Press "Enter" to skip to content

Category: Hadoop

Checking Spark Config on Windows

Published 2019-08-29 by Kevin Feasel

Ed Elliott has a Powershell script to tell you if your Spark configuration on Windows is incorrect:

There are some pretty common mistakes people make (myself included!), most common I have seen recently have been having a semi-colon in JAVA_HOME/SPARK_HOME/HADOOP_HOME or having HADOOP_HOME not point to a directory with a bin folder which contains winutils.

To help, I have written a small powershell script that a) validates that the setup is correct and then b) runs one of the spark examples to prove that everything is setup correctly.

Click through for the script.

Comments closed

Apache Flink 1.9 Released

Published 2019-08-27 by Kevin Feasel

The Apache Flink crew announces version 1.9.0:

The Apache Flink project’s goal is to develop a stream processing system to unify and power many forms of real-time and offline data processing applications as well as event-driven applications. In this release, we have made a huge step forward in that effort, by integrating Flink’s stream and batch processing capabilities under a single, unified runtime.

Significant features on this path are batch-style recovery for batch jobs and a preview of the new Blink-based query engine for Table API and SQL queries. We are also excited to announce the availability of the State Processor API, which is one of the most frequently requested features and enables users to read and write savepoints with Flink DataSet jobs. Finally, Flink 1.9 includes a reworked WebUI and previews of Flink’s new Python Table API and its integration with the Apache Hive ecosystem.

Click through for the major changes.

Comments closed

Working with Tables in Databricks

Published 2019-08-27 by Kevin Feasel

Brad Llewellyn shows us how to build tables (temporary and permanent) and views in Azure Databricks using each of the main languages:

Simply put, an External Table is a table built directly on top of a folder within a data source.  This means that the data is not hidden away in some proprietary SQL format.  Instead, the data is completely accessible to outside systems in its native format.  The main reason for this is that it gives us the ability to create “live” queries on top of text data sources.  Every time a query is executed against the table, the query is run against the live data in the folder.  This means that we don’t have to run ETL jobs to load data into the table.  Instead, all we need to do is put the structured files in the folder and the queries will automatically surface the new data.

Each language has its own way of doing things, but they all use the Hive metastore under the covers.

Comments closed

Configuring an Azure Databricks Cluster

Published 2019-08-26 by Kevin Feasel

Jon Gurgul explains cluster settings in Azure Databricks:

We need compute to run our notebooks and this is achieved by creating a cluster. A cluster is merely a number of Virtual Machines behind the scenes used to form this compute resource. The benefit of Azure Databricks is that compute is only chargeable when on.

Let’s now click the Clusters icon and set up a simple cluster. Once you have loaded the page you can use the “Create Cluster” button.

Click through for an explanation of what each of the settings means.

Comments closed

The Basics of Apache Airflow

Published 2019-08-26 by Kevin Feasel

Divyansh Jain explains what Apache Airflow is and takes us through a sample solution:

Airflow is a platform to programmatically author, schedule & monitor workflows or data pipelines. These functions achieved with Directed Acyclic Graphs (DAG) of the tasks. It is an open-source and still in the incubator stage. It was initialized in 2014 under the umbrella of Airbnb since then it got an excellent reputation with approximately 800 contributors on GitHub and 13000 stars. The main functions of Apache Airflow is to schedule workflow, monitor and author.

It’s another interesting product in the Hadoop ecosystem and has additional appeal outside of that space.

Comments closed

Comparing Performance: HBase1 vs HBase2

Published 2019-08-23 by Kevin Feasel

Surbhi Kochhar takes us through performance improvements between HBase version 1 and HBase version 2:

We are loading the YCSB dataset with 1000,000,000 records with each record 1KB in size, creating total 1TB of data. After loading, we wait for all compaction operations to finish before starting workload test. Each workload tested was run 3 times for 15min each and the throughput* measured. The average number is taken from 3 tests to produce the final number. 

The post argues that there’s an improvement, but when a majority of cases end up worse (even if just a little bit), I’m not sure it’s much of an improvement.

Comments closed

The Transaction Log in Delta Tables

Published 2019-08-23 by Kevin Feasel

Burak Yavuz, et al, explain how the transaction log works with Delta Tables in Apache Spark:

When a user creates a Delta Lake table, that table’s transaction log is automatically created in the _delta_log subdirectory. As he or she makes changes to that table, those changes are recorded as ordered, atomic commits in the transaction log. Each commit is written out as a JSON file, starting with 000000.json. Additional changes to the table generate subsequent JSON files in ascending numerical order so that the next commit is written out as 000001.json, the following as 000002.json, and so on.

It’s interesting that they chose JSON instead of a binary transaction log like relational databases use.

Comments closed

Spark for .NET Developers

Published 2019-08-23 by Kevin Feasel

Ed Elliott has a long-form post covering spark-dotnet:

The .NET driver is made up of two parts, and the first part is a Java JAR file which is loaded by Spark and then runs the .NET application. The second part of the .NET driver runs in the process and acts as a proxy between the .NET code and .NET Java classes (from the JAR file) which then translate the requests into Java requests in the Java VM which hosts Spark.

The .NET driver is added to a .NET program using NuGet and ships both the .NET library as well as two Java jars. One jar is for Spark 2.3 and one for Spark 2.4, and you do need to use the correct one on your installed version of Scala.

As much as I’ve enjoyed his series, getting it in a single-post format is great.

Comments closed

Debugging Spark Applications in Visual Studio

Published 2019-08-22 by Kevin Feasel

Ed Elliott continues a series on spark-dotnet:

There are two approaches, one I have used for years with dotnet when I want to debug something that is challenging to get a debugger attached – think apps which spawn other processes and they fail in the startup routine. You can add a Debugger.Launch() to your program then when spark executes it, a prompt will be displayed and you can attach Visual Studio to your program. (as an aside I used to do this manually a lot by writing an __asm int 3 into an app to get it to break at an appropriate point, great memories but we don’t need to do that anymore luckily :).

The second approach is to start the spark-dotnet driver in debug mode which instead of launching your app, it starts and listens for incoming requests – you can then run your program as normal (f5), set a breakpoint and your breakpoint will be hit.

Read on to see how it’s done, as well as a possibly-accidental benefit to this.

Comments closed

Performance Tuning Neural Network Training

Published 2019-08-20 by Kevin Feasel

Sean Owen takes us through a few techniques for speeding up neural network model training:

Step #2: Use Early Stopping
Keras (and other frameworks) have built-in support for stopping when further training appears to be making the model worse. In Keras, it’s the EarlyStopping callback. Using it means passing the validation data to the training process for evaluation on every epoch. Training will stop after several epochs have passed with no improvement. restore_best_weights=True ensures that the final model’s weights are from its best epoch, not just the last one. This should be your default.

Sean focuses here on Keras + TensorFlow on Spark, but several of the tips are cross-product and generally applicable.

Comments closed