yuanlihan opened a new pull request #11989:
URL: https://github.com/apache/druid/pull/11989
### Description
This PR add a new cache feature for broker.
|Property|Possible Values|Description|Default|
|--------|---------------|-----------|-------|
|`druid.broker.cache.useSegmentMergedResultCache`|true, false|Enable segment
merged result cache on the Broker.|false|
|`druid.broker.cache.populateSegmentMergedResultCache`|true, false|Populate
segment merged result cache on the Broker.|false|
This new cache feature will cache merged results of historical segments on
Broker. It's expected as a better cache option for Broker in some use cases.
| | Case 1: can work when using group by v2 engine |
Case 2: can work when scanning historical segments only | Case 3: can work when
scanning both historical and realtime segments | Case 4: be efficient to cache
large number of segments |
| -------------------- | ---------------------------------------------- |
------------------------------------------------------- |
------------------------------------------------------------ |
------------------------------------------------------ |
| Segment Level cache | ✗ |
✓ | ✓
| ✗
|
| Result level cache | ✗ |
✓ | ✗
| ✓
|
| Segment merged cache | ✓ |
✓ | ✓
| ✓
|
I will try to write benchmarks to compare these cache options and may paste
benchmarks result here later
##### Key changed/added classes in this PR
* `CachingClusteredClient`
* `CacheUtil`
* `ForegroundCachePopulator`
* `BackgroundCachePopulator`
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- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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