R has been available for Windows since the very beginning, but if you have a Windows machine and want to use R within a Linux ecosystem, that’s easy to do with the new Fall Creator’s Update (version 1709). If you need access to the gcc toolchain for building R packages, or simply prefer the bash environment, it’s easy to get things up and running.
Once you have things set up, you can launch a bash shell and run R at the terminal like you would in any Linux system. And that’s because this is a Linux system: the Windows Subsystem for Linux is a complete Linux distribution running within Windows. This page provides the details on installing Linux on Windows, but here are the basic steps you need and how to get the latest version of R up and running within it.
Click through for a quick tutorial.
Mssql-cli is a new and interactive command line tool that provides the following key enhancements over sqlcmd in the Terminal environment:
- T-SQL IntelliSense
- Syntax highlighting
- Pretty formatting for query results, including Vertical Format
- Multi-line edit mode
- Configuration file support
Mssql-cli aims to offer an improved interactive command line experience for T-SQL. It is fully open source under the BSD-3 license, and a contribution to the dbcli organization, an open source suite of interactive CLI tools for relational databases including SQL Server, PostgresSQL, and MySQL. The command-line UI is written in Python and the tool leverages the same microservice backend (sqltoolsservice) that powers the VS Code SQL extension, SQL Operations Studio, and the other Python CLI tool we announced earlier, mssql-scripter.
Something very cool that Alan points out is that this is “the first time our team is contributing source code to an existing open source organization with a commitment to be a good citizen in an existing open source community.”
In our Oracle environment, we can see every background process, with it’s own pid and along with the process monitor, (pmon)db writer, (dbwr), log writer, (lgwr), we also have archiving, (arcx), job processing, (j00x) performance and other background processing. I didn’t even grep for the Oracle executable, so you recognize how quickly we can see what is running.
In the SQL Server environment, we only have two processes- our parent process is PID 7 and the child is 9 for SQL Server and nothing to distinguish what they actually are doing. If we decide to use the pmap utility to view what the parent and child process aredoing, we see only sqlservr as the mapping information.
I imagine that things like this will improve over time for SQL Server, but Oracle definitely has a leg up in this regard.
There was a question this morning on the SQL Server Community Slack channel from SvenLowry about how to launch SQL Server on Linux in Single User Mode. Well you’ve heard everyone say, it’s just SQL Server…and that’s certainly true and this is another example of that idea.
The command line parameters from the sqlservr binary are passed through into the SQLPAL managed Win32 SQL Process. So let’s check out how to do this together…
Click through for a demo.
With the new install of Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-87-generic x86_64), different attempts at installing SQL Server resulted in the error: “E: Unable to locate package mssql-server”.
Read on for the solution.
Now in the output above, you’ll notice a bolded line. In there, you can system that systemd receives a return code from SQL Server of status=1/FAILURE. Systemd is the parent process to sqlservr, in fact it’s the parent to all processes on our system. It receives the exit code and immediately, systemd initiates a restart of the service due to the configuration we have for our mysql-server systemd unit.What’s interesting is that this happens even on a normal shutdown. But that simply doesn’t make sense, return values on clean exits should return 0. It’s my understanding of the SHUTDOWN command, that it will cause the database engine to shutdown cleanly.
On the development side, there aren’t many differences between SQL on Linux versus SQL on Windows (aside from things which haven’t yet made the move); on the administration side, there are some interesting differences.
Jan said that he had gotten the SQL Agent running in Linux containers so I asked if he could send on his code and he very kindly obliged.
So, the disclaimer for this blog post is that I didn’t write the code here, Jan did. All I’ve done is drop it into a dockerfile so that an image can be built. Thank you very much Jan!
Click through for Jan’s code and Andrew’s presentation of the process.
We can use tools like ps, top and htop to look our are virtual and physical memory allocations. We can also look in the /proc virtual file system for our process and look at the status file. In here we’ll find the point in time status of a process, and most importantly the types of memory allocations for a process. We’ll get granular data on the virtual memory allocations and also the resident set size of the process. Here are the interesting values in the status file we’re going to focus on today.
VmSize – total current virtual address space of the process
VmRSS – total amount of physical memory currently allocated to the process
VmSwap – total amount of virtual memory currently paged out to the swap file (disk)
The differences are going to be interesting for people to troubleshoot later, particularly if you look at SOS_SCHEDULER_YIELD and give a knee-jerk reaction that the problem is with CPU.
When an index rebuild was kicked off on a large table (around 25GB), the reindex operation terminated, and the availability group had failed over to the other replica.
Upon further investigation, we discovered that the SQL Server process terminated at the time reindex operation was run and this resulted in the failover.
To determine the reason for the unexpected shutdown, we reviewed the Linux System Logs (/var/log/messages on RHEL) & pacemaker logs. From the pacemaker logs and system logs, we saw entries indicating that oom-killer was invoked, and as a result SQL Server process was terminated.
Read on for the two solutions. I was hoping for a solution that involved making the SQL Server executable immune from oom-killer’s wily ways, but not so much in this post.
Before we start though, there’s a few things you’re going to need to have already set up:
An Active Directory Domain to test in, and rights to administer it. Since we’re going to be creating (and possibly deleting, if there are errors) computer objects and a service account, you’ll need a domain account with adequate permissions.
My example assumes you have a Microsoft DNS server running alongside your domain services. It is possible to use a separate DNS server to get this to work, but you might need some additional network configuration (see below). Also, depending on your environment, you might need a reverse lookup zone defined. If you notice long ping times or other weird lookups, I’d set one up in your DNS.
A machine (virtual or otherwise) that is running CentOS 7 or later (and this guide was written and tested against CentOS 7). For this demo, we’ll be using the Server (minimal install) installation option. If you’re new to Linux, you might opt a desktop version (server with a GUI). When you download a CentOS disk image to install it, you get all these options on the default media; you won’t need separate downloads
There are a few more prereqs, so read the whole thing. This route is easier than Ubuntu, as Drew notes.