LantaoJin commented on a change in pull request #23951:
[SPARK-13704][CORE][YARN] Re-implement RackResolver to reduce resolving time
URL: https://github.com/apache/spark/pull/23951#discussion_r267179410
##########
File path:
resource-managers/yarn/src/main/scala/org/apache/spark/deploy/yarn/SparkRackResolver.scala
##########
@@ -17,24 +17,90 @@
package org.apache.spark.deploy.yarn
+import scala.collection.JavaConverters._
+import scala.collection.mutable.ArrayBuffer
+
+import com.google.common.base.Strings
import org.apache.hadoop.conf.Configuration
+import org.apache.hadoop.fs.CommonConfigurationKeysPublic
+import org.apache.hadoop.net._
+import org.apache.hadoop.util.ReflectionUtils
import org.apache.hadoop.yarn.util.RackResolver
import org.apache.log4j.{Level, Logger}
+import org.apache.spark.internal.Logging
+
/**
- * Wrapper around YARN's [[RackResolver]]. This allows Spark tests to easily
override the
+ * Re-implement YARN's [[RackResolver]]. This allows Spark tests to easily
override the
* default behavior, since YARN's class self-initializes the first time it's
called, and
* future calls all use the initial configuration.
*/
-private[yarn] class SparkRackResolver {
+private[spark] class SparkRackResolver {
// RackResolver logs an INFO message whenever it resolves a rack, which is
way too often.
if (Logger.getLogger(classOf[RackResolver]).getLevel == null) {
Logger.getLogger(classOf[RackResolver]).setLevel(Level.WARN)
}
def resolve(conf: Configuration, hostName: String): String = {
- RackResolver.resolve(conf, hostName).getNetworkLocation()
+ SparkRackResolver.coreResolve(conf, List(hostName)).head.getNetworkLocation
+ }
+
+ /**
+ * Added in SPARK-27038.
+ * This should be changed to `RackResolver.resolve(conf, hostNames)`
+ * in hadoop releases with YARN-9332.
+ */
+ def resolve(conf: Configuration, hostNames: List[String]): List[Node] = {
+ SparkRackResolver.coreResolve(conf, hostNames)
}
+}
+/**
+ * Utility to resolve the rack for hosts in an efficient manner.
+ * It will cache the rack for individual hosts to avoid
+ * repeatedly performing the same expensive lookup.
+ *
+ * Its logic refers [[org.apache.hadoop.yarn.util.RackResolver]] and enhanced.
+ * This will be unnecessary in hadoop releases with YARN-9332.
+ * With that, we could just directly use
[[org.apache.hadoop.yarn.util.RackResolver]].
+ * In the meantime, this is a re-implementation for spark's use.
+ */
+object SparkRackResolver extends Logging {
+ private var dnsToSwitchMapping: DNSToSwitchMapping = _
+ private var initCalled = false
+
+ def coreResolve(conf: Configuration, hostNames: List[String]): List[Node] = {
+ if (!initCalled) {
Review comment:
Every calling of `get` in different threads will generate a new
SparkResolver since the `conf` instances are different. So how to keep only one
cache in memory?
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