Distributing TensorFlow

While at it’s core TensorFlow is a distributed computation framework besides the official HowTo there is little detailed documentation around the way TensorFlow deals with distributed learning. This post is an attempt to learn by example about TensorFlow’s distribution capabilities. Therefor the existing MNIST tutorial is taken and adapted into a distributed execution graph that can be executed on one or multiple nodes.

The framework offers two basic ways for distributed training of a model. In the simplest form the same data and computation graph is executed on multiple nodes in parallel on batches of the replicated data. This is known as Between-Graph Replication. Each worker updates the parameters of the same model, which means that each of the worker nodes are sharing a model. Updates to the shared model get averaged before being applied, this is at least the case for the synchronous training of a distributed model. In case of an asynchronous training the workers update the shared model parameters independently of each other. While the asynchronous training is known to be faster, the synchronous training proofs to provide more accuracy.
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YARN Secure Container

In a restricted setup YARN executes task of computation frameworks like Spark in a secured Linux or Window Container. The task are being executed in the local context of the user submitting the application and are not being executed in the local context of the yarn or some other system user. With this come certain constraints for the system setup.

How is YARN actually able to impersonate the calling user on the local OS level? This posts aims to give some background information to help answer such questions about secure containers. Only Linux systems are considered here, no Windows.

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TensorFlow: Further Reading

Some collection of papers and work around deep distributed learning to deepen once understanding in that topic:

Large Scale Distributed Deep Networks (link) (December, 2012)
Jeffrey Dean, Greg S. Corrado, Rajat Monga, Kai Chen, Matthieu Devin, Quoc V. Le, Mark Z. Mao, Marc’Aurelio Ranzato, Andrew Senior, Paul Tucker, Ke Yang, Andrew Y. Ng

This paper published, among other contributes, by Jeffrey Dean together with Andrew NG probably marks the cornerstone to TensorFlow as it is today.

Efficient Estimation of Word Representations in Vector Space (link) (Januar 2013)
Tomas Mikolov, Kai Chen, Greg Corrado, Jeffrey Dean

The fundamental work around projects like Word2Vec is presented in this paper, where vector representation of words for similarity trained by a neural net is being described.

Sequence to Sequence Learning with Neural Networks (link) (September 2014)
Ilya Sutskever, Oriol Vinyals, Quoc V. Le

The work around sequence to sequence learning is actually quite old. Which seems like a fairly abstract problem to solve has recently proved to significantly improve for example speech to text recognition among other disciplines.

Show and Tell: A Neural Image Caption Generator (link) (November 2014)
Oriol Vinyals, Alexander Toshev, Samy Bengio, Dumitru Erhan

Another area were the above described concept of sequence to sequence learning is described is the exploration of images. In this case the input sequence is a bitmap of an image which is transferred to a text sequence describing the image. This marks a fundamental breakthrough in computer AI.

TensorFlow: Large-Scale Machine Learning on Heterogeneous Distributed Systems (link) (November 2015)
Martín Abadi, Ashish Agarwal, Paul Barham, Eugene Brevdo, Zhifeng Chen, Craig Citro, Greg S. Corrado, Andy Davis, Jeffrey Dean, Matthieu Devin, Sanjay Ghemawat, Ian Goodfellow, Andrew Harp, Geoffrey Irving, Michael Isard, Rafal Jozefowicz, Yangqing Jia, Lukasz Kaiser, Manjunath Kudlur, Josh Levenberg, Dan Mané, Mike Schuster, Rajat Monga, Sherry Moore, Derek Murray, Chris Olah, Jonathon Shlens, Benoit Steiner, Ilya Sutskever, Kunal Talwar, Paul Tucker, Vincent Vanhoucke, Vijay Vasudevan, Fernanda Viégas, Oriol Vinyals, Pete Warden, Martin Wattenberg, Martin Wicke, Yuan Yu, and Xiaoqiang Zheng

The TensorFlow Whitepaper [PDF]

Webinar: TensorFlow: A Framework for Scalable Machine Learning (link) (October 19, 2016)
Martin Wicke, Software Engineer at Google
Rajat Monga, Engineering Director at Google

Martin and Rajat, both software engineers for Google working on TensorFlow, walk through the architecture and design of TensorFlow throughout this webinar.


