基于scala 怎么使用druid

Druid是一种高性能分布式列存储系统，可以用来实时查询大规模数据集。使用Scala可以通过Druid的Java API进行连接。

首先，可以使用以下Maven依赖项来引入Druid：

<dependency>
  <groupId>org.apache.druid</groupId>
  <artifactId>druid-processing</artifactId>
  <version>{druid.version}</version>
</dependency>

<dependency>
  <groupId>org.apache.druid</groupId>
  <artifactId>druid-client</artifactId>
  <version>{druid.version}</version>
</dependency>

<dependency>
  <groupId>org.apache.druid</groupId>
  <artifactId>druid-query</artifactId>
  <version>{druid.version}</version>
</dependency>

接下来，可以初始化Druid服务的配置，然后创建Druid连接池：

import io.druid.client.{DruidDataSource, DruidServer}
import io.druid.curator.discovery.{ServerDiscoveryFactory, CuratorDruidNodeDiscovery}
import io.druid.curator.{CuratorConfig, CuratorUtils}
import io.druid.java.util.common.logger.Logger
import io.druid.client.selector.ServerSelector
import io.druid.client.selector.ServerSupplier
import io.druid.client.selector.curator.{CuratorServerDiscoverySelector, CuratorServerDiscoveryProvider}
import io.druid.query.Query

val druidHost: String = "<druid-hostname>"
val druidPort: Int = <druid-port>

// Configuring Druid service
val druidServer: DruidServer = new DruidServer("my-druid-server", druidHost, druidPort, "https", null, null)
val serverDiscoveryFactory: ServerDiscoveryFactory[Void] = CuratorUtils.makeInjector().getInstance(classOf[ServerDiscoveryFactory[Void]])

val serverDiscovery = new CuratorDruidNodeDiscovery(
  serverDiscoveryFactory, // Can be any implementation of ServerDiscoveryFactory[V]
  new CuratorConfig("<zookeeper-connect>", 3000, 1000, Optional.empty(), "/druid", false, false),
  new Logger {}) // Logger used for debug

val provider = new CuratorServerDiscoveryProvider(serverDiscovery, Query.DEFAULT_INTERVAL)
val selector: ServerSelector = new CuratorServerDiscoverySelector(provider)

// Create Druid Connection pool
val druidDataSource = new DruidDataSource()
druidDataSource.setServerDiscovery(selector)
druidDataSource.setMaxConnectionIdleTime(1000L)
druidDataSource.setDiscoveryPeriodMillis(5000L) // Period to recheck available Druid servers
druidDataSource.start()

现在可以使用`druidDataSource`连接池对象执行Druid查询，并获得响应结果。例如，这里是一个基本的Druid查询：

import io.druid.java.util.common.guava.Sequence
import io.druid.query.{Query, QuerySegmentWalker}
import io.druid.query.aggregation.Aggregation
import io.druid.query.aggregation.PostAggregation
import io.druid.query.filter.Filter
import io.druid.query.spec.MultipleIntervalSegmentSpec

def executeDruidQuery[T <: Aggregation, U <: PostAggregation](
  aggregation: T,
  postAggregation: U,
  filter: Filter,
  intervals: List[String]): Sequence[_] = {

  val query = DruidQuery.newDruidQuery
    .aggregation(aggregation)
    .postAggregation(postAggregation)
    .dataSource("my-druid-data-source") // Replace with your own data source name
    .granularity("ALL")
    .filter(filter)
    .intervals(new MultipleIntervalSegmentSpec(intervals.asJava))
    .descending(false)
    .build()

  val walker: QuerySegmentWalker = druidDataSource.getQueryRunner(query)
  walker.run(query, Map.empty[String, Object]()).toList.asJava
}

这应该将Druid响应返回为`Sequence`对象，您可以对其进行相应的处理。