Jupyter On ElasticMapReduce

Tom Zeng shows howt o install Jupyter Notebooks on Amazon’s ElasticMapReduce:

By default (with no --password and --port arguments), Jupyter will run on port 8888 with no password protection; JupyterHub will run on port 8000.  The --port and --jupyterhub-port arguments can be used to override the default ports to avoid conflicts with other applications.

The --r option installs the IRKernel for R. It also installs SparkR and sparklyr for R, so make sure Spark is one of the selected EMR applications to be installed. You’ll need the Spark application if you use the --toree argument.

If you used --jupyterhub, use Linux users to sign in to JupyterHub. (Be sure to create passwords for the Linux users first.)  hadoop, the default admin user for JupyterHub, can be used to set up other users. The –password option sets the password for Jupyter and for the hadoop user for JupyterHub.

Installation is fairly straightforward, and they include a series of samples you can get to try out Jupyter.

Optimistic Locking Via HTTP ETags

Kevin Sookocheff diagrams how to implement optimistic concurrency for a server which uses HTTP requests to handle resources like files:

A conditional request is a request that may be executed differently depending on the value of specific HTTP headers. These headers define the precondition that must be true before the server should execute the request. With respect to entity tags, we have two options for making requests conditional.

  1. If-Match: The request will succeed if the ETag of the remote resource is equal to the one listed in this header.
  2. If-None-Match: The request will succeed if the ETag of the remote resource is different to each listed in this header.

By specifying the appropriate ETag and condition header, you can perform optimistic locking for concurrent operations on a resource. Let’s walk through an example of how this works in practice.

Read on for more details.

Linux Data Science Virtual Machine

David Smith mentions the Linux data science virtual machine on Azure:

The Linux Data Science Virtual Machine includes all of the tools a modern data scientist needs, in one easy-to-launch package. With it, you can try exploring data with Apache Drill, train deep neural networks for computer vision with MXNet, develop AI applications with the Cognitive Toolkit, or create statistical models with big data in R with Microsoft R Server 9.0.

They also offer a free trial, so check it out.

Blocked Process Report

Kendra Little has a few Github gists showing how to configure the blocked process report:

I wanted a friendly way to share code to configure and manage the Blocked Process Report, so I’ve created a gist on GitHub sharing TSQL that:

  • Enables the Blocked Process Report (BPR)

  • Collects the BPR with an Extended Events trace

  • Collects the BPR using a Server Side SQL Trace (in case you don’t care XEvents or are running an older version of SQL Server)

  • Lists out the Extended Events and SQL Traces you have running, and gives you code to stop and delete traces if you wish

Click through for the code.

REPLACENULL

Louis Davidson shows a quick SSIS function to replace NULL values:

Which I looked up every..single..time I used it. “?” means THEN…not IF? “:” means ELSE? Huh?  I know this comes from one of those cool languages that I have never mastered, but as I was searching for the syntax again a few days ago, I found REPLACENULL. I had never seen this function before, so I figured I might not be the only one. And perhaps if a commenter feels like telling me how dumb I am to not know about other new expression features I will not be offended. REPLACENULL won’t replace every use of the these and the other symbols one must use for SSIS expressions, it does replace one of the more common ones.

Click through for usage.  It’s a bit easier to understand than the ternary operator.  To answer Louis’s question, a ? b : c comes from C# syntax.

When Is NOLOCK Okay?

Kevin Feasel

2016-12-23

T-SQL

Erik Darling wants to figure out the acceptable boundaries for NOLOCK:

Picture a couple developers who started their app in the cloud, where they can’t get fancy with tempdb, fast disks aren’t in the budget yet, along with that beefier server with some extra RAM. They may not be able to turn on RCSI or SI at the drop of a hat; tempdb would keel over with the row versioning as part of a workload that already uses it pretty heavily.

They still need to run reports, either for users, or for higher ups at the company, and they can ask for them at any time. Caching the data when user activity is low and reporting against it when someone asks may raise some questions, like “why doesn’t my sales data show anything from today?”, or worse. You could invalidate the cache every X minutes, but that doesn’t help because then you need to re-run that reporting query every X minutes. That’s only moderately better than letting users query it at will.

Figuring out when read uncommitted is acceptable is a business decision.  As much as I dislike using NOLOCK, as long as the people on the business side understand the risks, it’s their call.

Loading SMO In Powershell

Chrissy LeMaire shows how to load SMO with full names when you don’t know which version is installed:

In a recent version of PowerShell, Publish-Module, which publishes modules to the Gallery began requiring fully qualified Assembly names such as “Microsoft.SqlServer.Smo, Version=$smoversion, Culture=neutral, PublicKeyToken=89845dcd8080cc91”.

Previously, it was sufficient just to use short names such as Microsoft.SqlServer.Smo. This had similar behavior to LoadWithPartialName.

I get that LoadWithPartialName is sketchy, but the solution that Chrissy has to do seems overly complicated to me.  Nonetheless, those are the rules of the game now, I suppose.

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