scylladb

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Asias He eedcee7f31 gossip: Reduce unncessary VIEW_BACKLOG updates

The blacklog of current and max in VIEW_BACKLOG is not update but the
nodes are updating VIEW_BACKLOG all the time. For example:

```
INFO  2020-03-06 17:13:46,761 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.3, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486026590,718)
INFO  2020-03-06 17:13:46,821 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.2, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486026531,742)
INFO  2020-03-06 17:13:47,765 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.3, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486027590,721)
INFO  2020-03-06 17:13:47,825 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.2, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486027531,745)
INFO  2020-03-06 17:13:48,772 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.3, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486028590,726)
INFO  2020-03-06 17:13:48,833 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.2, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486028531,750)
INFO  2020-03-06 17:13:49,772 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.3, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486029590,729)
INFO  2020-03-06 17:13:49,832 [shard 0] storage_service - Update system.peers table: endpoint=127.0.0.2, app_state=VIEW_BACKLOG, versioned_value=Value(0:18446744073709551615:1583486029531,753)
```

The downside of such updates:

 - Introduces more gossip exchange traffic
 - Updates system.peers all the time

The extra unnecessary gossip traffic is fine to a cluster in a good
shape but when some of the nodes or shards are loaded, such messages and
the handling of such messages can make the system even busy.

With this patch, VIEW_BACKLOG is updated only when the backlog is really
updated.

Btw, we can even make the update only when the change of the backlog is
great than a threshold, e.g., 5%, which can reduce the traffic even
further.

Fixes #5970

2020-09-29 13:37:37 +03:00

pager

query_pager: Fix continuation handling for noop visitor

2020-09-22 10:18:01 +02:00

paxos

paxos: use schema_registry when applying accepted proposal if there is schema mismatch

2020-08-27 19:04:09 +02:00

cache_hitrate_calculator.hh

treewide: add missing headers and/or forward declarations

2020-03-23 09:29:45 +02:00

client_state.cc

codebase wide: replace count with contains