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.
PostgreSQL High Availability Options: Why PostgreSQL High Availability Matters and How to Achieve It
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.
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.
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).
The Pound program is a reverse proxy, load balancer and HTTPS front-end for Web server(s). Pound was developed to enable distributing the load among several Web-servers and to allow for a convenient SSL wrapper for those Web servers that do not offer it natively. Pound is distributed under the GPL - no warranty, it's free to use, copy and give away.
WHAT POUND IS:
a reverse-proxy: it passes requests from client browsers to one or more back-end servers.
a load balancer: it will distribute the requests from the client browsers among several back-end servers, while keeping session information.
an SSL wrapper: Pound will decrypt HTTPS requests from client browsers and pass them as plain HTTP to the back-end servers.
an HTTP/HTTPS sanitizer: Pound will verify requests for correctness and accept only well-formed ones.
a fail over-server: should a back-end server fail, Pound will take note of the fact and stop passing requests to it until it recovers.
a request redirector: requests may be distributed among servers according to the requested URL.Pound is a very small program, easily audited for security problems. It can run as setuid/setgid and/or in a chroot jail. Pound does not access the hard-disk at all (except for reading the certificate file on start, if required) and should thus pose no security threat to any machine.
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.