How to read Druid data using JDBC driver with spark? - apache-spark

Question

How can I read data from Druid using spark and Avatica JDBC Driver?
This is avatica JDBC document
Reading data from Druid using python and Jaydebeapi module, I succeed like below code.
$ python
import jaydebeapi
conn = jaydebeapi.connect("org.apache.calcite.avatica.remote.Driver",
"jdbc:avatica:remote:url=http://0.0.0.0:8082/druid/v2/sql/avatica/",
{"user": "druid", "password":"druid"},
"/root/avatica-1.17.0.jar",
)
cur = conn.cursor()
cur.execute("SELECT * FROM INFORMATION_SCHEMA.TABLES")
cur.fetchall()
output is:
[('druid', 'druid', 'wikipedia', 'TABLE'),
('druid', 'INFORMATION_SCHEMA', 'COLUMNS', 'SYSTEM_TABLE'),
('druid', 'INFORMATION_SCHEMA', 'SCHEMATA', 'SYSTEM_TABLE'),
('druid', 'INFORMATION_SCHEMA', 'TABLES', 'SYSTEM_TABLE'),
('druid', 'sys', 'segments', 'SYSTEM_TABLE'),
('druid', 'sys', 'server_segments', 'SYSTEM_TABLE'),
('druid', 'sys', 'servers', 'SYSTEM_TABLE'),
('druid', 'sys', 'supervisors', 'SYSTEM_TABLE'),
('druid', 'sys', 'tasks', 'SYSTEM_TABLE')] -> default tables
But I want to read using spark and JDBC.
I tried it but there is a problem using spark like below code.
$ pyspark --jars /root/avatica-1.17.0.jar
df = spark.read.format('jdbc') \
.option('url', 'jdbc:avatica:remote:url=http://0.0.0.0:8082/druid/v2/sql/avatica/') \
.option("dbtable", 'INFORMATION_SCHEMA.TABLES') \
.option('user', 'druid') \
.option('password', 'druid') \
.option('driver', 'org.apache.calcite.avatica.remote.Driver') \
.load()
output is:
Traceback (most recent call last):
File "<stdin>", line 8, in <module>
File "/root/spark-2.4.4-bin-hadoop2.7/python/pyspark/sql/readwriter.py", line 172, in load
return self._df(self._jreader.load())
File "/root/spark-2.4.4-bin-hadoop2.7/python/lib/py4j-0.10.7-src.zip/py4j/java_gateway.py", line 1257, in __call__
File "/root/spark-2.4.4-bin-hadoop2.7/python/pyspark/sql/utils.py", line 63, in deco
return f(*a, **kw)
File "/root/spark-2.4.4-bin-hadoop2.7/python/lib/py4j-0.10.7-src.zip/py4j/protocol.py", line 328, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o2999.load.
: java.sql.SQLException: While closing connection
...
Caused by: java.lang.RuntimeException: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "rpcMetadata" (class org.apache.calcite.avatica.remote.Service$CloseConnectionResponse), not marked as ignorable (0 known properties: ])
at [Source: {"response":"closeConnection","rpcMetadata":{"response":"rpcMetadata","serverAddress":"172.18.0.7:8082"}}
; line: 1, column: 46]
...
Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "rpcMetadata" (class org.apache.calcite.avatica.remote.Service$CloseConnectionResponse), not marked as ignorable (0 known properties: ])
at [Source: {"response":"closeConnection","rpcMetadata":{"response":"rpcMetadata","serverAddress":"172.18.0.7:8082"}}
; line: 1, column: 46]
...
Note:
I downloaded Avatica jar file(avatica-1.17.0.jar) from maven-repository
I installed Druid server using docker-compose and default setting values.

Answer 1

I found another way to solve this problem. I used spark-druid-connector to connect druid with spark.
But I changed some codes like this to use this code for my environment.
This is my environment:
spark: 2.4.4
scala: 2.11.12
python: python 3.6.8
druid:
zookeeper: 3.5
druid: 0.17.0
However, it has a problem.
If you use spark-druid-connector at least once, all sql queries like spark.sql("select * from tmep_view") used from the following will be entered into this planner.
but, if you use dataframe's api like df.distinct().count(), then there are no problems. I didn't solve yet.

Answer 2

I tried with spark-shell:
./bin/spark-shell --driver-class-path avatica-1.17.0.jar --jars avatica-1.17.0.jar
val jdbcDF = spark.read.format("jdbc")
.option("url", "jdbc:avatica:remote:url=http://0.0.0.0:8082/druid/v2/sql/avatica/")
.option("dbtable", "INFORMATION_SCHEMA.TABLES")
.option("user", "druid")
.option("password", "druid")
.load()