For partitioned logs, mutations of the same version may be sent to applier
out-of-order. If one loader advances to the next version, an applier may
receive later version mutations for different loaders. So, dropping of early
mutations is wrong.
The subsequence number is needed so that mutations of the same commit version
number, but from different partitioned logs can be correctly reassembled in
order.
For old backup files, the sub number is always 0. For partitioned mutation
logs, the actual sub number is used. For range files, the sub number is always
0.
An actor is schedulable to run if the current worker has enough resourc, i.e.,
the worker's memory usage is below the threshold;
Exception: If the actor is working on the current version batch, we have to schedule
the actor to run to avoid dead-lock.
Future: When we release the actors that are blocked by memory usage, we should release them
in increasing order of their version batch.
RestoreMaster may not receive all acks. for the last command, i.e., finishRestore,
because RestoreLoaders and RestoreAppliers exit immediately after sending the ack.
If the ack is lost, it will not be resent.
This commit also removes some unneeded code.
This commit passes 50k random tests without errors.
1) Use the runRYWTransaction for simple DB access
2) Replace some printf with TraceEvent
3) Remove printf not used in debugging
4) Avoid wait inside the condition in loop-choose-when for
the core routine of restore worker, loader and applier.
5) Rename Restore.actor.cpp to RestoreWorker.actor.cpp since
the file only has functionalities related to restore worker.
Passed correctness test
1) Add sendBatchRequests and getBatchReplies
sendBatchRequests is a generic actor to send requests without
processing replies.
getBatchReplies is similar to sendBatchRequests expect that
it returns the reply to caller.
2) Share applier interface to loaders by using RequestStream,
instead of using DB.
Create RestoreSysInfo struct, similar purpose as DBInfo, for
the restore system information that are shared among restore workers.
Add a NotifiedVersion into an applier data which represents
the smallest version the applier is at.
When a loader sends mutation vector to appliers, it sends
the request that contains prevVersion and commitVersion.
This commits also put actor into an actorCollector for
loop-choose-when situation.
sfc-gh-tclinkenbeard