GitHub user HyukjinKwon opened a pull request:
https://github.com/apache/spark/pull/19845
[SPARK-22651][PYTHON][ML] Prevent initiating multiple Hive clients for
ImageSchema.readImages
## What changes were proposed in this pull request?
Calling `ImageSchema.readImages` multiple times as below:
```python
from pyspark.ml.image import ImageSchema
data_path = 'data/mllib/images/kittens'
_ = ImageSchema.readImages(data_path, recursive=True,
dropImageFailures=True).collect()
_ = ImageSchema.readImages(data_path, recursive=True,
dropImageFailures=True).collect()
```
throws an error as below:
```
...
org.datanucleus.exceptions.NucleusDataStoreException: Unable to open a test
connection to the given database. JDBC url =
jdbc:derby:;databaseName=metastore_db;create=true, username = APP. Terminating
connection pool (set lazyInit to true if you expect to start your database
after your app). Original Exception: --
java.sql.SQLException: Failed to start database 'metastore_db' with class
loader org.apache.spark.sql.hive.client.IsolatedClientLoader$$anon$1@742f639f,
see the next exception for details.
...
at org.apache.derby.jdbc.AutoloadedDriver.connect(Unknown Source)
...
at
org.apache.hadoop.hive.metastore.HiveMetaStore.newRetryingHMSHandler(HiveMetaStore.java:5762)
...
at
org.apache.spark.sql.hive.client.HiveClientImpl.newState(HiveClientImpl.scala:180)
...
at
org.apache.spark.sql.SparkSession.createDataFrame(SparkSession.scala:348)
at
org.apache.spark.ml.image.ImageSchema$$anonfun$readImages$2$$anonfun$apply$1.apply(ImageSchema.scala:253)
...
Caused by: ERROR XJ040: Failed to start database 'metastore_db' with class
loader org.apache.spark.sql.hive.client.IsolatedClientLoader$$anon$1@742f639f,
see the next exception for details.
at org.apache.derby.iapi.error.StandardException.newException(Unknown
Source)
at
org.apache.derby.impl.jdbc.SQLExceptionFactory.wrapArgsForTransportAcrossDRDA(Unknown
Source)
... 121 more
Caused by: ERROR XSDB6: Another instance of Derby may have already booted
the database /.../spark/metastore_db.
...
Traceback (most recent call last):
File "", line 1, in
File "/.../spark/python/pyspark/ml/image.py", line 190, in readImages
dropImageFailures, float(sampleRatio), seed)
File "/.../spark/python/lib/py4j-0.10.6-src.zip/py4j/java_gateway.py",
line 1160, in __call__
File "/.../spark/python/pyspark/sql/utils.py", line 69, in deco
raise AnalysisException(s.split(': ', 1)[1], stackTrace)
pyspark.sql.utils.AnalysisException: u'java.lang.RuntimeException:
java.lang.RuntimeException: Unable to instantiate
org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient;'
```
Seems we better stick to `SparkSession.builder.getOrCreate()` like:
https://github.com/apache/spark/blob/51620e288b5e0a7fffc3899c9deadabace28e6d7/python/pyspark/sql/streaming.py#L329
https://github.com/apache/spark/blob/dc5d34d8dcd6526d1dfdac8606661561c7576a62/python/pyspark/sql/column.py#L541
https://github.com/apache/spark/blob/33d43bf1b6f55594187066f0e38ba3985fa2542b/python/pyspark/sql/readwriter.py#L105
## How was this patch tested?
This was tested as below:
```python
from pyspark.ml.image import ImageSchema
data_path = 'data/mllib/images/kittens'
_ = ImageSchema.readImages(data_path, recursive=True,
dropImageFailures=True).collect()
_ = ImageSchema.readImages(data_path, recursive=True,
dropImageFailures=True).collect()
```
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/HyukjinKwon/spark SPARK-22651
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/19845.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #19845
commit c0c3c487474629df00ba50c5b6904552010f1aab
Author: hyukjinkwon
Date: 2017-11-29T13:17:24Z
Prevent initiating multiple Hive clients for ImageSchema.readImages
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