << followerId
<< " because we are no longer leading.";
return;
}
index_t commitIndex;
{
READ_LOCKER(oLocker, _outputLock);
commitIndex = _commitIndex;
}
// RPC path
std::stringstream path;
{
path << "/_api/agency_priv/appendEntries?term=" << _constituent.term()
<< "&leaderId=" << id() << "&prevLogIndex=0"
<< "&prevLogTerm=0&leaderCommit=" << commitIndex
<< "&senderTimeStamp=" << std::llround(steadyClockToDouble() * 1000);
}
// Just check once more:
if (!leading()) {
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Not sending empty appendEntriesRPC to follower " << followerId
<< " because we are no longer leading.";
return;
}
// Send request
auto headerFields =
std::make_unique<std::unordered_map<std::string, std::string>>();
cc->asyncRequest(
"1", 1, _config.poolAt(followerId),
arangodb::rest::RequestType::POST, path.str(),
std::make_shared<std::string>("[]"), headerFields,
std::make_shared<AgentCallback>(this, followerId, 0, 0),
3 * _config.minPing() * _config.timeoutMult(), true);
_constituent.notifyHeartbeatSent(followerId);
double now = TRI_microtime();
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Sending empty appendEntriesRPC to follower " << followerId;
double diff = TRI_microtime() - now;
if (diff > 0.01) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Logging of a line took more than 1/100 of a second, this is bad:" << diff;
}
}
void Agent::advanceCommitIndex() {
// Determine median _confirmed value of followers:
std::vector<index_t> temp;
{
MUTEX_LOCKER(_tiLocker, _tiLock);
for (auto const& id: config().active()) {
if (_confirmed.find(id) != _confirmed.end()) {
temp.push_back(_confirmed[id]);
}
}
}
index_t quorum = size() / 2 + 1;
if (temp.size() < quorum) {
LOG_TOPIC(WARN, Logger::AGENCY) << "_confirmed not populated, quorum: " << quorum << ".";
return;
}
std::sort(temp.begin(), temp.end());
index_t index = temp[temp.size() - quorum];
term_t t = _constituent.term();
{
WRITE_LOCKER(oLocker, _outputLock);
if (index > _commitIndex) {
CONDITION_LOCKER(guard, _waitForCV);
LOG_TOPIC(TRACE, Logger::AGENCY)
<< "Critical mass for commiting " << _commitIndex + 1
<< " through " << index << " to read db";
// Change _readDB and _commitIndex atomically together:
_readDB.applyLogEntries(
_state.slices( /* inform others by callbacks */
_commitIndex + 1, index), _commitIndex, t, true);
_commitIndex = index;
// Wake up rest handlers:
_waitForCV.broadcast();
if (_commitIndex >= _state.nextCompactionAfter()) {
_compactor.wakeUp();
}
}
}
}
// Check if I am member of active agency
bool Agent::active() const {
std::vector<std::string> active = _config.active();
return (find(active.begin(), active.end(), id()) != active.end());
}
/// @brief Activate agency (Inception thread for multi-host, main thread else)
void Agent::activateAgency() {
_config.activate();
try {
_state.persistActiveAgents(
_config.activeToBuilder(), _config.poolToBuilder());
} catch (std::exception const& e) {
LOG_TOPIC(FATAL, Logger::AGENCY)
<< "Failed to persist active agency: " << e.what();
FATAL_ERROR_EXIT();
}
}
/// Load persistent state called once
void Agent::load() {
DatabaseFeature* database =
ApplicationServer::getFeature<DatabaseFeature>("Database");
auto vocbase = database->systemDatabase();
auto queryRegistry = QueryRegistryFeature::QUERY_REGISTRY;
if (vocbase == nullptr) {
LOG_TOPIC(FATAL, Logger::AGENCY) << "could not determine _system database";
FATAL_ERROR_EXIT();
}
{
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(guard, _ioLock); // need this for callback to set _spearhead
// Note that _state.loadCollections eventually does a callback to the
// setPersistedState method, which acquires _outputLock and _waitForCV.
