[GitHub] [druid] sthetland commented on a change in pull request #9407: query laning and load shedding

[GitBox <gi...@apache.org>]

sthetland commented on a change in pull request #9407: query laning and load shedding
URL: https://github.com/apache/druid/pull/9407#discussion_r389988957
 
 

 ##########
 File path: docs/configuration/index.md
 ##########
 @@ -1476,9 +1476,35 @@ These Broker configurations can be defined in the `broker/runtime.properties` fi
 |`druid.broker.select.tier`|`highestPriority`, `lowestPriority`, `custom`|If segments are cross-replicated across tiers in a cluster, you can tell the broker to prefer to select segments in a tier with a certain priority.|`highestPriority`|
 |`druid.broker.select.tier.custom.priorities`|`An array of integer priorities.`|Select servers in tiers with a custom priority list.|None|
 
+##### Query laning
+
+The Broker provides facilities to aid in query capacity reservation for heterogeneous query workloads in the form of 'laning' strategies, which provide a variety of mechanisms to examine and classify a query, assigning it to a 'lane'. Lanes are defined with capacity limits which the broker will enforce, causing requests in excess of the capacity to be discarded with an HTTP 429 status code, reserving resources for other lanes or for interactive queries (with no lane).
+
+|Property|Description|Default|
+|--------|-----------|-------|
+|`druid.query.scheduler.numThreads`|Maximum number of HTTP threads to dedicate to query processing. To save HTTP thread capacity, this should be lower than `druid.server.http.numThreads`.|Unbounded|
+|`druid.query.scheduler.laning.strategy`|Query laning strategy to use to assign queries to a lane in order to control capacities for certain classes of queries.|`none`|
+
+##### Laning strategies
+
+###### No laning strategy
+
+In this mode, queries are never assigned lane, and concurrent query count will only limited by `druid.server.http.numThreads` or `druid.query.scheduler.numThreads`, if set. This is the default Druid query scheduler operating mode. This strategy can also be explicitly enabled by setting `druid.query.scheduler.laning.strategy` to `none`.
 
 Review comment:
   ```suggestion
   In this mode, queries are never assigned a lane, and the concurrent query count will only be limited by `druid.server.http.numThreads` or `druid.query.scheduler.numThreads`, if set. This is the default Druid query scheduler operating mode. Enable this strategy explicitly by setting `druid.query.scheduler.laning.strategy` to `none`.
   ```

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