Replication

MongoDB Replica Set Scenarios and Internals – Part II (Elections)

mongodb node election to primary

In this blog post, we will walk through the internals of the election process in MongoDB®, following on from a previous post on the internals of the replica set. You can read Part 1 here.
For this post, I am refer to the same configurations we discussed before.
Elections: As the term suggests, in MongoDB there is a […]

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Replication Manager Works with MariaDB

Complex multi-cluster replication topology

Some time ago I wrote a script to manage asynchronous replication links between Percona XtraDB clusters. The original post can be found here. The script worked well with Percona XtraDB Cluster but it wasn’t working well with MariaDB®.  Finally, the replication manager works with MariaDB.
First, let’s review the purpose of the script. Managing replication […]

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PostgreSQL Streaming Physical Replication With Slots

postgres replication using slots

PostgreSQL streaming physical replication with slots simplifies setup and maintenance procedures. Usually, you should estimate disk usage for the Write Ahead Log (WAL) and provide appropriate limitation to the number of segments and setup of the WAL archive procedure. In this article, you will see how to use replication with slots and understand what problems […]

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MySQL High Availability: Stale Reads and How to Fix Them

solutions for MySQL Stale Reads

Continuing on the series of blog posts about MySQL High Availability, today we will talk about stale reads and how to overcome this issue.
The Problem
Stale reads is a read operation that fetches an incorrect value from a source that has not synchronized an update operation to the value (source Wiktionary).
A practical scenario is when […]

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Caveats With pt-table-checksum Using Row-Based Replication, and Replication Filters

pt-table-checksum row based replication caveat

As per the documentation, pt-table-checksum is a tool to perform online replication consistency checks by executing checksum queries on the master, which produces different results on replicas that are inconsistent with the master.
The master and each slave insert checksums into the percona.checksums table, and these are later compared for differences. It’s fairly obvious that […]

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How to Quickly Add a Node to an InnoDB Cluster or Group Replication

Quickly Add a Node in InnoDB Cluster or Group Replication

Quickly Add a Node to an InnoDB Cluster or Group Replication (Shutterstock)
In this blog, we’ll look at how to quickly add a node to an InnoDB Cluster or Group Replication using Percona XtraBackup.
Adding nodes to a Group Replication cluster can be easy (documented here), but it only works if the existing nodes have retained […]

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MongoDB Replica set Scenarios and Internals – Part 1

MongoDB replica sets replication internals r

The MongoDB® replica set is a group of nodes with one set as the primary node, and all other nodes set as secondary nodes. Only the primary node accepts “write” operations, while other nodes can only serve “read” operations according to the read preferences defined. In this blog post, we’ll focus on some MongoDB replica set scenarios, […]

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