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Loading persistent state.";
if (!_state.loadCollections(vocbase, queryRegistry, _config.waitForSync())) {
LOG_TOPIC(FATAL, Logger::AGENCY)
<< "Failed to load persistent state on startup.";
FATAL_ERROR_EXIT();
}
}
// Note that the agent thread is terminated immediately when there is only
// one agent, since no AppendEntriesRPC have to be issued. Therefore,
// this thread is almost certainly terminated (and thus isStopping() returns
// true), when we get here.
if (size() > 1 && this->isStopping()) {
return;
}
wakeupMainLoop();
_compactor.start();
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Starting spearhead worker.";
_constituent.start(vocbase, queryRegistry);
persistConfiguration(term());
if (_config.supervision()) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Starting cluster sanity facilities";
_supervision.start(this);
}
if (_inception != nullptr) { // resilient agency only
_inception->start();
} else {
MUTEX_LOCKER(guard, _ioLock); // need this for callback to set _spearhead
READ_LOCKER(guard2, _outputLock);
_spearhead = _readDB;
activateAgency();
}
}
/// Still leading? Under MUTEX from ::read or ::write
bool Agent::challengeLeadership() {
MUTEX_LOCKER(tiLocker, _tiLock);
size_t good = 0;
std::string const myid = id();
for (auto const& i : _lastAcked) {
if (i.first != myid) { // do not count ourselves
duration<double> m = steady_clock::now() - i.second;
LOG_TOPIC(DEBUG, Logger::AGENCY) << "challengeLeadership: found "
"_lastAcked[" << i.first << "] to be " << m.count() << " seconds in the past.";
// This is rather arbitrary here: We used to have 0.9 here to absolutely
// ensure that a leader resigns before another one even starts an election.
// However, the Raft paper does not mention this at all. Rather, in the
// paper it is written that the leader should resign immediately if it
// sees a higher term from another server. Currently we have not
// implemented to return the follower's term with a response to
// AppendEntriesRPC, so the leader cannot find out a higher term this
// way. The leader can, however, see a higher term in the incoming
// AppendEntriesRPC a new leader sends out, and it will immediately
// resign if it sees that. For the moment, this value here can stay.
// We should soon implement sending the follower's term back with
// each response and probably get rid of this method altogether,
// but this requires a bit more thought.
if (_config.maxPing() * _config.timeoutMult() > m.count()) {
++good;
}
}
}
LOG_TOPIC(DEBUG, Logger::AGENCY) << "challengeLeadership: good=" << good;
return (good < size() / 2); // not counting myself
}
/// Get last acknowledged responses on leader
query_t Agent::lastAckedAgo() const {
std::unordered_map<std::string, SteadyTimePoint> lastAcked;
{
MUTEX_LOCKER(tiLocker, _tiLock);
lastAcked = _lastAcked;
}
auto ret = std::make_shared<Builder>();
ret->openObject();
if (leading()) {
for (auto const& i : lastAcked) {
ret->add(i.first, VPackValue(
1.0e-3 * std::floor(
(i.first!=id() ?
duration<double>(steady_clock::now()-i.second).count()*1.0e3 :
0.0))));
}
}
ret->close();
return ret;
}
trans_ret_t Agent::transact(query_t const& queries) {
arangodb::consensus::index_t maxind = 0; // maximum write index
// Note that we are leading (_constituent.leading()) if and only
// if _constituent.leaderId == our own ID. Therefore, we do not have
// to use leading() or _constituent.leading() here, but can simply
// look at the leaderID.
auto leader = _constituent.leaderID();
if (leader != id()) {
return trans_ret_t(false, leader);
}
{
CONDITION_LOCKER(guard, _waitForCV);
while (getPrepareLeadership() != 0) {
_waitForCV.wait(100);
}
}
// Apply to spearhead and get indices for log entries
auto qs = queries->slice();
addTrxsOngoing(qs); // remember that these are ongoing
size_t failed;
auto ret = std::make_shared<arangodb::velocypack::Builder>();
{
TRI_DEFER(removeTrxsOngoing(qs));
// Note that once the transactions are in our log, we can remove them
// from the list of ongoing ones, although they might not yet be committed.
// This is because then, inquire will find them in the log and draw its
// own conclusions. The map of ongoing trxs is only to cover the time
// from when we receive the request until we have appended the trxs
// ourselves.
ret = std::make_shared<arangodb::velocypack::Builder>();
failed = 0;
ret->openArray();
// Only leader else redirect
if (challengeLeadership()) {
resign();
return trans_ret_t(false, NO_LEADER);
}
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
for (const auto& query : VPackArrayIterator(qs)) {
if (query[0].isObject()) {
check_ret_t res = _spearhead.applyTransaction(query);
if(res.successful()) {
maxind = (query.length() == 3 && query[2].isString()) ?
