Developing Applications With Apache Kudu
Apache Kudu provides C++ and Java client APIs, as well as reference examples to illustrate their use. A Python API is included, but it is currently considered experimental, unstable, and is subject to change at any time.
Viewing the API Documentation
C++ API Documentation
The documentation for the C++ client APIs is included in the header files in /usr/include/kudu/ if you installed Kudu using packages or subdirectories of src/kudu/client/ if you built Kudu from source. If you installed Kudu using parcels, no headers are included in your installation. and you will need to build Kudu from source in order to have access to the headers and shared libraries.
$ find /usr/include/kudu -type f -name *.h
Java API Documentation
View the Java API documentation online. Alternatively, after building the Java client, Java API documentation is available in java/kudu-client/target/apidocs/index.html.
Kudu Example Applications
- java-example
- A simple Java application which connects to a Kudu instance, creates a table, writes data to it, then drops the table.
- java/collectl
- A simple 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.
- java/insert-loadgen
-
A Java application that generates random insert load.
- python/dstat-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 experimental plugin for using graphite-web with Kudu as a backend.
- demo-vm-setup
- Scripts to download and run a VirtualBox virtual machine with Kudu already installed. For more information see the Kudu Quickstart documentation.
These examples should serve as helpful starting points for your own Kudu applications and integrations.
Maven Artifacts
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.
Building the Java Client
- JDK 7
- Apache Maven 3.x
- protoc 2.6 or newer installed in your path, or built from the thirdparty/ directory. Run the following commands to build
protoc from the third-party dependencies:
thirdparty/download-thirdparty.sh thirdparty/build-thirdparty.sh protobuf
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.
Kudu Python Client
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.
- Install Cython: sudo pip install cython
- Downloaded the Kudu Python client from kudu-python: kudu-python-1.2.0.tar.gz
- Install kudu-python: sudo pip install kudu-python
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()
Example Apache Impala Commands With Kudu
See Using Apache Impala with Kudu for guidance on installing and using Impala with Kudu, including several impala-shell examples.
Kudu Integration with Spark
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")
Using Spark with a Secure Kudu cluster
The Kudu-Spark integration is able to operate on secure Kudu clusters which have authentication and encryption enabled, but the submitter of the Spark job must provide the proper credentials. For Spark jobs using the default 'client' deploy mode, the submitting user must have an active Kerberos ticket granted through kinit. For Spark jobs using the 'cluster' deploy mode, a Kerberos principal name and keytab location must be provided through the --principal and --keytab arguments to spark2-submit.
Spark Integration Known Issues and Limitations
Integration with MapReduce, YARN, and Other Frameworks
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.
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