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Category: Administration

Receiving Notifications on Cosmos DB 429 Errors

Published 2021-08-31 by Kevin Feasel

Hasan Savran wants to remain in the loop:

Developers like to know when things go wrong in applications. It is an easy and simple solution to send an email when a bad error occurs. Things can go wrong easily in Cosmos Db, one of the most common error you will get from Cosmos DB is “Request rate too large (429)” exception. This error says that you do not have enough request units to run a query. This error usually occurs in peak times. Usually cause of getting 429 errors is the configuration of Request Units settings. You need to scale up your application or optimize your queries.
     It takes more time to retrieve data from Cosmos DB when error 429 occurs. You should get notification when this occurs, but you do not want to get an email each time it occurs either. 1- 5% of requests with 429 is acceptable. You can always open the Cosmos DB Monitoring tools and keep eye on it, or you can create Cosmos DB Alerts to get emails.

Click through for a demonstration of how to use Cosmos DB Alerts.

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Contrasting In-Place and Side-By-Side Updates for SQL Server

Published 2021-08-31 by Kevin Feasel

Chad Callihan is not the biggest fan of in-place upgrades:

How many SQL Server upgrades have you been a part of? Was there much discussion about whether or not to do an in-place upgrade versus a side-by-side upgrade? I’ve been part of both and to me there is only one safe way to perform upgrades. Let’s go over some pros and cons of each and see if you come to the same conclusion.

I did kind of spoil the answer, but click through to understand why one is so much riskier than the other.

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E-Mailing a DBA upon Object Creation in System Databases

Published 2021-08-30 by Kevin Feasel

Thomas Williams has another script for us:

Next on the list to commission a SQL Server, is to create a trigger in the master system database to send an e-mail to the DBA when objects are created in the database.

In general I’d expect this never to happen – but if it did, I’d want to follow up. It’s possible to go even further and prevent creating objects in the master system database completely.

My experience is that about 5% of the time, people intentionally put objects into the master database, and 95% of the time, I…err, they…forgot to switch databases before running the script.

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SQL Server Monitoring via Zabbix

Published 2021-08-26 by Kevin Feasel

Reitse Eskens digs into using Zabbix to monitor SQL Server:

In one of the projects I’m working in, we needed to have some sort of monitoring solution on SQL Server, but there wasn’t budget for a commercial monitoring solution. There’s a small number of freeware, open-source solutions but these are all difficult to get working. In this blog I’ll show you what Zabbix has on offer as a default and what you can add yourself.

I’m not the biggest fan of Zabbix, but if it’s what you have, better to use the tools you have than not.

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Dealing with Non-Yielding Schedulers

Published 2021-08-26 by Kevin Feasel

Sean Gallardy breaks up the party:

One of the most common items that will cause a memory dump in SQL Server is a non-yielding scheduler (generally referred to as NYS). What the heck does that mean? Why would it cause a memory dump? Is there anything that can be investigated? Good questions, let’s take a look.

Read on to learn what these are, why they’re not something you want to deal with on a regular basis, and how you can get more information on what happened out of a dump file. Which is also going to be helpful for Microsoft staff to diagnose and correct the underlying issue (if possible).

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Sending an E-Mail upon Database Creation

Published 2021-08-24 by Kevin Feasel

Thomas Williams has a job for SQL Server:

As part of commissioning a SQL Server, I create a server trigger to send an e-mail when a new database is created (adapted from https://www.mssqltips.com/sqlservertip/2864/email-alerts-when-new-databases-are-created-in-sql-server/), and a SQL Agent alert which e-mails when a database is restored (inspired by Jeremy Dearduff’s comment at https://www.brentozar.com/archive/2017/06/tracking-restores-hard/#comment-2446362).

After receiving the e-mail I can follow up and include the database in an inventory. See below for the trigger and alert scripts – feel free to use these as a basis for your own monitoring and inventory.

Click through for the script, as well as an important disclaimer.

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Changing the Slow Query Log Threshold in RDS

Published 2021-08-20 by Kevin Feasel

John McCormack wants to know about those slow queries:

The slow query log will record all queries which are above the threshold level. The default value is 10 (seconds) but you can set it higher or lower depending on your requirements. It is useful for finding slow queries and allows you to pick out candidates for tuning.

If you set the threshold too low, it can increase I/O overhead on your instance and use a lot of valuable disk space. If you set it too high, it might not capture enough useful information.

This is a setting in AWS Relational Database Services and mimics functionality in MySQL

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Projecting Disk Space Available

Published 2021-08-20 by Kevin Feasel

Constantine Kokkinos predicts the future:

The first question I wanted to model out was a bigger issue with on-premises databases – when are we going to run out of storage?

Back in the day I’d cheat with msdb backups, comparing compressed sized to actuals, and moving on. However I don’t have a historical reference for Stack Overflow… so what can I do?

Taking a look at the tables we see a commonality in many tables – CreationDate! It looks like the rows faithfully are stamped when they are created.

Constantine does at the end hit on something we tend to forget: most operations in life aren’t quite linear. We often get lucky in that certain stretches are close enough to be linear that we can model them that way, but even in this dataset, you can see the effects of polynomial growth slowly build up. Still, this is a good way of taking us through what an analysis and projection can look like.

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When Did That SQL Server Start?

Published 2021-08-20 by Kevin Feasel

Chad Callihan breaks out the stopwatch:

When you are troubleshooting query performance, it’s important to consider when SQL Server last restarted. Each time SQL Server restarts, buffer pool and plan cache get wiped out. This can play a big part in how you approach an issue.

You want to know how much history you have to work with. Not seeing much data in plan cache? Maybe SQL Server restarted recently. Parameter sniffing issues that you were seeing earlier today are now suddenly “fixed?” SQL Server could have restarted between then and now. Let’s take a quick look a few ways to review how long SQL Server has been up and running.

Click through for several techniques. I’ve always checked the tempdb startup time in sys.databases, myself, but that’s not the only way.

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Fixing Hadoop Namenodes in Safe Mode

Published 2021-08-16 by Kevin Feasel

The Hadoop in Real World team doesn’t need to play it safe:

When namenode is started or restarted, namenode will be in safemode for a period of time. At this time you will not be able to use your Hadoop cluster fully. Write operations to HDFS will fail and because of that your MapReduce jobs will also fail.

Read on for other reasons why the namenode might be stuck in safe mode and what you can do to fix it.

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