_state.logLeaderSingle(query[0], term(), query[2].copyString()) :
_state.logLeaderSingle(query[0], term());
ret->add(VPackValue(maxind));
} else {
_spearhead.read(res.failed->slice(), *ret);
++failed;
}
} else if (query[0].isString()) {
_spearhead.read(query, *ret);
}
}
ret->close();
}
// Report that leader has persisted
reportIn(id(), maxind);
if (size() == 1) {
advanceCommitIndex();
}
return trans_ret_t(true, id(), maxind, failed, ret);
}
// Non-persistent write to non-persisted key-value store
trans_ret_t Agent::transient(query_t const& queries) {
// Note that we are leading (_constituent.leading()) if and only
// if _constituent.leaderId == our own ID. Therefore, we do not have
// to use leading() or _constituent.leading() here, but can simply
// look at the leaderID.
auto leader = _constituent.leaderID();
if (leader != id()) {
return trans_ret_t(false, leader);
}
{
CONDITION_LOCKER(guard, _waitForCV);
while (getPrepareLeadership() != 0) {
_waitForCV.wait(100);
}
}
auto ret = std::make_shared<arangodb::velocypack::Builder>();
// Apply to spearhead and get indices for log entries
{
VPackArrayBuilder b(ret.get());
// Only leader else redirect
if (challengeLeadership()) {
resign();
return trans_ret_t(false, NO_LEADER);
}
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
// Read and writes
for (const auto& query : VPackArrayIterator(queries->slice())) {
if (query[0].isObject()) {
ret->add(VPackValue(_transient.applyTransaction(query).successful()));
} else if (query[0].isString()) {
_transient.read(query, *ret);
}
}
}
return trans_ret_t(true, id(), 0, 0, ret);
}
write_ret_t Agent::inquire(query_t const& query) {
// Note that we are leading (_constituent.leading()) if and only
// if _constituent.leaderId == our own ID. Therefore, we do not have
// to use leading() or _constituent.leading() here, but can simply
// look at the leaderID.
auto leader = _constituent.leaderID();
if (leader != id()) {
return write_ret_t(false, leader);
}
write_ret_t ret;
while (true) {
// Check ongoing ones:
bool found = false;
for (auto const& s : VPackArrayIterator(query->slice())) {
std::string ss = s.copyString();
if (isTrxOngoing(ss)) {
found = true;
break;
}
}
if (!found) {
break;
}
std::this_thread::sleep_for(std::chrono::duration<double>(0.1));
leader = _constituent.leaderID();
if (leader != id()) {
return write_ret_t(false, leader);
}
}
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
ret.indices = _state.inquire(query);
ret.accepted = true;
return ret;
}
/// Write new entries to replicated state and store
write_ret_t Agent::write(query_t const& query, bool discardStartup) {
std::vector<bool> applied;
std::vector<index_t> indices;
auto multihost = size()>1;
// Note that we are leading (_constituent.leading()) if and only
// if _constituent.leaderId == our own ID. Therefore, we do not have
// to use leading() or _constituent.leading() here, but can simply
// look at the leaderID.
auto leader = _constituent.leaderID();
if (multihost && leader != id()) {
return write_ret_t(false, leader);
}
if (!discardStartup) {
CONDITION_LOCKER(guard, _waitForCV);
while (getPrepareLeadership() != 0) {
_waitForCV.wait(100);
}
}
{
addTrxsOngoing(query->slice()); // remember that these are ongoing
TRI_DEFER(removeTrxsOngoing(query->slice()));
// Note that once the transactions are in our log, we can remove them
// from the list of ongoing ones, although they might not yet be committed.
