Add a new role for ratekeeper.
Remove StorageServerChanges from data distribution.
Ratekeeper monitors storage servers, which borrows the idea from
DataDistribution.
Let cluster controller to start a new data distributor role by sending a
message to a chosen worker.
Change MasterInterface usage in DataDistribution to masterId
Add DataDistributor rejoin handling.
This allows the data distributor to tell the new cluster controller of its
existence so that the controller doesn't spawn a new one. I.e., there should
be only ONE data distributor in the cluster.
If DataDistributor (DD) doesn't join in a while, then ClusterController (CC) tries
to recruit one as DD. CC also monitors DD and restarts one if it failed.
The Proxy is also monitoring the DD. If DD failed, the Proxy will ask CC for
the new DD.
Add GetRecoveryInfo RPC to master server, which is called by data distributor
to obtain the recovery Transaction version from the master server.
Fixed a couple of bugs
1) A rare race condition where a worker is being roles even after it died.
2) Fix how RoleFitness is calculated for TLog and LogRouter. Only worst fitness is compared to see if a better fit is available.
Current server team collection logic does not consider
the fact that multipe storage servers can run on the same machine.
When multiple machines fail, all servers on the machines will fail, and
the possibility of having one process team fail and lose data is very high.
To reduce the possibility of losing data when multiple machine fails,
we first create machine teams which span across different fault zones;
we then create server teams based on machine teams by
first picking 1 machine team, and then
picking 1 server from each machine in the machine team.
Signed-off-by: Meng Xu <meng_xu@apple.com>
allAlternatives failed logic was simplified, because we are already doing a global rate limiting, so a per shard limit is unnecessary
reduced unnecessary state variables in waitMetrics requests
wait_for_good_recruitment now requires that you have the desired count of each roll
remote recruitment is given a much longer wait_for_good_recruitment time interval, which does not start until enough remote machines have registered
The previous order of fitness was
BestFit > GoodFit > BestOtherFit > ...
which is baffling. It's now:
BestFit > GoodFit > OkayFit > ...
which won't break anyone's expectations.
added configuration options for the remote data center and satellite data centers
updated cluster controller recruitment logic
refactors how master writes core state
updated log recovery, and log system peeking
A.J. Beamon