cowsql (/ˈkaʊ,siːkwəl/ listen) is a C library that implements an embeddable and replicated SQL database engine with high availability and automatic failover.

cowsql extends SQLite with a network protocol that can connect together various instances of your application and have them act as a highly-available cluster, with no dependency on external databases.

The name "cowsql" loosely refers to the "pets vs. cattle" concept, since it's generaly fine to delete or rebuild a particular node of an application that uses cowsql for data storage.

A Guide to PostgreSQL High Availability

Ensuring your application can handle failures and outages is crucial, and the availability of your application is only as good as the availability of your PostgreSQL instance. With that in mind, you may be wondering which PostgreSQL high availability (HA) deployment option is best for your application.

Let’s review several popular solutions that increase the high availability of PostgreSQL deployments and, as a result, the availability overall of your application. Why several and not one? Well, there’s no silver bullet or one-size-fits-all solution when it comes to high availability and PostgreSQL. So, walk through the options for a highly available deployment of PostgreSQL and then you can make a choice that fits your use case.

• pgpool Wiki
• patroni/patroni: A template for PostgreSQL High Availability with Etcd, Consul, ZooKeeper, or Kubernetes

orchestrator is a MySQL high availability and replication management tool, runs as a service and provides command line access, HTTP API and Web interface. orchestrator supports:

‍Consensus algorithms in their theoretical and applied forms can be difficult to reason about. Often, these algorithms are solutions that have stumbled upon some good problems to solve. Unfortunately, the problems are evolving. And I don’t think these solutions are going to remain relevant much longer. Let’s start with defining the problems they solve:

Distributed Durability: In case of node failures, your data is guaranteed to be elsewhere.
Availability: The ability for the system to continue serving if some nodes have become unavailable.
Automation: If there is a failure, the system knows how to remedy itself without human intervention.

Some months ago, Shlomi Noah published a series about Service Discovery. In his posts, Shlomi describes many ways for an application to find the master. He also gives detail on how these solutions cope with failover to a slave, including their integration with Orchestrator.

This is a great series, and I recommend its reading for everybody implementing master failover, with or without Orchestrator, and even if you are not fully automating the process yet. Taking a step back, I realized that service discovery is only one of the five parts of a full MySQL Master Failover Strategy, and this post is about these five parts. In some follow-up posts, I might analyze some deployments using the framework presented in this post.

This is the first in a series of posts reviewing methods for MySQL master discovery: the means by which an application connects to the master of a replication tree. Moreover, the means by which, upon master failover, it identifies and connects to the newly promoted master.

These posts are not concerned with the manner by which the replication failure detection and recovery take place. I will share orchestrator specific configuration/advice, and point out where cross DC orchestrator/raft setup plays part in discovery itself, but for the most part any recovery tool such as MHA, replication-manager, severalnines or other, is applicable.

We discuss asynchronous (or semi-synchronous) replication, a classic single-master-multiple-replicas setup. A later post will briefly discuss synchronous replication (Galera/XtraDB Cluster/InnoDB Cluster).

We use PostgreSQL extensively at Braintree, and it backs many of our highly available services (including our main payments API).

We are constantly building and refining our products, and this often means evolving our database schema. In general, PostgreSQL is great at this, and we can make many different types of schema changes without downtime. There are some gotchas, however, that this post will cover.

This page explains two different approaches to setting up a highly available Kubernetes cluster using kubeadm:

With stacked masters. This approach requires less infrastructure. etcd members and control plane nodes are co-located.
With an external etcd cluster. This approach requires more infrastructure. The control plane nodes and etcd members are separated.

Your clusters must run Kubernetes version 1.11 or later. You should also be aware that setting up HA clusters with kubeadm is still experimental. You might encounter issues with upgrading your clusters, for example. We encourage you to try either approach, and provide feedback.

If you have questions, join us on the kubernetes slack, channel #kubespray.

• Can be deployed on AWS, GCE, Azure, OpenStack, vSphere, Oracle Cloud Infrastructure (Experimental), or Baremetal
• Highly available cluster
• Composable (Choice of the network plugin for instance)
• Supports most popular Linux distributions
• Continuous integration tests

RTKLIB is an open source program package for standard and precise positioning with GNSS (global navigation satellite system). RTKLIB consists of a portable program library and several APs (application programs) utilizing the library.

Die für Positionsbestimmungen mit hoher Genauigkeit (Sub-Meter bis Zentimeter) erforderlichen GNSS-Empfänger mit Trägerphasen-Messung sind in der Praxis üblicherweise mehrfrequenzfähig
(zumeist L1+L2), im Markt jedoch so teuer, dass potenzielle Anwender häufig bereits an den
Investitionskosten für die Hardware scheitern. Diverse L1-Empfänger mit Trägerphasen-Rohdatenausgabe
sind aber relativ günstig erhältlich und z.B. für RTK bzw. eine Postprozessierung mit eigenen
oder externen Referenzdaten sogar i.V. mit kostenfreier Software nutzbar, unterliegen
allerdings dabei auch einigen technischen Einschränkungen. Gleichwohl sind auf Basis dieser
kostengünstigen Komponenten auch komplette Systeme bereits in praxistauglicher Weise realisierbar.

Hagen F. Piotraschke

How to set up the ISC DHCP daemon with load sharing and failover capabilities.

Setting Up DHCP Failover: A Basic Overview
Many of the syntax options presented here are explained in more detain in the dhcpd.conf man page distributed with dhcp. It is recommended that you consult that document for specifics once you have grasped the basic steps involved.

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