// This is because then, inquire will find them in the log and draw its
// own conclusions. The map of ongoing trxs is only to cover the time
// from when we receive the request until we have appended the trxs
// ourselves.
auto slice = query->slice();
size_t ntrans = slice.length();
size_t npacks = ntrans/_config.maxAppendSize();
if (ntrans%_config.maxAppendSize()!=0) {
npacks++;
}
// Apply to spearhead and get indices for log entries
// Avoid keeping lock indefinitely
for (size_t i = 0, l = 0; i < npacks; ++i) {
query_t chunk = std::make_shared<Builder>();
{
VPackArrayBuilder b(chunk.get());
for (size_t j = 0; j < _config.maxAppendSize() && l < ntrans; ++j, ++l) {
chunk->add(slice.at(l));
}
}
// Only leader else redirect
if (multihost && challengeLeadership()) {
resign();
return write_ret_t(false, NO_LEADER);
}
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
applied = _spearhead.applyTransactions(chunk);
auto tmp = _state.logLeaderMulti(chunk, applied, term());
indices.insert(indices.end(), tmp.begin(), tmp.end());
}
}
// Maximum log index
index_t maxind = 0;
if (!indices.empty()) {
maxind = *std::max_element(indices.begin(), indices.end());
}
// Report that leader has persisted
reportIn(id(), maxind);
if (size() == 1) {
advanceCommitIndex();
}
return write_ret_t(true, id(), applied, indices);
}
/// Read from store
read_ret_t Agent::read(query_t const& query) {
// Note that we are leading (_constituent.leading()) if and only
// if _constituent.leaderId == our own ID. Therefore, we do not have
// to use leading() or _constituent.leading() here, but can simply
// look at the leaderID.
auto leader = _constituent.leaderID();
if (leader != id()) {
return read_ret_t(false, leader);
}
{
CONDITION_LOCKER(guard, _waitForCV);
while (getPrepareLeadership() != 0) {
_waitForCV.wait(100);
}
}
// Only leader else redirect
if (challengeLeadership()) {
resign();
return read_ret_t(false, NO_LEADER);
}
std::string leaderId = _constituent.leaderID();
READ_LOCKER(oLocker, _outputLock);
// Retrieve data from readDB
auto result = std::make_shared<arangodb::velocypack::Builder>();
std::vector<bool> success = _readDB.read(query, result);
return read_ret_t(true, leaderId, success, result);
}
/// Send out append entries to followers regularly or on event
void Agent::run() {
// Only run in case we are in multi-host mode
while (!this->isStopping() && size() > 1) {
{
// We set the variable to false here, if any change happens during
// or after the calls in this loop, this will be set to true to
// indicate no sleeping. Any change will happen under the mutex.
CONDITION_LOCKER(guard, _appendCV);
_agentNeedsWakeup = false;
}
if (leading() && getPrepareLeadership() == 1) {
// If we are officially leading but the _preparing flag is set, we
// are in the process of preparing for leadership. This flag is
// set when the Constituent celebrates an election victory. Here,
// in the main thread, we do the actual preparations:
if (!prepareLead()) {
_constituent.follow(0); // do not change _term or _votedFor
} else {
// we need to start work as leader
lead();
}
donePrepareLeadership(); // we are ready to roll, except that we
// have to wait for the _commitIndex to
// reach the end of our log
}
// Leader working only
if (leading()) {
if (1 == getPrepareLeadership()) {
// Skip the usual work and the waiting such that above preparation
// code runs immediately. We will return with value 2 such that
// replication and confirmation of it can happen. Service will
// continue once _commitIndex has reached the end of the log and then
// getPrepareLeadership() will finally return 0.
continue;
}
// Challenge leadership.
// Let's proactively know, that we no longer lead instead of finding out
// through read/write.
if (challengeLeadership()) {
resign();
continue;
}
// Append entries to followers
sendAppendEntriesRPC();
// Check whether we can advance _commitIndex
advanceCommitIndex();
bool commenceService = false;
{
READ_LOCKER(oLocker, _outputLock);
if (leading() && getPrepareLeadership() == 2 &&
_commitIndex == _state.lastIndex()) {
commenceService = true;
}
}
if (commenceService) {
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
READ_LOCKER(oLocker, _outputLock);
_spearhead = _readDB;
endPrepareLeadership(); // finally service can commence
}
// Go to sleep some:
{
CONDITION_LOCKER(guard, _appendCV);
if (!_agentNeedsWakeup) {
// wait up to minPing():
_appendCV.wait(static_cast<uint64_t>(1.0e6 * _config.minPing()));
// We leave minPing here without the multiplier to run this
// loop often enough in cases of high load.
