thevar1able/ClickHouse
1
0
Fork 0
mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-11-29 02:52:13 +00:00
Code Issues Packages Projects Releases Wiki Activity

Improvement

Browse Source
This commit is contained in:
Alexey Milovidov 2020-06-12 23:32:31 +03:00
parent cfef7ba692
commit 6ff671b092
1 changed files with 16 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
src/Storages/MergeTree/LeaderElection.h
View File

@ -29,8 +29,12 @@ namespace zkutil
* But then we decided to get rid of leader election, so every replica can become leader.
* For now, every replica can become leader if there is no leader among replicas with old version.
*
* It's tempting to remove this class at all, but we have to maintain it,
* to maintain compatibility when replicas with different versions work on the same cluster
* (this is allowed for short time period during cluster update).
*
* Replicas with old versions participate in leader election with ephemeral sequential nodes.
* If the node is first, then replica is leader.
* If the node is first, then replica is the leader.
* Replicas with new versions creates persistent sequential nodes.
* If the first node is persistent, then all replicas with new versions become leaders.
*/
@ -90,6 +94,17 @@ private:
void createNode()
{
shutdown_called = false;
/// If there is at least one persistent node, we don't have to create another.
Strings children = zookeeper.getChildren(path);
for (const auto & child : children)
{
Coordination::Stat stat;
zookeeper.get(path + "/" + child, &stat);
if (!stat.ephemeralOwner)
return;
}
zookeeper.create(path + "/leader_election-", identifier, CreateMode::PersistentSequential);
task->activateAndSchedule();
}