Posts Categorized: Technical Blog

Free Apache Cassandra Training Event in Cambridge, MA March 23

cambridge

I’ll be speaking, along with DataStax and Microsoft representatives, at Cassandra Essentials Day this coming Monday (March 23) in Cambridge. MA. This free training event will cover the basics of Apache Cassandra, and show you how to try it out quickly, easily, and free of charge on the Azure cloud. Expect to learn about the unique aspects of Cassandra and DataStax Enterprise, and to dive into real-world use cases.

Using strace to debug application errors in linux

strace is a very useful tool which traces system calls and signals for a running process. This helps a lot while debugging application level performance issues and bugs. Aim of this post is to demonstrate the power of strace in pinning down an application bug. I came across an issue in which nagios was sending…

Monitoring Cassandra with Grafana and Influx DB

Grafana_cassandra-test2

Hello, In this post I will explain how to set up Cassandra monitoring with influxDB and Grafana. This can also be used to connect to other monitoring systems (Graphite, Collectd, etc…) but since both influxDB and Grafana are hot topics at the moment I decided to follow the trend! I was asked why I was…

Detecting Source of MySQL Queries with Comments

As a MySQL DBA I already know the data changes that happen on my system. I have logs for that. However, it’s a common problem that several years into the life of an application, the current developers won’t know where in the codebase queries come from. It’s often hard for them to find the location…

Performance Problems with Dynamic Statistics in Oracle 12c

I’ve been making some tests recently with the new Oracle 12.1.0.2 In-Memory option and have been faced with an unexpected  performance problem.  Here is a test case: Waiting for in-memory segment population: Now let’s make a simple two table join: Query runs pretty fast. Execution plan has the brand new vector transformation After having such…

Troubleshooting a Multipath Issue

Multipathing allows to configure multiple paths from servers to storage arrays. It provides I/O failover and load balancing. Linux uses device mapper kernel framework to support multipathing. In this post I will explain the steps taken to troubleshoot a multipath issue. This should provide an glimpse into the tools and technology involved. Problem was reported…

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