}
}
} else {
CONDITION_LOCKER(guard, _appendCV);
if (!_agentNeedsWakeup) {
_appendCV.wait(1000000);
}
}
}
}
void Agent::persistConfiguration(term_t t) {
// Agency configuration
auto agency = std::make_shared<Builder>();
{ VPackArrayBuilder trxs(agency.get());
{ VPackArrayBuilder trx(agency.get());
{ VPackObjectBuilder oper(agency.get());
agency->add(VPackValue(".agency"));
{ VPackObjectBuilder a(agency.get());
agency->add("term", VPackValue(t));
agency->add("id", VPackValue(id()));
agency->add("active", _config.activeToBuilder()->slice());
agency->add("pool", _config.poolToBuilder()->slice());
agency->add("size", VPackValue(size()));
agency->add("timeoutMult", VPackValue(_config.timeoutMult()));
}}}}
// In case we've lost leadership, no harm will arise as the failed write
// prevents bogus agency configuration to be replicated among agents. ***
write(agency, true);
}
/// Orderly shutdown
void Agent::beginShutdown() {
Thread::beginShutdown();
// Stop constituent and key value stores
_constituent.beginShutdown();
// Stop supervision
if (_config.supervision()) {
_supervision.beginShutdown();
}
// Stop inception process
if (_inception != nullptr) { // resilient agency only
_inception->beginShutdown();
}
// Compactor
_compactor.beginShutdown();
// Wake up all waiting rest handlers
{
CONDITION_LOCKER(guard, _waitForCV);
_waitForCV.broadcast();
}
// Wake up run
wakeupMainLoop();
}
bool Agent::prepareLead() {
{
// Erase _earliestPackage, which allows for immediate sending of
// AppendEntriesRPC when we become a leader.
MUTEX_LOCKER(tiLocker, _tiLock);
_earliestPackage.clear();
}
// Key value stores
try {
rebuildDBs();
} catch (std::exception const& e) {
LOG_TOPIC(ERR, Logger::AGENCY)
<< "Failed to rebuild key value stores." << e.what();
return false;
}
// Reset last acknowledged
{
MUTEX_LOCKER(tiLocker, _tiLock);
for (auto const& i : _config.active()) {
_lastAcked[i] = steady_clock::now();
}
}
return true;
}
/// Becoming leader
void Agent::lead() {
{
// We cannot start sendAppendentries before first log index.
// Any missing indices before _commitIndex were compacted.
// DO NOT EDIT without understanding the consequences for sendAppendEntries!
index_t commitIndex;
{
READ_LOCKER(oLocker, _outputLock);
commitIndex = _commitIndex;
}
MUTEX_LOCKER(tiLocker, _tiLock);
for (auto& i : _confirmed) {
if (i.first != id()) {
i.second = commitIndex;
}
}
}
// Agency configuration
term_t myterm;
myterm = _constituent.term();
persistConfiguration(myterm);
// This is all right now, in the main loop we will wait until a
// majority of all servers have replicated this configuration.
// Then we will copy the _readDB to the _spearhead and start service.
}
// How long back did I take over leadership, result in seconds
int64_t Agent::leaderFor() const {
return std::chrono::duration_cast<std::chrono::duration<int64_t>>(
std::chrono::steady_clock::now().time_since_epoch()).count() - _leaderSince;
}
// Notify inactive pool members of configuration change()
void Agent::notifyInactive() const {
auto cc = ClusterComm::instance();
if (cc == nullptr) {
// nullptr only happens during controlled shutdown
return;
}
std::unordered_map<std::string, std::string> pool = _config.pool();
std::string path = "/_api/agency_priv/inform";
Builder out;
{
VPackObjectBuilder o(&out);
out.add("term", VPackValue(term()));
out.add("id", VPackValue(id()));
out.add("active", _config.activeToBuilder()->slice());
out.add("pool", _config.poolToBuilder()->slice());
out.add("min ping", VPackValue(_config.minPing()));
out.add("max ping", VPackValue(_config.maxPing()));
out.add("timeoutMult", VPackValue(_config.timeoutMult()));
}
for (auto const& p : pool) {
if (p.first != id()) {
auto headerFields =
std::make_unique<std::unordered_map<std::string, std::string>>();
cc->asyncRequest("1", 1, p.second, arangodb::rest::RequestType::POST,
