Category Archives: Databases

A NoSQL database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases.
A relational database management system is a database management system based on the relational model of data.

PostgreSQL: FATAL: Peer authentication failed for user “name”
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11 September 2019

A quick note mainly for myself on how to enable remote access in PostgreSQL and create its database dump. An EC2-server moved to our AWS account with one website. During an attempt to connect to the PostgreSQL running on this host – the “FATAL: Peer authentication failed for user “name”” appears. And the same error… Read More: PostgreSQL: FATAL: Peer authentication failed for user “name”0 (0) »

Redis: main configuration parameters and performance tuning overview
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10 September 2019

Currently configuring Redis server as our backend caching service and during that wrote this post with some things to pay attention at in Redis config file. Shortly enough but with links to other posts or documentation. Let’s begin with the redis-benchmark utility. Will be installed alongside with Redis service, so can be used right after… Read More: Redis: main configuration parameters and performance tuning overview0 (0) »

SonarQube: solving “Unrecoverable indexation failures” and Elasticsearch “Disk watermark exceeded” errors
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29 August 2019

We are using SonarQube started from a Jenkins jobs. See more at SonarQube: running tests from Jenkins Pipeline in Docker. So, the SonarQube is started from the Jenkins – all good here, but inside SonarQube we can see errors: java.lang.IllegalStateException: Unrecoverable indexation failures: 1 errors among 1 requests at org.sonar.server.es.IndexingListener$1.onFinish(IndexingListener.java:39) at org.sonar.server.es.BulkIndexer.stop(BulkIndexer.java:122) … And host… Read More: SonarQube: solving “Unrecoverable indexation failures” and Elasticsearch “Disk watermark exceeded”… »

Redis: fork – Cannot allocate memory, Linux, virtual memory and vm.overcommit_memory
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28 August 2019

Currently, I’m configuring a Redis as a caching service for our application and during that, I faced with the question: do I need to set vm.overcommit_memory to the value 1, i.e. disable it – or not? The question is quite old for me, see The story, but only now I found time to get to… Read More: Redis: fork – Cannot allocate memory, Linux, virtual memory and… »

AWS RDS: “SQLSTATE[22001] – Data too long for column” using MariaDB 10.2
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8 August 2019

We have a PHP-application with the AWS RDS MariaDB as a backend. On the previously used 10.0 version all was good, but right after we upgraded to the MariaDB 10.2 – got errors during tests: PDOException: SQLSTATE[22001]: String data, right truncated: 1406 Data too long for column ‘name’ at row 1 in /data/projects/projectname/vendor/yiisoft/yii2/db/Command.php:1290 The first… Read More: AWS RDS: “SQLSTATE[22001] – Data too long for column” using… »

AWS: MariaDB RDS – kill: You are not owner of thread
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14 May 2019

We have AWS RDS with MariaDB. The error below and its solution aren’t specific to AWS RDS and MariaDB. The next error appears during attempt to kill() a thread in MySQL: [simterm] MariaDB [(none)]> kill 759; ERROR 1095 (HY000): You are not owner of thread 759 [/simterm] The solution is to use the mysql.rds_kill() procedure… Read More: AWS: MariaDB RDS – kill: You are not owner of… »

TestRail: reset admin password
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13 May 2019

We have a TestRail installation but suddenly lose its Admin user password. The Reset Password says that “Email sending failed” although email was configured and users are able to get emails from the server. Also, the log /var/www/testrail.example.com/logs/log-2019-05-13.php didn’t says anything so will reset password in another way – by update this TestRail MySQL database… Read More: TestRail: reset admin password0 (0) »

Redis: replication, part 4 – writing an Ansible role fore the Master-Slave replication with Redis Sentinel provisioning
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15 April 2019

The next post from the Redis replication series. Previous parts: Redis: replication, part 1 – an overview. Replication vs Sharding. Sentinel vs Cluster. Redis topology. Redis: replication, part 2 – Master-Slave replication, and Redis Sentinel Redis: replication, part 3 – redis-py and work with Redis Sentinel from Python The task now is to write an… Read More: Redis: replication, part 4 – writing an Ansible role fore… »

Redis: Sentinel – bind 0.0.0.0, the localhost issue and the announce-ip option
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10 April 2019

Originally, in a Sentinel’s configs, I have used the bind 0.0.0.0 to make them accessible from external hosts. Because of this when I started rolling out this setup on a real environment faced with an issue when Sentinels could not determine a Master host and other Sentinel hosts. In this post – such an issue… Read More: Redis: Sentinel – bind 0.0.0.0, the localhost issue and the… »

MySQL/MariaDB: like Petya ransomware for MySQL and ‘root’@’%’ access
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3 April 2019

This story happened on 10/06/2017, adding this post in English now. The original post (Rus) was written almost right after the well-known Not a Petya attack in Ukraine – that’s why it’s used in the title. I had a new project assigned to me. When I started its existing setup investigation – was just shocked.… Read More: MySQL/MariaDB: like Petya ransomware for MySQL and ‘root’@’%’ access0 (0) »