private long assignLeader(int partitionId, List<Long> children) {
// We used masterHostId = -1 as a way to force the leader choice to be
// the first replica in the list, if we don't have some other mechanism
// which has successfully overridden it.
int masterHostId = -1;
if (m_state.get() == AppointerState.CLUSTER_START) {
try {
// find master in topo
JSONArray parts = m_topo.getJSONArray("partitions");
for (int p = 0; p < parts.length(); p++) {
JSONObject aPartition = parts.getJSONObject(p);
int pid = aPartition.getInt("partition_id");
if (pid == partitionId) {
masterHostId = aPartition.getInt("master");
}
}
} catch (JSONException jse) {
tmLog.error("Failed to find master for partition " + partitionId + ", defaulting to 0");
jse.printStackTrace();
masterHostId = -1; // stupid default
}
} else {
// For now, if we're appointing a new leader as a result of a
// failure, just pick the first replica in the children list.
// Could eventually do something more complex here to try to keep a
// semi-balance, but it's unclear that this has much utility until
// we add rebalancing on rejoin as well.
masterHostId = -1;
}
long masterHSId = children.get(0);
for (Long child : children) {
if (CoreUtils.getHostIdFromHSId(child) == masterHostId) {
masterHSId = child;
break;
}
}
tmLog.info(
"Appointing HSId "
+ CoreUtils.hsIdToString(masterHSId)
+ " as leader for partition "
+ partitionId);
try {
m_iv2appointees.put(partitionId, masterHSId);
} catch (Exception e) {
VoltDB.crashLocalVoltDB("Unable to appoint new master for partition " + partitionId, true, e);
}
return masterHSId;
}
@Override
public void run(List<String> children) {
List<Long> updatedHSIds = VoltZK.childrenToReplicaHSIds(children);
// compute previously unseen HSId set in the callback list
Set<Long> newHSIds = new HashSet<Long>(updatedHSIds);
newHSIds.removeAll(m_replicas);
tmLog.debug("Newly seen replicas: " + CoreUtils.hsIdCollectionToString(newHSIds));
// compute previously seen but now vanished from the callback list HSId set
Set<Long> missingHSIds = new HashSet<Long>(m_replicas);
missingHSIds.removeAll(updatedHSIds);
tmLog.debug("Newly dead replicas: " + CoreUtils.hsIdCollectionToString(missingHSIds));
tmLog.debug(
"Handling babysitter callback for partition "
+ m_partitionId
+ ": children: "
+ CoreUtils.hsIdCollectionToString(updatedHSIds));
if (m_state.get() == AppointerState.CLUSTER_START) {
// We can't yet tolerate a host failure during startup. Crash it all
if (missingHSIds.size() > 0) {
VoltDB.crashGlobalVoltDB("Node failure detected during startup.", false, null);
}
// ENG-3166: Eventually we would like to get rid of the extra replicas beyond k_factor,
// but for now we just look to see how many replicas of this partition we actually expect
// and gate leader assignment on that many copies showing up.
int replicaCount = m_kfactor + 1;
JSONArray parts;
try {
parts = m_topo.getJSONArray("partitions");
for (int p = 0; p < parts.length(); p++) {
JSONObject aPartition = parts.getJSONObject(p);
int pid = aPartition.getInt("partition_id");
if (pid == m_partitionId) {
replicaCount = aPartition.getJSONArray("replicas").length();
}
}
} catch (JSONException e) {
// Ignore and just assume the normal number of replicas
}
if (children.size() == replicaCount) {
m_currentLeader = assignLeader(m_partitionId, updatedHSIds);
} else {
tmLog.info(
"Waiting on "
+ ((m_kfactor + 1) - children.size())
+ " more nodes "
+ "for k-safety before startup");
}
} else {
// Check for k-safety
if (!isClusterKSafe()) {
VoltDB.crashGlobalVoltDB(
"Some partitions have no replicas. Cluster has become unviable.", false, null);
}
// Check if replay has completed
if (m_replayComplete.get() == false) {
VoltDB.crashGlobalVoltDB(
"Detected node failure during command log replay. Cluster will shut down.",
false,
null);
}
// Check to see if there's been a possible network partition and we're not already handling
// it
if (m_partitionDetectionEnabled && !m_partitionDetected) {
doPartitionDetectionActivities();
}
// If we survived the above gauntlet of fail, appoint a new leader for this partition.
if (missingHSIds.contains(m_currentLeader)) {
m_currentLeader = assignLeader(m_partitionId, updatedHSIds);
}
}
m_replicas.clear();
m_replicas.addAll(updatedHSIds);
}