path, std::make_shared<std::string>(out.toJson()),
headerFields, nullptr, 1.0, true);
}
}
}
void Agent::updatePeerEndpoint(query_t const& message) {
VPackSlice slice = message->slice();
if (!slice.isObject() || slice.length() == 0) {
THROW_ARANGO_EXCEPTION_MESSAGE(
TRI_ERROR_AGENCY_INFORM_MUST_BE_OBJECT,
std::string("Inproper greeting: ") + slice.toJson());
}
std::string uuid, endpoint;
try {
uuid = slice.keyAt(0).copyString();
} catch (std::exception const& e) {
THROW_ARANGO_EXCEPTION_MESSAGE(
TRI_ERROR_AGENCY_INFORM_MUST_BE_OBJECT,
std::string("Cannot deal with UUID: ") + e.what());
}
try {
endpoint = slice.valueAt(0).copyString();
} catch (std::exception const& e) {
THROW_ARANGO_EXCEPTION_MESSAGE(
TRI_ERROR_AGENCY_INFORM_MUST_BE_OBJECT,
std::string("Cannot deal with UUID: ") + e.what());
}
updatePeerEndpoint(uuid, endpoint);
}
void Agent::updatePeerEndpoint(std::string const& id, std::string const& ep) {
if (_config.updateEndpoint(id, ep)) {
if (!challengeLeadership()) {
persistConfiguration(term());
notifyInactive();
}
}
}
void Agent::notify(query_t const& message) {
VPackSlice slice = message->slice();
if (!slice.isObject()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
TRI_ERROR_AGENCY_INFORM_MUST_BE_OBJECT,
std::string("Inform message must be an object. Incoming type is ") +
slice.typeName());
}
if (!slice.hasKey("id") || !slice.get("id").isString()) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_ID);
}
if (!slice.hasKey("term")) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_TERM);
}
_constituent.update(slice.get("id").copyString(),
slice.get("term").getUInt());
if (!slice.hasKey("active") || !slice.get("active").isArray()) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_ACTIVE);
}
if (!slice.hasKey("pool") || !slice.get("pool").isObject()) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_POOL);
}
if (!slice.hasKey("min ping") || !slice.get("min ping").isNumber()) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_MIN_PING);
}
if (!slice.hasKey("max ping") || !slice.get("max ping").isNumber()) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_MAX_PING);
}
if (!slice.hasKey("timeoutMult") || !slice.get("timeoutMult").isInteger()) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_INFORM_MUST_CONTAIN_TIMEOUT_MULT);
}
_config.update(message);
_state.persistActiveAgents(_config.activeToBuilder(), _config.poolToBuilder());
}
// Rebuild key value stores
void Agent::rebuildDBs() {
term_t term = _constituent.term();
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
WRITE_LOCKER(oLocker, _outputLock);
CONDITION_LOCKER(guard, _waitForCV);
index_t lastCompactionIndex;
// We must go back to clean sheet
_readDB.clear();
_spearhead.clear();
if (!_state.loadLastCompactedSnapshot(_readDB, lastCompactionIndex, term)) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_CANNOT_REBUILD_DBS);
}
_commitIndex = lastCompactionIndex;
_waitForCV.broadcast();
// Apply logs from last applied index to leader's commit index
LOG_TOPIC(DEBUG, Logger::AGENCY)
<< "Rebuilding key-value stores from index "
<< lastCompactionIndex << " to " << _commitIndex << " " << _state;
{
auto logs = _state.slices(lastCompactionIndex+1, _commitIndex);
_readDB.applyLogEntries(logs, _commitIndex, term,
false /* do not send callbacks */);
}
_spearhead = _readDB;
LOG_TOPIC(INFO, Logger::AGENCY)
<< id() << " rebuilt key-value stores - serving.";
}
/// Compact read db
void Agent::compact() {
// We do not allow the case _config.compactionKeepSize() == 0, since
// we need to keep a part of the recent log. Therefore we cannot use
// the _readDB ever, since we have to compute a state of the key/value
// space well before _commitIndex anyway. Apart from this, the compaction
// code runs on the followers as well where we do not have a _readDB
// anyway.