HDFS Storage Tier – Archiving to Cloud w/ S3

By default HDFS does not distinguish between different storage types hence making it difficult to optimize installations with heterogeneous storage devices. Since Hadoop 2.3 and the integration of HDFS-2832 HDFS supports placing block replicas on persistent tiers with different durability and performance requirements. Continue reading “HDFS Storage Tier – Archiving to Cloud w/ S3”

San Diego Brewery Field Trip

Recently I had the pleasure of traveling to San Diego the self-proclaimed American capital of Craft Beer. Of course I had to do a little research of my own while visiting this amazing city. Here is the short abstract of a tasteful field trip to some of the exceptional beer places in San Diego. Continue reading “San Diego Brewery Field Trip”

Installing HDP Search with Ambari

Ambari Management Packs are a new convenient way to integrate various services to the Ambari stack. As an example in this post we are using the Solr service mpack to install HDP on top of a newly installed cluster.

The HDP search mpack is available on the Hortonworks public repository for download. A mpack essentially is tar balls containing a mpack.json file specification and related binaries. Continue reading “Installing HDP Search with Ambari”

2016 in Numbers

Over two years ago in March 2014 I joined the Iron Blogger community in Munich, which is one of the largest, still active Iron Blogger communities worldwide. You can read more about my motivation behind it here in one of the 97 blog posts published to date: Iron Blogger: In for a Perfect Game.

The real fact is that I write blogs solely for myself. It’s my own technical reference I turn to. Additionally writing is a good way to improve once skills and technical capabilities, as Richard Guindon puts it in his famous quote:

“Writing is nature’s way of letting you know how sloppy your thinking is.”

What could be better suited to improve something than by leaning into the pain, how the great Aaron Swartz, who died way too early, once described it? And it is quite a bit of leaning into the pain publishing a blog post every week. Not only for me, but also for those close to me. But I am going to dedicate a separate blog post to a diligent retrospection in the near future. This post should all be about NUMBERS. Continue reading “2016 in Numbers”

Simple Spark Streaming & Kafka Example in a Zeppelin Notebook

Apache Zeppelin is a web-based, multi-purpose notebook for data discovery, prototyping, reporting, and visualization. With it’s Spark interpreter Zeppelin can also be used for rapid prototyping of streaming applications in addition to streaming-based reports.

In this post we will walk through a simple example of creating a Spark Streaming application based on Apache Kafka. Continue reading “Simple Spark Streaming & Kafka Example in a Zeppelin Notebook”

Kerberos Debug Notes

Some notes for Kerberos debugging in a secure HDP setup:

  1. Setting Debug Logs
    To enable debug logs in Java for Kerberos sun.security.krb5.debug needs to be set to true. Doing this for Hadoop can be done in the hadoop-env.sh file by adding it to the HADOOP_OPTS environment variable:

    Additionally the HADOOP_JAAS_DEBUG variable can be set also:

    Receiving traces in bash/shell can be enabled by setting the following environment variable:
  2. Testing auth_to_local Settings
    Setting the auth_to_local rules correclty can be quite crucial. This is especially true for KDS trust environments. The rules can be easily tested with the HadoopKerberosName call of Hadoop security. You can run it as:


Broadcast Join with Spark

With a broadcast join one side of the join equation is being materialized and send to all mappers. It is therefore considered as a map-side join which can bring significant performance improvement by omitting the required sort-and-shuffle phase during a reduce step. In this Post we are going to discuss the possibility for broadcast joins in Spark DataFrame and RDD API in Scala. Continue reading “Broadcast Join with Spark”