Streamline data processing has become an inherent part of a modern data architecture build on top of Hadoop. Big Data applications need to act on data being ingested at a high rate and volume in real time. Sensor data, logs and other events likely have the most value when being analyst at the time they are emited – in real time.
For over 6 years Apache Storm has matured at hundreds of global companies to the preferred stream processing engine on top of Hadoop. In a more recent approach Spark Streaming was published build around Spark‘s Resilient Distributed Datasets (RDD). Constructed with the same concepts as Spark, a in-memory batch compute enginge, Spark Streaming is offering the clear advantage of bringing batch and real time processing closer together, as ideally the same code base can be leveraged for both.
Hence Spark Streaming is a so called micro-batching framework that uses timed intervals. It uses so called D-Streams (Discretized Stream) that structure computation as small sets of short, stateless, and deterministic tasks. State is distributed and stored in fault-tolerant RDDs. A D-Stream can be build from various data sources as Kafka, Flume, or HDFS offering many of the same operations available for RDDs with additional operations typical for time operations such as sliding windows.
In this post we are looking at a fairly basic example of using Spark Streaming. We will listen to a server emitting line by line in this example. Continue reading “Spark Streaming – A Simple Example”
With the release of Hive 0.13.1 and HCatalog, a new Streaming API was released as a Technical Preview to support continuous data ingestion into Hive tables. This API is intended to support streaming clients like Flume or Storm to better store data in Hive, which traditionally has been a batch oriented storage.
Based on the newly given ACID insert/update capabilities of Hive, the Streaming API is breaking down a stream of data into smaller batches which get committed in a transaction to the underlying storage. Once committed the data becomes immediately available for other queries.
Broadly speaking the API consists of two parts. One part is handling the transaction while the other is dealing with the underlying storage (HDFS). Transactions in Hive are handled by the the Metastore. Kerberos is supported from the beginning!
Some of the current limitations are:
- Only delimited input data and JSON (strict syntax) are supported
- Only ORC support
- Hive table must be bucketed (unpartitioned tables are supported)
In this post I would like to demonstrate the use of a newly created Storm HiveBolt that makes use of the streaming API and is quite straightforward to use. The source of the here described example is provided at GitHub. To run this demo you would need a HDP 2.2 Sandbox, which can be downloaded for various virtualization environments here. Continue reading “Hive Streaming with Storm”
If you are using Python with Hadoop Streaming a lot then you might know about the trouble of keeping all nodes up to date with required packages. A nice way to work around this is to use Virtualenv for each streaming project. Besides the hurdle of keeping all nodes in sync with the necessary libraries another advantage of using Virtualenv is the possibility to try different versions and setups within the same project seamlessly.
In this example we are going to create a Python job that counts the n-grams of hotel names in relation to the country the hotel is located in. Besides the use of a Virtualenv where we install NLTK, we are going to strive the use of Avro as an input for a Python streaming job, as well as secondary sorting with the use of
KeyFieldBasedComparator . Continue reading “Python Virtualenv with Hadoop Streaming”