index_t commitIndex;
{
READ_LOCKER(guard, _outputLock);
commitIndex = _commitIndex;
}
if (commitIndex > _config.compactionKeepSize()) {
// If the keep size is too large, we do not yet compact
// TODO: check if there is at problem that we call State::compact()
// now with a commit index that may have been slightly modified by other
// threads
// TODO: the question is if we have to lock out others while we
// call compact or while we grab _commitIndex and then call compact
if (!_state.compact(commitIndex - _config.compactionKeepSize())) {
LOG_TOPIC(WARN, Logger::AGENCY) << "Compaction for index "
<< commitIndex - _config.compactionKeepSize()
<< " did not work.";
}
}
}
/// Last commit index
arangodb::consensus::index_t Agent::lastCommitted() const {
READ_LOCKER(oLocker, _outputLock);
return _commitIndex;
}
/// Last log entry
log_t Agent::lastLog() const { return _state.lastLog(); }
/// Get spearhead
Store const& Agent::spearhead() const { return _spearhead; }
/// Get _readDB reference with intentionally no lock acquired here.
/// Safe ONLY IF via executeLock() (see example Supervisor.cpp)
Store const& Agent::readDB() const {
return _readDB;
}
/// Get readdb
arangodb::consensus::index_t Agent::readDB(Node& node) const {
READ_LOCKER(oLocker, _outputLock);
node = _readDB.get();
return _commitIndex;
}
void Agent::executeLockedRead(std::function<void()> const& cb) {
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
READ_LOCKER(oLocker, _outputLock);
cb();
}
void Agent::executeLockedWrite(std::function<void()> const& cb) {
_tiLock.assertNotLockedByCurrentThread();
MUTEX_LOCKER(ioLocker, _ioLock);
WRITE_LOCKER(oLocker, _outputLock);
CONDITION_LOCKER(guard, _waitForCV);
cb();
}
/// Get transient
/// intentionally no lock is acquired here, so we can return
/// a const reference
/// the caller has to make sure the lock is actually held
Store const& Agent::transient() const {
_ioLock.assertLockedByCurrentThread();
return _transient;
}
/// Rebuild from persisted state
void Agent::setPersistedState(VPackSlice const& compaction) {
// Catch up with compacted state, this is only called at startup
_spearhead = compaction.get("readDB");
// Catch up with commit
try {
WRITE_LOCKER(oLocker, _outputLock);
CONDITION_LOCKER(guard, _waitForCV);
_readDB = compaction.get("readDB");
_commitIndex =
arangodb::basics::StringUtils::uint64(compaction.get("_key").copyString());
_waitForCV.broadcast();
} catch (std::exception const& e) {
LOG_TOPIC(ERR, Logger::AGENCY) << e.what() << " " << __FILE__ << __LINE__;
}
}
/// Are we still starting up?
bool Agent::booting() { return (!_config.poolComplete()); }
/// We expect an object as follows {id:<id>,endpoint:<endpoint>,pool:{...}}
/// key: uuid value: endpoint
/// Lock configuration and compare
/// Add whatever is missing in our list.
/// Compare whatever is in our list already. (ASSERT identity)
/// If I know more immediately contact peer with my list.
query_t Agent::gossip(query_t const& in, bool isCallback, size_t version) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "Incoming gossip: "
<< in->slice().toJson();
VPackSlice slice = in->slice();
if (!slice.isObject()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
20001,
std::string("Gossip message must be an object. Incoming type is ") +
slice.typeName());
}
if (!slice.hasKey("id") || !slice.get("id").isString()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
20002, "Gossip message must contain string parameter 'id'");
}
std::string id = slice.get("id").copyString();
if (!slice.hasKey("endpoint") || !slice.get("endpoint").isString()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
20003, "Gossip message must contain string parameter 'endpoint'");
}
std::string endpoint = slice.get("endpoint").copyString();
if ( _inception != nullptr && isCallback) {
_inception->reportVersionForEp(endpoint, version);
}
// If pool complete but knabe is not member => reject at all times
if (_config.poolComplete()) {
auto pool = _config.pool();
if (pool.find(id) == pool.end()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
20003, "Gossip message from new peer while my pool is complete.");
}
}
LOG_TOPIC(TRACE, Logger::AGENCY)
<< "Gossip " << ((isCallback) ? "callback" : "call") << " from "
<< endpoint;
if (!slice.hasKey("pool") || !slice.get("pool").isObject()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
20003, "Gossip message must contain object parameter 'pool'");
}
VPackSlice pslice = slice.get("pool");
LOG_TOPIC(TRACE, Logger::AGENCY) << "Received gossip " << slice.toJson();
for (auto const& pair : VPackObjectIterator(pslice)) {
if (!pair.value.isString()) {
THROW_ARANGO_EXCEPTION_MESSAGE(
20004, "Gossip message pool must contain string parameters");
}
}
query_t out = std::make_shared<Builder>();
{
VPackObjectBuilder b(out.get());
std::vector<std::string> gossipPeers = _config.gossipPeers();
if (!gossipPeers.empty()) {
try {
_config.eraseFromGossipPeers(endpoint);
} catch (std::exception const& e) {
LOG_TOPIC(ERR, Logger::AGENCY)
<< __FILE__ << ":" << __LINE__ << " " << e.what();
}
}
/// disagreement over pool membership: fatal!
