[jira] [Created] (HIVE-17146) Spark on Hive - Exception while joining tables - "Requested replication factor of 10 exceeds maximum of x"

["George Smith (JIRA)" <ji...@apache.org>]

George Smith created HIVE-17146:
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             Summary: Spark on Hive - Exception while joining tables - "Requested replication factor of 10 exceeds maximum of x" 
                 Key: HIVE-17146
                 URL: https://issues.apache.org/jira/browse/HIVE-17146
             Project: Hive
          Issue Type: Bug
          Components: Hive
    Affects Versions: 2.1.1, 3.0.0
            Reporter: George Smith


We found a bug in the current implementation of [org.apache.hadoop.hive.ql.exec.SparkHashTableSinkOperator|https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/SparkHashTableSinkOperator.java]

The *magic number 10* for minReplication factor can causes the exception when the configuration parameter _dfs.replication_ is lower than 10. 

Consider these [properties configuration|https://hadoop.apache.org/docs/r2.7.2/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml] on cluster:
{code}
dfs.namenode.replication.min=1
dfs.replication=2
dfs.replication.max=512 (that's the default value)
{code}
The current implementation counts target file replication as follows (relevant snippets of the code):
{code}
private int minReplication = 10;
...
int dfsMaxReplication = hconf.getInt(DFS_REPLICATION_MAX, minReplication);
    // minReplication value should not cross the value of dfs.replication.max
minReplication = Math.min(minReplication, dfsMaxReplication);
...
FileSystem fs = path.getFileSystem(htsOperator.getConfiguration());
short replication = fs.getDefaultReplication(path);
...
int numOfPartitions = replication;
replication = (short) Math.max(minReplication, numOfPartitions);
//use replication value in fs.create(path, replication);
{code}


With a current code the used replication value is 10 and the config value _dfs.replication_ is not used at all.

There are probably more (easy) ways to fix it:
# Set field  {code}private int minReplication = 1 ; {code} I don't see any obvious reason for the value 10.    or
# Init minReplication from config value _dfs.namenode.replication.min_ with a default value 1. or
# Count replication this way: {code}replication = Math.min(numOfPartitions, dfsMaxReplication);{code} or
# Use replication = numOfPartitions; directly
Config value _dfs.replication_ has a default value 3 which is supposed to be always lower than "dfs.replication.max", no checking is probably needed.



As a *workaround* for this issue we had to set dfs.replication.max=2, but obviously _dfs.replication_ value should NOT be ignored and the problem should be resolved.







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