Bug: Hive may fail to detect Hadoop version when using isolated classloader
Status: Resolved | Priority: Blocker | Resolution: Fixed
Created: 09/Jul/20 15:50
Affects Version/s: 3.0.0

Spark allows the user to set `spark.sql.hive.metastore.jars` to specify jars to access Hive Metastore. These jars are loaded by the isolated classloader. Because we also share Hadoop classes with the isolated classloader, the user doesn't need to add Hadoop jars to `spark.sql.hive.metastore.jars`, which means when we are using the isolated classloader, hadoop-common jar is not available in this case. If Hadoop VersionInfo is not initialized before we switch to the isolated classloader, and we try to initialize it using the isolated classloader (the current thread context classloader), it will fail and report `Unknown` which causes Hive to throw the following exception:

{code}
java.lang.RuntimeException: Illegal Hadoop Version: Unknown (expected A.B.* format)
	at org.apache.hadoop.hive.shims.ShimLoader.getMajorVersion(ShimLoader.java:147)
	at org.apache.hadoop.hive.shims.ShimLoader.loadShims(ShimLoader.java:122)
	at org.apache.hadoop.hive.shims.ShimLoader.getHadoopShims(ShimLoader.java:88)
	at org.apache.hadoop.hive.metastore.ObjectStore.getDataSourceProps(ObjectStore.java:377)
	at org.apache.hadoop.hive.metastore.ObjectStore.setConf(ObjectStore.java:268)
	at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:76)
	at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:136)
	at org.apache.hadoop.hive.metastore.RawStoreProxy.<init>(RawStoreProxy.java:58)
	at org.apache.hadoop.hive.metastore.RawStoreProxy.getProxy(RawStoreProxy.java:67)
	at org.apache.hadoop.hive.metastore.HiveMetaStore$HMSHandler.newRawStore(HiveMetaStore.java:517)
	at org.apache.hadoop.hive.metastore.HiveMetaStore$HMSHandler.getMS(HiveMetaStore.java:482)
	at org.apache.hadoop.hive.metastore.HiveMetaStore$HMSHandler.createDefaultDB(HiveMetaStore.java:544)
	at org.apache.hadoop.hive.metastore.HiveMetaStore$HMSHandler.init(HiveMetaStore.java:370)
	at org.apache.hadoop.hive.metastore.RetryingHMSHandler.<init>(RetryingHMSHandler.java:78)
	at org.apache.hadoop.hive.metastore.RetryingHMSHandler.getProxy(RetryingHMSHandler.java:84)
	at org.apache.hadoop.hive.metastore.HiveMetaStore.newRetryingHMSHandler(HiveMetaStore.java:5762)
	at org.apache.hadoop.hive.metastore.HiveMetaStoreClient.<init>(HiveMetaStoreClient.java:219)
	at org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient.<init>(SessionHiveMetaStoreClient.java:67)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.apache.hadoop.hive.metastore.MetaStoreUtils.newInstance(MetaStoreUtils.java:1548)
	at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.<init>(RetryingMetaStoreClient.java:86)
	at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.getProxy(RetryingMetaStoreClient.java:132)
	at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.getProxy(RetryingMetaStoreClient.java:104)
	at org.apache.hadoop.hive.ql.metadata.Hive.createMetaStoreClient(Hive.java:3080)
	at org.apache.hadoop.hive.ql.metadata.Hive.getMSC(Hive.java:3108)
	at org.apache.hadoop.hive.ql.metadata.Hive.getAllFunctions(Hive.java:3349)
	at org.apache.hadoop.hive.ql.metadata.Hive.reloadFunctions(Hive.java:217)
	at org.apache.hadoop.hive.ql.metadata.Hive.registerAllFunctionsOnce(Hive.java:204)
	at org.apache.hadoop.hive.ql.metadata.Hive.<init>(Hive.java:331)
	at org.apache.hadoop.hive.ql.metadata.Hive.get(Hive.java:292)
	at org.apache.hadoop.hive.ql.metadata.Hive.getInternal(Hive.java:262)
	at org.apache.hadoop.hive.ql.metadata.Hive.get(Hive.java:247)
	at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:543)
	at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:511)
	at org.apache.spark.sql.hive.client.HiveClientImpl.newState(HiveClientImpl.scala:175)
	at org.apache.spark.sql.hive.client.HiveClientImpl.<init>(HiveClientImpl.scala:128)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.apache.spark.sql.hive.client.IsolatedClientLoader.createClient(IsolatedClientLoader.scala:301)
	at org.apache.spark.sql.hive.HiveUtils$.newClientForMetadata(HiveUtils.scala:431)
	at org.apache.spark.sql.hive.HiveUtils$.newClientForMetadata(HiveUtils.scala:324)
	at org.apache.spark.sql.hive.HiveExternalCatalog.client$lzycompute(HiveExternalCatalog.scala:72)
	at org.apache.spark.sql.hive.HiveExternalCatalog.client(HiveExternalCatalog.scala:71)
	at org.apache.spark.sql.hive.client.HadoopVersionInfoSuite.$anonfun$new$1(HadoopVersionInfoSuite.scala:63)
	at org.scalatest.OutcomeOf.outcomeOf(OutcomeOf.scala:85)
	at org.scalatest.OutcomeOf.outcomeOf$(OutcomeOf.scala:83)

{code}

Technically, This is indeed an issue of Hadoop VersionInfo which has been fixed: https://issues.apache.org/jira/browse/HADOOP-14067. But since we are still supporting old Hadoop versions, we should fix it.

Why this issue starts to happen in Spark 3.0.0?

In Spark 2.4.x, we use Hive 1.2.1 by default. It will trigger `VersionInfo` initialization in the static codes of `Hive` class. This will happen when we load `HiveClientImpl` class because `HiveClientImpl.clent` method refers to `Hive` class. At this moment, the thread context classloader is not using the isolcated classloader, so it can access hadoop-common jar on the classpath and initialize it correctly.

In Spark 3.0.0, we use Hive 2.3.7. The static codes of `Hive` class are not accessing `VersionInfo` because of the change in https://issues.apache.org/jira/browse/HIVE-11657. Instead, accessing `VersionInfo` happens when creating a `Hive` object (See the above stack trace). This happens here https://github.com/apache/spark/blob/v3.0.0/sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveClientImpl.scala#L260. But we switch to the isolated classloader before calling `HiveClientImpl.client` (See https://github.com/apache/spark/blob/v3.0.0/sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveClientImpl.scala#L283). This is exactly what I mentioned above: `If Hadoop VersionInfo is not initialized before we switch to the isolated classloader, and we try to initialize it using the isolated classloader (the current thread context classloader), it will fail`

I marked this is a blocker because it's a regression in 3.0.0 caused by upgrading Hive execution version from 1.2.1 to 2.3.7.