if (!_config.upsertPool(pslice, id)) {
LOG_TOPIC(FATAL, Logger::AGENCY) << "Discrepancy in agent pool!";
FATAL_ERROR_EXIT();
}
if (!isCallback) { // no gain in callback to a callback.
auto pool = _config.pool();
auto active = _config.active();
// Wrapped in envelope in RestAgencyPrivHandler
out->add(VPackValue("pool"));
{
VPackObjectBuilder bb(out.get());
for (auto const& i : pool) {
out->add(i.first, VPackValue(i.second));
}
}
}
}
if (!isCallback) {
LOG_TOPIC(TRACE, Logger::AGENCY) << "Answering with gossip "
<< out->slice().toJson();
}
return out;
}
void Agent::resetRAFTTimes(double min_timeout, double max_timeout) {
_config.pingTimes(min_timeout,max_timeout);
}
void Agent::ready(bool b) {
// From main thread of Inception
_ready = b;
}
bool Agent::ready() const {
if (size() == 1) {
return true;
}
return _ready;
}
query_t Agent::buildDB(arangodb::consensus::index_t index) {
Store store(this);
index_t oldIndex;
term_t term;
if (!_state.loadLastCompactedSnapshot(store, oldIndex, term)) {
THROW_ARANGO_EXCEPTION(TRI_ERROR_AGENCY_CANNOT_REBUILD_DBS);
}
{
READ_LOCKER(oLocker, _outputLock);
if (index > _commitIndex) {
LOG_TOPIC(INFO, Logger::AGENCY)
<< "Cannot snapshot beyond leaderCommitIndex: " << _commitIndex;
index = _commitIndex;
} else if (index < oldIndex) {
LOG_TOPIC(INFO, Logger::AGENCY)
<< "Cannot snapshot before last compaction index: " << oldIndex;
index = oldIndex;
}
}
{
if (index > oldIndex) {
auto logs = _state.slices(oldIndex+1, index);
store.applyLogEntries(logs, index, term,
false /* do not perform callbacks */);
} else {
VPackBuilder logs;
logs.openArray();
logs.close();
store.applyLogEntries(logs, index, term,
false /* do not perform callbacks */);
}
}
auto builder = std::make_shared<VPackBuilder>();
store.toBuilder(*builder);
return builder;
}
void Agent::addTrxsOngoing(Slice trxs) {
try {
MUTEX_LOCKER(guard,_trxsLock);
for (auto const& trx : VPackArrayIterator(trxs)) {
if (trx.isArray() && trx.length() == 3 && trx[0].isObject() && trx[2].isString()) {
// only those are interesting:
_ongoingTrxs.insert(trx[2].copyString());
}
}
} catch (...) {
}
}
void Agent::removeTrxsOngoing(Slice trxs) {
try {
MUTEX_LOCKER(guard, _trxsLock);
for (auto const& trx : VPackArrayIterator(trxs)) {
if (trx.isArray() && trx.length() == 3 && trx[0].isObject() && trx[2].isString()) {
// only those are interesting:
_ongoingTrxs.erase(trx[2].copyString());
}
}
} catch (...) {
}
}
bool Agent::isTrxOngoing(std::string& id) {
try {
MUTEX_LOCKER(guard, _trxsLock);
auto it = _ongoingTrxs.find(id);
return it != _ongoingTrxs.end();
} catch (...) {
return false;
}
}
Inception const* Agent::inception() const {
return _inception.get();
}
}} // namespace
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