Developing Applications With Apache Kudu

Several example applications are provided in the examples directory of the Apache Kudu git repository. Each example includes a README that shows how to compile and run it. The following list includes some of the examples that are available today. Check the repository itself in case this list goes out of date.

cpp/example.cc

A simple C++ application which connects to a Kudu instance, creates a table, writes data to it, then drops the table.

java/java-example

A simple Java application which connects to a Kudu instance, creates a table, writes data to it, then drops the table.

java/insert-loadgen

A small Java application which listens on a TCP socket for time series data corresponding to the Collectl wire protocol. The commonly-available collectl tool can be used to send example data to the server.

python/dstat-kudu

A Java application that generates random insert load.

python/graphite-kudu

An example program that shows how to use the Kudu Python API to load data into a new / existing Kudu table generated by an external program, dstat in this case.

python/graphite-kudu

An example plugin for using graphite-web with Kudu as a backend.

These examples should serve as helpful starting points for your own Kudu applications and integrations.

The following Maven <dependency> element is valid for the Apache Kudu GA release:

<dependency>
  <groupId>org.apache.kudu</groupId>
  <artifactId>kudu-client</artifactId>
  <version>1.1.0</version>
</dependency>

Convenience binary artifacts for the Java client and various Java integrations (e.g. Spark, Flume) are also now available via the ASF Maven repository and the Central Maven repository.

To build the Java client, clone the Kudu Git repository, change to the java directory, and issue the following command:

$ mvn install -DskipTests

For more information about building the Java API, as well as Eclipse integration, see java/README.md.

The Kudu Python client provides a Python friendly interface to the C++ client API.

To install and use Kudu Python client, you need to install the Kudu C++ client libraries and headers. See Setting Up Apache Kudu Using the Command Line for installing Kudu C++ client.

The sample below demonstrates the use of part of the Python client.

import kudu
from kudu.client import Partitioning
from datetime import datetime

# Connect to Kudu master server
client = kudu.connect(host='kudu.master', port=7051)

# Define a schema for a new table
builder = kudu.schema_builder()
builder.add_column('key').type(kudu.int64).nullable(False).primary_key()
builder.add_column('ts_val', type_=kudu.unixtime_micros, nullable=False, compression='lz4')
schema = builder.build()

# Define partitioning schema
partitioning = Partitioning().add_hash_partitions(column_names=['key'], num_buckets=3)

# Create new table
client.create_table('python-example', schema, partitioning)

# Open a table
table = client.table('python-example')

# Create a new session so that we can apply write operations
session = client.new_session()

# Insert a row
op = table.new_insert({'key': 1, 'ts_val': datetime.utcnow()})
session.apply(op)

# Upsert a row
op = table.new_upsert({'key': 2, 'ts_val': "2016-01-01T00:00:00.000000"})
session.apply(op)

# Updating a row
op = table.new_update({'key': 1, 'ts_val': ("2017-01-01", "%Y-%m-%d")})
session.apply(op)

# Delete a row
op = table.new_delete({'key': 2})
session.apply(op)

# Flush write operations, if failures occur, capture print them.
try:
    session.flush()
except kudu.KuduBadStatus as e:
    print(session.get_pending_errors())

# Create a scanner and add a predicate
scanner = table.scanner()
scanner.add_predicate(table['ts_val'] == datetime(2017, 1, 1))

# Open Scanner and read all tuples
# Note: This doesn't scale for large scans
result = scanner.open().read_all_tuples()

See Using Apache Impala with Kudu for guidance on installing and using Impala with Kudu, including several impala-shell examples.

Kudu integrates with Spark through the Data Source API as of version 1.0.0. Include the kudu-spark dependency using the --packages option:

Spark 1.x - Use the kudu-spark_2.10 artifact if you are using Spark 1.x with Scala 2.10:

spark-shell --packages org.apache.kudu:kudu-spark_2.10:1.1.0

Spark 2.x - Use the kudu-spark2_2.11 artifact if you are using Spark 2.x with Scala 2.11:

spark2-shell --packages org.apache.kudu:kudu-spark2_2.11:1.4.0

Then import kudu-spark and create a dataframe as demonstrated in the following sample code. In the following example, replace <kudu.master> with the actual hostname of the host running a Kudu master service, and <kudu_table> with the name of a pre-existing table in Kudu.

import org.apache.kudu.spark.kudu._

// Read a table from Kudu 
val df = spark.sqlContext.read.options(Map("kudu.master" -> "<kudu.master>:7051","kudu.table" -> "<kudu_table>")).kudu

// Query <kudu_table> using the Spark API...
df.select("id").filter("id" >= 5).show()

// ...or register a temporary table and use SQL
df.registerTempTable("<kudu_table>")
val filteredDF = sqlContext.sql("select id from <kudu_table> where id >= 5").show()

// Use KuduContext to create, delete, or write to Kudu tables
val kuduContext = new KuduContext("<kudu.master>:7051", sqlContext.sparkContext)

// Create a new Kudu table from a dataframe schema
// NB: No rows from the dataframe are inserted into the table
kuduContext.createTable("test_table", df.schema, Seq("key"), new CreateTableOptions().setNumReplicas(1))

// Insert data
kuduContext.insertRows(df, "test_table")

// Delete data
kuduContext.deleteRows(filteredDF, "test_table")

// Upsert data
kuduContext.upsertRows(df, "test_table")

// Update data
val alteredDF = df.select("id", $"count" + 1)
kuduContext.updateRows(filteredRows, "test_table"

// Data can also be inserted into the Kudu table using the data source, though the methods on KuduContext are preferred
// NB: The default is to upsert rows; to perform standard inserts instead, set operation = insert in the options map
// NB: Only mode Append is supported
df.write.options(Map("kudu.master"-> "<kudu.master>:7051", "kudu.table"-> "test_table")).mode("append").kudu

// Check for the existence of a Kudu table
kuduContext.tableExists("another_table")

// Delete a Kudu table
kuduContext.deleteTable("unwanted_table")

Kudu was designed to integrate with MapReduce, YARN, Spark, and other frameworks in the Hadoop ecosystem. See RowCounter.java and ImportCsv.java for examples which you can model your own integrations on.