A New Way to Restore ClickHouse After ZooKeeper Metadata Is Lost

A New Way to Restore ClickHouse After ZooKeeper Metadata Is Lost

Every ClickHouse user has experienced data loss due to user error or operational failure with Zookeeper at least once in their lifetime. If a failure resulted in metadata loss, ClickHouse tables can turn into pumpkins–you can query but you cannot insert more data. But as of ClickHouse version 21.7, this has changed with a new SQL Command. Keep reading to learn more.

Webinar: Introduction to the Mysteries of ClickHouse Replication

Webinar: Introduction to the Mysteries of ClickHouse Replication

Built-in replication is a powerful ClickHouse feature that helps scale data warehouse performance as well as ensure high availability. This webinar will introduce how replication works internally, explain configuration of clusters with replicas, and show you how to set up and manage ZooKeeper, which is necessary for replication to function. We’ll finish off by showing useful replication tricks, such as utilizing replication to migrate data between hosts.

Webinar Slides: Introduction to the Mysteries of ClickHouse Replication

By Robert Hodges and Altinity Engineering Team
Slides for the Webinar, presented on July 31, 2019 
Webinar recording is available here

Built-in replication is a powerful ClickHouse feature that helps scale data warehouse performance as well as ensure high availability. This webinar will introduce how replication works internally, explain configuration of clusters with replicas, and show you how to set up and manage ZooKeeper, which is necessary for replication to function. We’ll finish off by showing useful replication tricks, such as utilizing replication to migrate data between hosts. Join us to become an expert in this important subject!

Realtime replication from MySQL to ClickHouse in practice

July 2, 2018
Vladislav Klimenko from Altinity and Valery Panov from Ivinco presented a talk at HighLoad Siberia 2018 conference recently. They described the real problem that Ivinco faced and how it has been solved with migration of analytics from MySQL into ClickHouse using MySQL to ClickHouse replication. A few months ago we introduced clickhouse-mysql tool in our blog, and Ivinco was the first company we know that tried it and used it in production.

Circular Replication Cluster Topology in ClickHouse

Circular Replication Cluster Topology in ClickHouse

In some cases, there is a need to configure a distributed cluster with replication but there are not enough servers in order to place every replica on a separate node. It is better to have multiple replicas at the same nodes configured in a special way, that allows to continue executing queries even in the case of a node failure. Such replication configuration can be found in different distributed systems, it is often referred to as ‘circular’ or ‘ring’ replication. In this article, we will discuss how to set up circular replication in ClickHouse.

Archiving MySQL Tables in ClickHouse

Archiving MySQL Tables in ClickHouse

Why Archive? Hard drives are cheap nowadays, but storing lots of data in MySQL is not practical and can cause all sorts of performance bottlenecks. 

In this article Percona’s blogger Alexander Rubin is talking about archiving MySQL tables in ClickHouse for storage and analytics.

ClickHouse Data Distribution

Jun 5, 2017   
ClickHouse data distribution and replication are fundamental techniques for building reliable and scalable ClickHouse systems. In this article we will explain how it works from the user perspective