Cheolsoo Park created SPARK-10970:
-------------------------------------

             Summary: Executors overload Hive metastore by making massive 
connections at execution time
                 Key: SPARK-10970
                 URL: https://issues.apache.org/jira/browse/SPARK-10970
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 1.5.1
         Environment: Hive 1.2, Spark on YARN
            Reporter: Cheolsoo Park
            Priority: Critical


This is a regression in Spark 1.5, more specifically after upgrading Hive 
dependency to 1.2.

HIVE-2573 introduced a new feature that allows users to register functions in 
session. The problem is that it added a [static code 
block|https://github.com/apache/hive/blob/branch-1.2/ql/src/java/org/apache/hadoop/hive/ql/metadata/Hive.java#L164-L170]
 to Hive.java-
{code}
// register all permanent functions. need improvement
static {
  try {
    reloadFunctions();
  } catch (Exception e) {
    LOG.warn("Failed to access metastore. This class should not accessed in 
runtime.",e);
  }
}
{code}
This code block is executed by every Spark executor in cluster when HadoopRDD 
tries to access to JobConf. So if Spark job has a high parallelism (eg 1000+), 
executors will hammer the HCat server causing it to go down in the worst case.

Here is the stack trace that I took in executor when it makes a connection to 
Hive metastore-
{code}
15/10/06 19:26:05 WARN conf.HiveConf: HiveConf of name hive.optimize.s3.query 
does not exist
15/10/06 19:26:05 INFO hive.metastore: XXX: 
java.lang.Thread.getStackTrace(Thread.java:1589)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.metastore.HiveMetaStoreClient.<init>(HiveMetaStoreClient.java:236)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient.<init>(SessionHiveMetaStoreClient.java:74)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
java.lang.reflect.Constructor.newInstance(Constructor.java:526)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.metastore.MetaStoreUtils.newInstance(MetaStoreUtils.java:1521)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.<init>(RetryingMetaStoreClient.java:86)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.getProxy(RetryingMetaStoreClient.java:132)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.getProxy(RetryingMetaStoreClient.java:104)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.metadata.Hive.createMetaStoreClient(Hive.java:3005)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.metadata.Hive.getMSC(Hive.java:3024)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.metadata.Hive.getAllDatabases(Hive.java:1234)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.metadata.Hive.reloadFunctions(Hive.java:174)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.metadata.Hive.<clinit>(Hive.java:166)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.plan.PlanUtils.configureJobPropertiesForStorageHandler(PlanUtils.java:803)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.hadoop.hive.ql.plan.PlanUtils.configureInputJobPropertiesForStorageHandler(PlanUtils.java:782)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.sql.hive.HadoopTableReader$.initializeLocalJobConfFunc(TableReader.scala:347)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.sql.hive.HadoopTableReader$anonfun$17.apply(TableReader.scala:322)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.sql.hive.HadoopTableReader$anonfun$17.apply(TableReader.scala:322)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.HadoopRDD$anonfun$getJobConf$6.apply(HadoopRDD.scala:179)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.HadoopRDD$anonfun$getJobConf$6.apply(HadoopRDD.scala:179)
15/10/06 19:26:05 INFO hive.metastore: XXX: scala.Option.map(Option.scala:145)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.HadoopRDD.getJobConf(HadoopRDD.scala:179)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.HadoopRDD$anon$1.<init>(HadoopRDD.scala:231)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.HadoopRDD.compute(HadoopRDD.scala:227)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.HadoopRDD.compute(HadoopRDD.scala:103)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:297)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:297)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:297)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.UnionRDD.compute(UnionRDD.scala:97)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:297)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.MapPartitionsWithPreparationRDD.compute(MapPartitionsWithPreparationRDD.scala:63)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:297)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:297)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.rdd.RDD.iterator(RDD.scala:264)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:73)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.scheduler.Task.run(Task.scala:88)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:214)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
15/10/06 19:26:05 INFO hive.metastore: XXX: 
java.lang.Thread.run(Thread.java:745)
15/10/06 19:26:05 INFO hive.metastore: Trying to connect to metastore with URI 
thrift://admin.gateway.dataeng.netflix.net:11002
{code}
As can be seen, HadoopRDD tries to get JobConf in executor, which in turn 
invokes the {{reloadFunctions()}} function in Hive.java.

What's worse, due to HIVE-10319, a single {{reloadFunctions()}} call ends up 
making hundreds of thrift calls to Hive metastore if there are a large number 
of databases in Hive metastore. So any Spark job can easily take down HCat 
server in production.

As a workaround, I forked Databrick's [Hive 1.2 
repo|https://github.com/pwendell/hive/commits/release-1.2.1-spark], removed the 
static code block from Hive.java, and rebuilt Spark with this forked version of 
Hive. I don't know if there is a better way of fixing this problem.



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