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arangodb
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Fix agency election lockstep bug. (#9348) 

* Fix agency election lockstep bug.

Reset the base point for the random election timeout to now whenever we have
cast a vote, be it for us or for some other server.

* CHANGELOG.
This commit is contained in:
Max Neunhöffer 2019-06-27 21:05:59 +02:00 committed by GitHub
parent 32c6a3768a
commit 5f9423057d
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3 changed files with 23 additions and 4 deletions
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8
CHANGELOG
View File

@ -1,9 +1,6 @@
v3.4.8 (XXXX-XX-XX)
-------------------
* reduce resident memory usage when creating non-unique indexes with the RocksDB storage engine
v3.4.7 (2019-07-02)
-------------------
@ -81,6 +78,11 @@ v3.4.7 (2019-07-02)
* Fix agency's handling of object assignments with TTL
* reduce resident memory usage when creating non-unique indexes with the RocksDB storage engine
* Fix agency election bug.
v3.4.6.1 (2019-06-05)
---------------------

14
arangod/Agency/Constituent.cpp
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@ -393,6 +393,10 @@ bool Constituent::vote(term_t termOfPeer, std::string const& id,
if (_votedFor != NO_LEADER) { // already voted in this term
if (_votedFor == id) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "repeating vote for " << id;
// Set the last heart beat seen to now, to grant the other guy some time
// to establish itself as a leader, before we call for another election:
_lastHeartbeatSeen = TRI_microtime();
LOG_TOPIC(TRACE, Logger::AGENCY) << "setting last heartbeat time to now, since we repeated a vote grant: " << _lastHeartbeatSeen;
return true;
}
LOG_TOPIC(DEBUG, Logger::AGENCY)
@ -408,6 +412,10 @@ bool Constituent::vote(term_t termOfPeer, std::string const& id,
if (prevLogTerm > myLastLogEntry.term ||
(prevLogTerm == myLastLogEntry.term && prevLogIndex >= myLastLogEntry.index)) {
LOG_TOPIC(DEBUG, Logger::AGENCY) << "voting for " << id << " in term " << _term;
// Set the last heart beat seen to now, to grant the other guy some time
// to establish itself as a leader, before we call for another election:
_lastHeartbeatSeen = TRI_microtime();
LOG_TOPIC(TRACE, Logger::AGENCY) << "setting last heartbeat time to now, since we granted a vote: " << _lastHeartbeatSeen;
termNoLock(_term, id);
return true;
}
@ -700,6 +708,12 @@ void Constituent::run() {
} else if (role == CANDIDATE) {
callElection(); // Run for office
// Now we take this point of time as the next base point for a
// potential next random timeout, since we have just cast a vote for
// ourselves:
_lastHeartbeatSeen = TRI_microtime();
LOG_TOPIC(TRACE, Logger::AGENCY) << "setting last heartbeat because we voted for us: " << _lastHeartbeatSeen;
} else {
double interval =
0.25 * _agent->config().minPing() * _agent->config().timeoutMult();

5
arangod/Agency/Constituent.h
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@ -156,7 +156,10 @@ class Constituent : public Thread {
std::string _id; // My own id
// Last time an AppendEntriesRPC message has arrived, this is used to
// organize out-of-patience in the follower:
// organize out-of-patience in the follower. Note that this variable is
// also set to the current time when a vote is cast, either for ourselves
// or for somebody else. The constituent calls for an election if and only
// if the time since _lastHeartbeatSeen is greater than a random timeout:
std::atomic<double> _lastHeartbeatSeen;
role_t _role; // My role