Supply AwakenRegion messages in StoreheartbeatResponse.

[LykxSassinator]

Development Task

This issue is a development task referred to tikv/tikv#13648.
It's used to supply extra AwakenRegion message in StoreheartbeatResponse to wake up hibernated regions timely, for reducing time-cost on TiKV cluster failure recovery.

[rleungx]

Will it bring more pressure for PD to handle the heartbeat when the cluster is large?

[LykxSassinator]

Will it bring more pressure for PD to handle the heartbeat when the cluster is large?

Nope, the extra message just contains several StoreID, so-called slow-store in it, having minor impacts to the original StoreHeartbeatResponse processing. And the checking of slow-store is fast as it just checks the metadata of StoreInfo.

[rleungx]

Will it bring more pressure for PD to handle the heartbeat when the cluster is large?

Nope, the extra message just contains several StoreID, so-called slow-store in it, having minor impacts to the original StoreHeartbeatResponse processing. And the checking of slow-store is fast as it just checks the metadata of StoreInfo.

What I mean is not the cost of handling the store heartbeat but the cost of processing the region heartbeat if the hibernate region is awakened frequently.

[LykxSassinator]

Will it bring more pressure for PD to handle the heartbeat when the cluster is large?

Nope, the extra message just contains several StoreID, so-called slow-store in it, having minor impacts to the original StoreHeartbeatResponse processing. And the checking of slow-store is fast as it just checks the metadata of StoreInfo.

What I mean is not the cost of handling the store heartbeat but the cost of processing the region heartbeat if the hibernate region is awakened frequently.

Good point. We also considered this case both in PD&TiKV sides.

• In the implementation in TiKV, we just wake up regions whose leaders exist in abnormal nodes, marked in AwakenRegions.abnormal_stores. So, the count of awaken regions is acceptable to PD. And heartbeats from awaken regions are less in this way.
• Only if there exists slow stores in the cluster, will PD send AwakenRegions to TiKV nodes.